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• dismissing uiwebview

  - by chimgrrl

  Ok, I really spend 2 days on this and it has gotten me stumped. From my main UIViewController I called a WebViewController which is a UIViewController with a UIWebView inside: UOLCategoriesWebViewController *ucwvcontroller = [[UOLCategoriesWebViewController alloc] initWithNibName:@"UOLCategoriesWebViewController" bundle:nil]; [self presentModalViewController:ucwvcontroller animated:YES]; [ucwvcontroller release]; Inside the UOLCategoriesWebViewController I've call the delegate method shouldStartLoadWithRequest where when the user clicks on a particular type of link it parses out the params and return back to the main UIViewController (or at least that's what I want it to do): - (BOOL)webView:(UIWebView*)webView shouldStartLoadWithRequest:(NSURLRequest*)request navigationType:(UIWebViewNavigationType)navigationType { BOOL continueOrExit = YES; NSURL *url = request.URL; NSString *urlString = [url relativeString]; NSString *urlParams = [url query]; NSArray *urlParamArr = [urlParams componentsSeparatedByString:@"&"]; NSLog(@"the url is: %@",urlString); //NSLog(@"the params are: %@,%@",[urlParamArr objectAtIndex:0],[urlParamArr objectAtIndex:1]); //BOOL endTrain1 = [[urlParamArr objectAtIndex:1] hasPrefix:@"subCatValue"]; //BOOL endTrain2 = ([urlParamArr objectAtIndex:1 //NSLog(@"Number of elements: %@",[urlParamArr count]); if (navigationType == UIWebViewNavigationTypeLinkClicked) { //NSLog(@"Enter into His glory"); if ([urlString hasSuffix:@"categories_list.php"]) { //NSLog(@"2nd Heaven"); continueOrExit = YES; }else if ([[urlParamArr objectAtIndex:1] hasPrefix:@"subCatValue"]) { continueOrExit = NO; NSLog(@"end of the train"); NSArray *firstParamStringArr = [[urlParamArr objectAtIndex:0] componentsSeparatedByString:@"="]; NSArray *secondParamStringArr = [[urlParamArr objectAtIndex:1] componentsSeparatedByString:@"="]; NSString *catSelected = [firstParamStringArr objectAtIndex:1]; NSString *subCatSelected = [secondParamStringArr objectAtIndex:1]; //go back to native app [self goBackToMain:catSelected andSubCat:subCatSelected]; } } return continueOrExit; } Actually in the above function where I am calling the goBackToMain method I want it to call the delegate method and return to the mainviewcontroller. Unfortunately after executing that goBackToMain method it goes back to this method and continue to return continueOrExit. Is there anyway to make it truly exit without returning anything? I've tried putting in multiple returns to no avail. Or can I in the html page pass some javascript to directly call this method so that I don't have to go through this delegate method? Thanks for the help in advance!

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• Identifying if a user is in the local administrators group

  - by Adam Driscoll

  My Problem I'm using PInvoked Windows API functions to verify if a user is part of the local administrators group. I'm utilizing GetCurrentProcess, OpenProcessToken, GetTokenInformationand LookupAccountSid to verify if the user is a local admin. GetTokenInformation returns a TOKEN_GROUPS struct with an array of SID_AND_ATTRIBUTES structs. I iterate over the collection and compare the user names returned by LookupAccountSid. My problem is that, locally (or more generally on our in-house domain), this works as expected. The builtin\Administrators is located within the group membership of the current process token and my method returns true. On another domain of another developer the function returns false. The LookupAccountSid functions properly for the first 2 iterations of the TOKEN_GROUPS struct, returning None and Everyone, and then craps out complaining that "A Parameter is incorrect." What would cause only two groups to work correctly? The TOKEN_GROUPS struct indicates that there are 14 groups. I'm assuming it's the SID that is invalid. Everything that I have PInvoked I have taken from an example on the PInvoke website. The only difference is that with the LookupAccountSid I have changed the Sid parameter from a byte[] to a IntPtr because SID_AND_ATTRIBUTESis also defined with an IntPtr. Is this ok since LookupAccountSid is defined with a PSID? LookupAccountSid PInvoke [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)] static extern bool LookupAccountSid( string lpSystemName, IntPtr Sid, StringBuilder lpName, ref uint cchName, StringBuilder ReferencedDomainName, ref uint cchReferencedDomainName, out SID_NAME_USE peUse); Where the code falls over for (int i = 0; i < usize; i++) { accountCount = 0; domainCount = 0; //Get Sizes LookupAccountSid(null, tokenGroups.Groups[i].SID, null, ref accountCount, null, ref domainCount, out snu); accountName2.EnsureCapacity((int) accountCount); domainName.EnsureCapacity((int) domainCount); if (!LookupAccountSid(null, tokenGroups.Groups[i].SID, accountName2, ref accountCount, domainName, ref domainCount, out snu)) { //Finds its way here after 2 iterations //But only in a different developers domain var error = Marshal.GetLastWin32Error(); _log.InfoFormat("Failed to look up SID's account name. {0}", new Win32Exception(error).Message); continue; } If more code is needed let me know. Any help would be greatly appreciated.

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• Why is my (Type).GetFields(BindingFlags.Instance | BindingFlags.Public) not working?

  - by granadaCoder

  My code can see the NonPublic members, but not the Public ones. (???) Full sample code below. FieldInfo[] publicFieldInfos = t.GetFields(BindingFlags.Instance | BindingFlags.Public); is returning nothing. Note, I'm trying to get at the properties on the abstract class as well as the 1 concrete class. (And read the attributes as well). I'm going bonkers on this one....the msdn example works with the 2 flags (BindingFlags.Instance | BindingFlags.Public).....but my mini inheritance example below is not. THANKS in advance. /////////////START CODE private void RunTest1() { try { textBox1.Text = string.Empty; Type t = typeof(MyInheritedClass); //Look at the BindingFlags *** NonPublic *** int fieldCount = 0; while (null != t) { fieldCount += t.GetFields(BindingFlags.Instance | BindingFlags.NonPublic).Length; FieldInfo[] nonPublicFieldInfos = t.GetFields(BindingFlags.Instance | BindingFlags.NonPublic); foreach (FieldInfo field in nonPublicFieldInfos) { if (null != field) { Console.WriteLine(field.Name); } } t = t.BaseType; } Console.WriteLine("\n\r------------------\n\r"); //Look at the BindingFlags *** Public *** t = typeof(MyInheritedClass); FieldInfo[] publicFieldInfos = t.GetFields(BindingFlags.Instance | BindingFlags.Public); foreach (FieldInfo field in publicFieldInfos) { if (null != field) { Console.WriteLine(field.Name); object[] attributes = field.GetCustomAttributes(t, true); if (attributes != null && attributes.Length > 0) { foreach (Attribute att in attributes) { Console.WriteLine(att.GetType().Name); } } } } } catch (Exception ex) { ReportException(ex); } } private void ReportException(Exception ex) { Exception innerException = ex; while (innerException != null) { Console.WriteLine(innerException.Message + System.Environment.NewLine + innerException.StackTrace + System.Environment.NewLine + System.Environment.NewLine); innerException = innerException.InnerException; } } public abstract class MySuperType { public MySuperType(string st) { this.STString = st; } public string STString { get; set; } public abstract string MyAbstractString {get;set;} } public class MyInheritedClass : MySuperType { public MyInheritedClass(string ic) : base(ic) { this.ICString = ic; } [Description("This is an important property"),Category("HowImportant")] public string ICString { get; set; } private string _oldSchoolPropertyString = string.Empty; public string OldSchoolPropertyString { get { return _oldSchoolPropertyString; } set { _oldSchoolPropertyString = value; } } [Description("This is a not so importarnt property"), Category("HowImportant")] public override string MyAbstractString { get; set; } }

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• What are the Rails best practices for javascript templates in restful/resourceful controllers?

  - by numbers1311407

  First, 2 common (basic) approaches: # returning from some FoosController method respond_to do |format| # 1. render the javascript directly format.js { render :json => @foo.to_json } # 2. render the default template, say update.js.erb format.js { render } end # in update.js.erb $('#foo').html("<%= escape_javascript(render(@foo)) %>") These are obviously simple cases but I wanted to illustrate what I'm talking about. I believe that these are also the cases expected by the default responder in rails 3 (either the action-named default template or calling to_#{format} on the resource.) The Issues With 1, you have total flexibility on the view side with no worries about the template, but you have to manipulate the DOM directly via javascript. You lose access to helpers, partials, etc. With 2, you have partials and helpers at your disposal, but you're tied to the one template (by default at least). All your views that make JS calls to FoosController use the same template, which isn't exactly flexible. Three Other Approaches (none really satisfactory) 1.) Escape partials/helpers I need into javascript beforehand, then inserting them into the page after, using string replacement to tailor them to the results returned (subbing in name, id, etc). 2.) Put view logic in the templates. For example, looking for a particular DOM element and doing one thing if it exists, another if it does not. 3.) Put logic in the controller to render different templates. For example, in a polymorphic belongs to where update might be called for either comments/foo or posts/foo, rendering commnts/foos/update.js.erb versus posts/foos/update.js.erb. I've used all of these (and probably others I'm not thinking of). Often in the same app, which leads to confusing code. Are there best practices for this sort of thing? It seems like a common enough use-case that you'd want to call controllers via Ajax actions from different views and expect different things to happen (without having to do tedious things like escaping and string-replacing partials and helpers client side). Any thoughts?

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• Magento - How to select mysql rows by max value?

  - by Damodar Bashyal

  mysql> SELECT * FROM `log_customer` WHERE `customer_id` = 224 LIMIT 0, 30; +--------+------------+-------------+---------------------+-----------+----------+ | log_id | visitor_id | customer_id | login_at | logout_at | store_id | +--------+------------+-------------+---------------------+-----------+----------+ | 817 | 50139 | 224 | 2011-03-21 23:56:56 | NULL | 1 | | 830 | 52317 | 224 | 2011-03-27 23:43:54 | NULL | 1 | | 1371 | 136549 | 224 | 2011-11-16 04:33:51 | NULL | 1 | | 1495 | 164024 | 224 | 2012-02-08 01:05:48 | NULL | 1 | | 2130 | 281854 | 224 | 2012-11-13 23:44:13 | NULL | 1 | +--------+------------+-------------+---------------------+-----------+----------+ 5 rows in set (0.00 sec) mysql> SELECT * FROM `customer_entity` WHERE `entity_id` = 224; +-----------+----------------+---------------------------+----------+---------------------+---------------------+ | entity_id | entity_type_id | email | group_id | created_at | updated_at | +-----------+----------------+---------------------------+----------+---------------------+---------------------+ | 224 | 1 | [email protected] | 3 | 2011-03-21 04:59:17 | 2012-11-13 23:46:23 | +-----------+----------------+---------------------------+----------+--------------+----------+-----------------+ 1 row in set (0.00 sec) How can i search for customers who hasn't logged in for last 10 months and their account has not been updated for last 10 months. I tried below but failed. $collection = Mage::getModel('customer/customer')->getCollection(); $collection->getSelect()->joinRight(array('l'=>'log_customer'), "customer_id=entity_id AND MAX(l.login_at) <= '" . date('Y-m-d H:i:s', strtotime('10 months ago')) . "'")->group('e.entity_id'); $collection->addAttributeToSelect('*'); $collection->addFieldToFilter('updated_at', array( 'lt' => date('Y-m-d H:i:s', strtotime('10 months ago')), 'datetime'=>true, )); $collection->addAttributeToFilter('group_id', array( 'neq' => 5, )); Above tables have one customer for reference. I have no idea how to use MAX() on joins. Thanks UPDATE: This seems returning correct data, but I would like to do magento way using resource collection, so i don't need to do load customer again on for loop. $read = Mage::getSingleton('core/resource')->getConnection('core_read'); $sql = "select * from ( select e.*,l.login_at from customer_entity as e left join log_customer as l on l.customer_id=e.entity_id group by e.entity_id order by l.login_at desc ) as l where ( l.login_at <= '".date('Y-m-d H:i:s', strtotime('10 months ago'))."' or ( l.created_at <= '".date('Y-m-d H:i:s', strtotime('10 months ago'))."' and l.login_at is NULL ) ) and group_id != 5"; $result = $read->fetchAll($sql); I have loaded full shell script to github https://github.com/dbashyal/Magento-ecommerce-Shell-Scripts/blob/master/shell/suspendCustomers.php

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• A question about making a C# class persistant during a file load

  - by Adam

  Apologies for the indescriptive title, however it's the best I could think of for the moment. Basically, I've written a singleton class that loads files into a database. These files are typically large, and take hours to process. What I am looking for is to make a method where I can have this class running, and be able to call methods from within it, even if it's calling class is shut down. The singleton class is simple. It starts a thread that loads the file into the database, while having methods to report on the current status. In a nutshell it's al little like this: public sealed class BulkFileLoader { static BulkFileLoader instance = null; int currentCount = 0; BulkFileLoader() public static BulkFileLoader Instance { // Instanciate the instance class if necessary, and return it } public void Go() { // kick of 'ProcessFile' thread } public void GetCurrentCount() { return currentCount; } private void ProcessFile() { while (more rows in the import file) { // insert the row into the database currentCount++; } } } The idea is that you can get an instance of BulkFileLoader to execute, which will process a file to load, while at any time you can get realtime updates on the number of rows its done so far using the GetCurrentCount() method. This works fine, except the calling class needs to stay open the whole time for the processing to continue. As soon as I stop the calling class, the BulkFileLoader instance is removed, and it stops processing the file. What I am after is a solution where it will continue to run independently, regardless of what happens to the calling class. I then tried another approach. I created a simple console application that kicks off the BulkFileLoader, and then wrapped it around as a process. This fixes one problem, since now when I kick off the process, the file will continue to load even if I close the class that called the process. However, now the problem I have is that cannot get updates on the current count, since if I try and get the instance of BulkFileLoader (which, as mentioned before is a singleton), it creates a new instance, rather than returning the instance that is currently in the executing process. It would appear that singletons don't extend into the scope of other processes running on the machine. In the end, I want to be able to kick off the BulkFileLoader, and at any time be able to find out how many rows it's processed. However, that is even if I close the application I used to start it. Can anyone see a solution to my problem?

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• AllowSetForegroundWindow & SetForegroundWindow: NPAPI plug-in wants to allow a desktop application with no success

  - by David Robert Jones

  Here it's what I have: a web browser plug-in written in C++ and a Windows application written in C#. They communicate through a named pipe. The plug-in instructs the C# application to open a file (suppose that the file is a .txt and it opens in Notepad). Once the C# application is given the command, it opens the file but Notepad doesn't show in the foreground, which isn't acceptable, I must open Notepad in the foreground. I modified the C# application so that it calls the SetForegroundWindow function. This time Notepad didn't open in the foreground, but the taskbar flashes. After reading the documentation for SetForegroundWindow and many articles I think that now I understand what the problem is: the C# application can't bring Notepad to the foreground because it wasn't the the foreground process, the browser was (?). After reading this: "A process that can set the foreground window can enable another process to set the foreground window by calling the AllowSetForegroundWindow function." I decided to modify the plug-in. This time the plug-in calls the AllowSetForegroundWindow function passing ASFW_ANY as a parameter (I know, ASFW_ANY could be risky, but I wanted to make sure that AllowSetForegroundWindow would do it). After I did the modification to the plug-in I tested it and it worked! (Opera 12.02). Then I tested it on Internet Explorer and it worked too. But the problem came when I tested it in Firefox and Chrome. The C# application didn't have the ability to bring Notepad to the foreground. I noticed that for those browsers the AllowSetForegroundWindow function was returning false. So I started investigating and I come to the conclusion that maybe it's because the plugin container that Firefox uses. An idea came to my mind: it worked in Opera 12.02, but they don't have a plugin container, although they did in Opera 12.00. So I downloaded Opera 12.00, I did the test and it failed, which makes me conclude that the plugin container is the culprit. The question is: how can I give to the C# application the ability to set foreground? I don't know how to continue, and I think that I tried all the legitimate ways. The AllowSetForegroundWindow & SetForegroundWindow seems to not apply here.

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• Type casting int into double C++

  - by user1705380

  I am new to programming and this might be an obvious question, though i cannot for life of me figure out why my program is not returning as a double. I am suppose to write a stocks program that takes in shares of stock, whole dollar portion of price and the fraction portion. And the fraction portion is to be inputted as two int values, and include a function definition with 3 int values.The function returns the price as a double. #include <iostream> using namespace std; int price(int, int, int); int main() { int dollars, numerator, denominator, price1, shares; char ans; do { cout<<"Enter the stock price and the number of shares.\n"; cout<<"Enter the price and integers: Dollars, numerator, denominator\n"; cin>>dollars>>numerator>>denominator; cout<<"Enter the number of shares held\n"; cin>>shares; cout<<shares; price1 = price(dollars,numerator,denominator); cout<<" shares of stock with market price of "; cout<< dollars << " " << numerator<<'/'<<denominator<<endl; cout<<"have a value of " << shares * price1<<endl; cout<<"Enter either Y/y to continue"; cin>>ans; }while (ans == 'Y' || ans == 'y'); system("pause"); return 0; } int price(int dollars, int numerator, int denominator) { return dollars + numerator/static_cast<double>(denominator); }

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• How to avoid my script to freeze

  - by jemz

  I have socket server script that continuously running listening for the GPS device that runs in PHP CLI,my problem is that my socket will freeze if it executes long time,how do I prevent this so that my script will not freeze.I have no idea on this socket.this is the first time that I use socket connection. I appreciate someone can help my problem. <?php error_reporting(-1); ini_set('display_errors', 1); set_time_limit (0); $address_server = 'xxx.xxx.xx.xx'; $port_server = xxxx; $isTrue = true; socketfunction($address_server,$port_server,$isTrue); function socketfunction($address,$port,$done){ $sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP); socket_set_option($sock, SOL_SOCKET, SO_REUSEADDR, 1); socket_bind($sock, $address, $port); socket_listen($sock); $clients = array($sock); while ($done ) { $file = fopen('txt.log','a'); $read = $clients; $write = NULL; $except = NULL; $tv_sec = 0; if (socket_select($read, $write , $except, $tv_sec) < 1){ continue; } // checking client if (in_array($sock, $read)) { $clients[] = $newsock = socket_accept($sock); $key = array_search($sock, $read); unset($read[$key]); } //handle client for reading foreach ($read as $read_sock) { $data = @socket_read($read_sock, 1024, PHP_NORMAL_READ); if ($data === false) { $key = array_search($read_sock, $clients); unset($clients[$key]); echo "client disconnected.\n"; echo "Remaining ".(count($clients) - 1)."client(s) connected\r\n"; continue; } $data = trim($data); if (!empty($data)) { echo("Returning stripped input\n"); fwrite($file,$data."\n"); } } // end of reading foreach fclose($file); }//end while socket_close($sock); } ?> Thank you in advance.

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• Python - 2 Questions: Editing a variable in a function and changing the order of if else statements

  - by Eric

  First of all, I should explain what I'm trying to do first. I'm creating a dungeon crawler-like game, and I'm trying to program the movement of computer characters/monsters in the map. The map is basically a Cartesian coordinate grid. The locations of characters are represented by tuples of the x and y values, (x,y). The game works by turns, and in a turn a character can only move up, down, left or right 1 space. I'm creating a very simple movement system where the character will simply make decisions to move on a turn by turn basis. Essentially a 'forgetful' movement system. A basic flow chart of what I'm intending to do: Find direction towards destination Make a priority list of movements to be done using the direction eg.('r','u','d','l') means it would try to move right first, then up, then down, then left. Try each of the possibilities following the priority order. If the first movement fails (blocked by obstacle etc.), then it would successively try the movements until the first one that is successful, then it would stop. At step 3, the way I'm trying to do it is like this: def move(direction,location): try: -snip- # Tries to move, raises the exception Movementerror if cannot move in the direction return 1 # Indicates movement successful except Movementerror: return 0 # Indicates movement unsuccessful (thus character has not moved yet) prioritylist = ('r','u','d','l') if move('r',location): pass elif move('u',location): pass elif move('d',location): pass elif move('l',location): pass else: pass In the if/else block, the program would try the first movement on the priority on the priority list. At the move function, the character would try to move. If the character is not blocked and does move, it returns 1, leading to the pass where it would stop. If the character is blocked, it returns 0, then it tries the next movement. However, this results in 2 problems: How do I edit a variable passed into a function inside the function itself, while returning if the edit is successful? I have been told that you can't edit a variable inside a function as it won't really change the value of the variable, it just makes the variable inside the function refer to something else while the original variable remain unchanged. So, the solution is to return the value and then assign the variable to the returned value. However, I want it to return another value indicating if this edit is successful, so I want to edit this variable inside the function itself. How do I do so? How do I change the order of the if/else statements to follow the order of the priority list? It needs to be able to change during runtime as the priority list can change resulting in a different order of movement to try.

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• nginx: problem configuring a proxy_pass

  - by Ofer Bar

  I'm converting a web app from apache to nginx. In apache's httpd.conf I have: ProxyPass /proxy/ http:// ProxyPassReverse /proxy/ http:// The idea is the client send this url: http://web-server-domain/proxy/login-server-addr/loginUrl.php?user=xxx&pass=yyy and the web server calls: http://login-server-addr/loginUrl.php?user=xxx&pass=yyy My nginx.conf is attached below and it is not working. At the moment it looks like it is calling the server, but returning an application error. This seems promising but any attempt to debug this failed! I can't trace any of the calls as nginx refuses to place them in the error file. Also, placing echo statement on the login server did not help either which is weird. The nginx documentation isn't very helpful about this. Any suggestion on how to configure a proxy_pass? Thanks! user nginx; worker_processes 1; #error_log /var/log/nginx/error.log; error_log /var/log/nginx/error.log notice; #error_log /var/log/nginx/error.log info; pid /var/run/nginx.pid; events { worker_connections 1024; } http { include /etc/nginx/mime.types; default_type application/octet-stream; log_format main '$remote_addr - $remote_user [$time_local] "$request" ' '$status $body_bytes_sent "$http_referer" ' '"$http_user_agent" "$http_x_forwarded_for"'; access_log /var/log/nginx/access.log main; sendfile on; #tcp_nopush on; #keepalive_timeout 0; keepalive_timeout 65; #gzip on; # # The default server # server { rewrite_log on; listen 80; server_name _; #charset koi8-r; #access_log logs/host.access.log main; #root /var/www/live/html; index index.php index.html index.htm; location ~ ^/proxy/(.*$) { #location /proxy/ { # rewrite ^/proxy(.*) http://$1 break; proxy_set_header X-Forwarded-Host $host; proxy_set_header X-Forwarded-Server $host; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_buffering off; proxy_pass http://$1; #proxy_pass "http://173.231.134.36/messages_2.7.0/loginUser.php?userID=ofer.fly%40gmail.com&password=y4HTD93vrshMNcy2Qr5ka7ia0xcaa389f4885f59c9"; break; } location / { root /var/www/live/html; #if ( $uri ~ ^/proxy/(.*) ) { # proxy_pass http://$1; # break; #} #try_files $uri $uri/ /index.php; } error_page 404 /404.html; #location = /404.html { # root /usr/share/nginx/html; #} # redirect server error pages to the static page /50x.html # #error_page 500 502 503 504 /50x.html; #location = /50x.html { # root /usr/share/nginx/html; #} # proxy the PHP scripts to Apache listening on 127.0.0.1:80 # #location ~ \.php$ { # proxy_pass http://127.0.0.1; #} # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000 # location ~ \.php$ { #root html; fastcgi_pass 127.0.0.1:9000; fastcgi_index index.php; #fastcgi_param SCRIPT_FILENAME /usr/share/nginx/html$fastcgi_script_name; fastcgi_param SCRIPT_FILENAME /var/www/live/html$fastcgi_script_name; include fastcgi_params; } # deny access to .htaccess files, if Apache's document root # concurs with nginx's one # #location ~ /\.ht { # deny all; #} } # Load config files from the /etc/nginx/conf.d directory include /etc/nginx/conf.d/*.conf; }

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• Can't logging in file from tomcat6 with log4j

  - by Ivan Nakov

  I have one stupid problem, which is killing me from hours. I'm trying to configure loggin to my project. I started with a simple Spring MVC project generated by STS, then added org.apache.log4j.RollingFileAppender to the existing log4j.xml file. <?xml version="1.0" encoding="UTF-8"?> <!-- Appenders --> <appender name="console" class="org.apache.log4j.ConsoleAppender"> <param name="Target" value="System.out" /> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="%-5p: %c - %m%n" /> </layout> </appender> <appender name="FilleAppender" class="org.apache.log4j.RollingFileAppender"> <param name="maxFileSize" value="100KB" /> <param name="maxBackupIndex" value="2" /> <param name="File" value="/home/ivan/Desktop/app.log" /> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="%d{ABSOLUTE} %5p %c{1}: %m%n " /> </layout> </appender> <!-- Application Loggers --> <logger name="org.elsys.logger"> <level value="debug" /> </logger> <!-- 3rdparty Loggers --> <logger name="org.springframework.core"> <level value="info" /> </logger> <logger name="org.springframework.beans"> <level value="info" /> </logger> <logger name="org.springframework.context"> <level value="info" /> </logger> <logger name="org.springframework.web"> <level value="info" /> </logger> <!-- Root Logger --> <root> <priority value="debug" /> <appender-ref ref="FilleAppender" /> </root> When I deploy project to tomcat6 server and open the url, logger doesn't generate log file. I'm trying to log from this controller: @Controller public class HomeController { private static final Logger logger = LoggerFactory.getLogger(HomeController.class); /** * Simply selects the home view to render by returning its name. */ @RequestMapping(value = "/", method = RequestMethod.GET) public String home(Locale locale, Model model) { logger.info("Welcome home! the client locale is "+ locale.toString()); Date date = new Date(); DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.LONG, locale); String formattedDate = dateFormat.format(date); logger.debug("send view"); model.addAttribute("serverTime", formattedDate ); return "home"; } } When I log from this simple Main.class, it works correct. public class Main { public static void main(String[] args) { Logger log = LoggerFactory.getLogger(Main.class); log.debug("Test"); } } I'm using tomcat6 and Ubuntu 11.10. I made a research in net and i found various options to fix this problem, but they don't help me. Please if someone have ideas how to fix it, help me.

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• Custom SNMP Cacti Data Source fails to update

  - by Andrew Wilkinson

  I'm trying to create a custom SNMP datasource for Cacti but despite everything I can check being correct, it is not creating the rrd file, or updating it even when I create it. Other, standard SNMP sources are working correctly so it's not SNMP or permissions that are the problem. I've created a new Data Query, which when I click on "Verbose Query" on the device screen returns the following: + Running data query [10]. + Found type = '3' [SNMP Query]. + Found data query XML file at '/volume1/web/cacti/resource/snmp_queries/syno_volume_stats.xml' + XML file parsed ok. + missing in XML file, 'Index Count Changed' emulated by counting oid_index entries + Executing SNMP walk for list of indexes @ '.1.3.6.1.2.1.25.2.3.1.3' Index Count: 8 + Index found at OID: '.1.3.6.1.2.1.25.2.3.1.3.1' value: 'Physical memory' + Index found at OID: '.1.3.6.1.2.1.25.2.3.1.3.3' value: 'Virtual memory' + Index found at OID: '.1.3.6.1.2.1.25.2.3.1.3.6' value: 'Memory buffers' + Index found at OID: '.1.3.6.1.2.1.25.2.3.1.3.7' value: 'Cached memory' + Index found at OID: '.1.3.6.1.2.1.25.2.3.1.3.10' value: 'Swap space' + Index found at OID: '.1.3.6.1.2.1.25.2.3.1.3.31' value: '/' + Index found at OID: '.1.3.6.1.2.1.25.2.3.1.3.32' value: '/volume1' + Index found at OID: '.1.3.6.1.2.1.25.2.3.1.3.33' value: '/opt' + index_parse at OID: '.1.3.6.1.2.1.25.2.3.1.3.1' results: '1' + index_parse at OID: '.1.3.6.1.2.1.25.2.3.1.3.3' results: '3' + index_parse at OID: '.1.3.6.1.2.1.25.2.3.1.3.6' results: '6' + index_parse at OID: '.1.3.6.1.2.1.25.2.3.1.3.7' results: '7' + index_parse at OID: '.1.3.6.1.2.1.25.2.3.1.3.10' results: '10' + index_parse at OID: '.1.3.6.1.2.1.25.2.3.1.3.31' results: '31' + index_parse at OID: '.1.3.6.1.2.1.25.2.3.1.3.32' results: '32' + index_parse at OID: '.1.3.6.1.2.1.25.2.3.1.3.33' results: '33' + Located input field 'index' [walk] + Executing SNMP walk for data @ '.1.3.6.1.2.1.25.2.3.1.3' + Found item [index='Physical memory'] index: 1 [from value] + Found item [index='Virtual memory'] index: 3 [from value] + Found item [index='Memory buffers'] index: 6 [from value] + Found item [index='Cached memory'] index: 7 [from value] + Found item [index='Swap space'] index: 10 [from value] + Found item [index='/'] index: 31 [from value] + Found item [index='/volume1'] index: 32 [from value] + Found item [index='/opt'] index: 33 [from value] + Located input field 'volsizeunit' [walk] + Executing SNMP walk for data @ '.1.3.6.1.2.1.25.2.3.1.4' + Found item [volsizeunit='1024 Bytes'] index: 1 [from value] + Found item [volsizeunit='1024 Bytes'] index: 3 [from value] + Found item [volsizeunit='1024 Bytes'] index: 6 [from value] + Found item [volsizeunit='1024 Bytes'] index: 7 [from value] + Found item [volsizeunit='1024 Bytes'] index: 10 [from value] + Found item [volsizeunit='4096 Bytes'] index: 31 [from value] + Found item [volsizeunit='4096 Bytes'] index: 32 [from value] + Found item [volsizeunit='4096 Bytes'] index: 33 [from value] + Located input field 'volsize' [walk] + Executing SNMP walk for data @ '.1.3.6.1.2.1.25.2.3.1.5' + Found item [volsize='1034712'] index: 1 [from value] + Found item [volsize='3131792'] index: 3 [from value] + Found item [volsize='1034712'] index: 6 [from value] + Found item [volsize='775904'] index: 7 [from value] + Found item [volsize='2097080'] index: 10 [from value] + Found item [volsize='612766'] index: 31 [from value] + Found item [volsize='1439812394'] index: 32 [from value] + Found item [volsize='1439812394'] index: 33 [from value] + Located input field 'volused' [walk] + Executing SNMP walk for data @ '.1.3.6.1.2.1.25.2.3.1.6' + Found item [volused='1022520'] index: 1 [from value] + Found item [volused='1024096'] index: 3 [from value] + Found item [volused='32408'] index: 6 [from value] + Found item [volused='775904'] index: 7 [from value] + Found item [volused='1576'] index: 10 [from value] + Found item [volused='148070'] index: 31 [from value] + Found item [volused='682377865'] index: 32 [from value] + Found item [volused='682377865'] index: 33 [from value] AS you can see it appears to be returning the correct data. I've also set up data templates and graph templates to display the data. The create graphs for a device screen shows the correct data, and when selecting one row can clicking create a new data source and graph are created. Unfortunately the data source is never updated. Increasing the poller log level shows that it appears to not even be querying the data source, despite it being used? What should my next steps to debug this issue be?

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• Intermittent 404 on select assets, LAMP stack

  - by Tom Lagier

  We have a LAMP stack WordPress server that is serving most assets correctly. However, one plugin's CSS file and several images are returning soft 404s roughly 20% of the time. I can't find any reference to the 404 in the access logs, but the browser is definitely receiving a 404 response from somewhere (WordPress, I would assume). When I use an alias URL that does not match the site URL but does resolve to the asset path, the resource loads correctly 100% of the time. However, using the site url only resolves for the select, problematic assets 20% of the time. You can test one of the problematic assets here: http://www.mreco.org/wp-content/uploads/2014/05/zero-cost.jpg However the alias link always resolves correctly: http://mr-eco.wordpress.promocampaigns.com/wp-content/uploads/2014/05/zero-cost.jpg Stranger, if I attempt to access outdated content that definitely does not exist on the server, at the live URL it returns the content roughly 50% of the time. Using the alias link, it 404s 100% of the time - the correct behavior. Error log and PHP error log are clean. A sample access log (pulled from grep 'zero-cost.jpg' /var/log/httpd/mr-eco-access_log) from several refreshes of the live direct link (where I am not seeing any 404's): 10.166.202.202 - - [28/May/2014:20:27:41 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.166.202.202 - - [28/May/2014:20:27:42 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.166.202.202 - - [28/May/2014:20:27:43 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.166.202.202 - - [28/May/2014:20:27:43 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.176.201.37 - - [28/May/2014:20:27:56 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 200 57027 Chrome's dev tools list the following network activity before displaying 404 page content: zero-cost.jpg /wp-content/uploads/2014/05 GET 404 Not Found text/html Other 15.9?KB 73.2?KB 953?ms 947?ms My Apache configuration is standard, I've listed the virtual host entry and .htaccess file below. I can provide other parts of Apache config if necessary. Virtual host: <VirtualHost *:80> DocumentRoot /var/www/public_html/mr-eco.wordpress.promocampaigns.com ServerName www.mreco.org ServerAlias mreco.org mr-eco.wordpress.promocampaigns.com ErrorLog logs/mr-eco-error_log CustomLog logs/mr-eco-access_log common <Directory /var/www/public_html/mr-eco.wordpress.promocampaigns.com> AllowOverride All SetOutputFilter DEFLATE </Directory> </VirtualHost> .htaccess: # BEGIN WordPress <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L] </IfModule> # END WordPress I have checked for multiple A records and can confirm that there is a single A record pointing at the domain: ;; ANSWER SECTION: mreco.org. 60 IN A 50.18.58.174 I'm fairly new to systems administration, and at a complete loss as to what could cause this. In the past, inconsistently 404ing assets have been because of out-of-sync instances behind a load balancer. In this case, it is a single instance behind the load balancer. Because of the inconsistency, it feels like a caching issue. We don't make use of Apache caching, and as far as I know WordPress should not be caching either. What I've done so far: Reset WordPress permalinks Disabled WordPress plugins Re-generated WordPress .htaccess file Swapped ServerName and ServerAlias directives Cleared browser cache Confirmed disk location of resources Checked PHP, access, and error logs Confirmed correct DNS setup (can post if necessary) I'm at a total loss. Thanks for helping me out!

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• Openldap/Sasl/GSSAPI on Debian: Key table entry not found

  - by badbishop

  The goal: to make an OpenLDAP server to authenticate using Kerberos V via GSSAPI Setup: several virtual machines running on freshly installed/updated Debian Squeeze A master KDC server kdc.example.com A LDAP server, running OpenLDAP ldap.example.com The problem: tom@ldap:~$ ldapsearch -b 'dc=example,dc=com' SASL/GSSAPI authentication started ldap_sasl_interactive_bind_s: Other (e.g., implementation specific) error (80) additional info: SASL(-1): generic failure: GSSAPI Error: Unspecified GSS failure. Minor code may provide more information (Key table entry not found) One might suggest to add that bloody keytab entry, but here's the real problem: ktutil: rkt /etc/ldap/ldap.keytab ktutil: list slot KVNO Principal ---- ---- --------------------------------------------------------------------- 1 2 ldap/[email protected] 2 2 ldap/[email protected] 3 2 ldap/[email protected] 4 2 ldap/[email protected] So, the entry as suggested by the OpenLDAP manual is there allright. Deleting and re-creating both service principal and the keytab on ldap.example.com didn't help, I get the same error. And before I make the keytab file readable by openldap, I get "Permission denied" error instead of the one in the subject. Which implies, that the right keytab file is being accessed, as set in /etc/default/slapd. I have my doubts about the following part of slapd config: root@ldap:~# cat /etc/ldap/slapd.d/cn\=config.ldif | grep -v "^#" dn: cn=config objectClass: olcGlobal cn: config olcArgsFile: /var/run/slapd/slapd.args olcLogLevel: 256 olcPidFile: /var/run/slapd/slapd.pid olcToolThreads: 1 structuralObjectClass: olcGlobal entryUUID: d6737f5c-d321-1030-9dbe-27d2a7751e11 olcSaslHost: kdc.example.com olcSaslRealm: EXAMPLE.COM olcSaslSecProps: noplain,noactive,noanonymous,minssf=56 olcAuthzRegexp: {0}"uid=([^/]*),cn=EXAMPLE.COM,cn=GSSAPI,cn=auth" "uid=$1,ou=People,dc=example,dc=com" olcAuthzRegexp: {1}"uid=host/([^/]*).example.com,cn=example.com,cn=gssapi,cn=auth" "cn=$1,ou=hosts,dc=example,dc=com" A HOWTO at https://help.ubuntu.com/community/OpenLDAPServer#Kerberos_Authentication mentiones vaguely: Also, it is frequently necessary to map the Distinguished Name (DN) of an authorized Kerberos client to an existing entry in the DIT. I fail to understand where in the tree this should be defined, what schema should be used, etc. After hours of googling, it's official: I'm stuck! Please, help. Other things checked: Kerberos as such works fine (I can ssh without using a password to any machine in this setup). That means there should be no DNS-related problems. ldapsearch -b 'dc=example,dc=com' -x works OK. SASL/GSSAPI has been tested using sasl-sample-server -m GSSAPI -s ldap and sasl-sample-client -s ldap -n ldap.example.com -u tom without errors: root@ldap:~# sasl-sample-server -m GSSAPI -s ldap Forcing use of mechanism GSSAPI Sending list of 1 mechanism(s) S: R1NTQVBJ Waiting for client mechanism... C: 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 'GSSAPI' Sending response... S: YIGZBgkqhkiG9xIBAgICAG+BiTCBhqADAgEFoQMCAQ+iejB4oAMCARKicQRvkxggi9pW+yJ1ExbTwLDclqw/VQ98aPq8mt39hkO6PPfcO2cB+t6vJ01xRKBrT9D2qF2XK0SWD4PQNb5UFbH4RM/bKAxDuCfZ1MHKgIWTLu4bK7VGZTbYydcckU2d910jIdvkkHhaRqUEM4cqp/cR Waiting for client reply... C: got '' Sending response... S: BQQF/wAMAAAAAAAAMBOWqQcACAAlCodrXW66ZObsEd4= Waiting for client reply... C: BQQE/wAMAAAAAAAAFUYbXQQACAB0b20VynB4uGH/iIzoRhw=got '?' Negotiation complete Username: tom Realm: (NULL) SSF: 56 sending encrypted message 'srv message 1' S: AAAASgUEB/8AAAAAAAAAADATlqrqrBW0NRfPMXMdMz+zqY32YakrHqFps3o/vO6yDeyPSaSqprrhI+t7owk7iOsbrZ/idJRxCBm8Wazx Waiting for encrypted message... C: AAAATQUEBv8AAAAAAAAAABVGG17WC1+/kIV9xTMUdq6Y4qYmmTahHVCjidgGchTOOOrBLEwA9IqiTCdRFPVbK1EgJ34P/vxMQpV1v4WZpcztgot '' recieved decoded message 'client message 1' root@ldap:~# sasl-sample-client -s ldap -n ldap.example.com -u tom service=ldap Waiting for mechanism list from server... S: R1NTQVBJrecieved 6 byte message Choosing best mechanism from: GSSAPI returning OK: tom Using mechanism GSSAPI Preparing initial. Sending initial response... C: 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 Waiting for server reply... S: YIGZBgkqhkiG9xIBAgICAG+BiTCBhqADAgEFoQMCAQ+iejB4oAMCARKicQRvkxggi9pW+yJ1ExbTwLDclqw/VQ98aPq8mt39hkO6PPfcO2cB+t6vJ01xRKBrT9D2qF2XK0SWD4PQNb5UFbH4RM/bKAxDuCfZ1MHKgIWTLu4bK7VGZTbYydcckU2d910jIdvkkHhaRqUEM4cqp/cRrecieved 156 byte message C: Waiting for server reply... S: BQQF/wAMAAAAAAAAMBOWqQcACAAlCodrXW66ZObsEd4=recieved 32 byte message Sending response... C: BQQE/wAMAAAAAAAAFUYbXQQACAB0b20VynB4uGH/iIzoRhw= Negotiation complete Username: tom SSF: 56 Waiting for encoded message... S: AAAASgUEB/8AAAAAAAAAADATlqrqrBW0NRfPMXMdMz+zqY32YakrHqFps3o/vO6yDeyPSaSqprrhI+t7owk7iOsbrZ/idJRxCBm8Wazxrecieved 78 byte message recieved decoded message 'srv message 1' sending encrypted message 'client message 1' C: AAAATQUEBv8AAAAAAAAAABVGG17WC1+/kIV9xTMUdq6Y4qYmmTahHVCjidgGchTOOOrBLEwA9IqiTCdRFPVbK1EgJ34P/vxMQpV1v4WZpczt

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• Rewriting Apache URLs to use only paths and set response headers

  - by jabley

  I have apache httpd in front of an application running in Tomcat. The application exposes URLs of the form: /path/to/images?id={an-image-id} The entities returned by such URLs are images (even though URIs are opaque, I find human-friendly ones are easier to work with!). The application does not set caching directives on the image response, so I've added that via Apache. # LocationMatch to set caching directives on image responses <LocationMatch "^/path/to/images$"> # Can't have Set-Cookie on response, otherwise the downstream caching proxy # won't cache! Header unset Set-Cookie # Mark the response as cacheable. Header append Cache-Control "max-age=8640000" </LocationMatch> Note that I can't use ExpiresByType since not all images served by the app have versioned URIs. I know that ones served by the /path/to/images resource handler are versioned URIs though, which don't perform any sort of content negotiation, and thus are ripe for Far Future Expires management. This is working well for us. Now a requirement has come up to put something else in front of the app (in this case, Amazon CloudFront) to further distribute and cache some of the content. Amazon CloudFront will not pass query string parameters through to my origin server. I thought I would be able to work around this, by changing my apache config appropriately: # Rewrite to map new Amazon CloudFront friendly URIs to the application resources RewriteRule ^/new/path/to/images/([0-9]+) /path/to/images?id=$1 [PT] # LocationMatch to set caching directives on image responses <LocationMatch "^/path/to/images$"> # Can't have Set-Cookie on response, otherwise the downstream caching proxy # won't cache! Header unset Set-Cookie # Mark the response as cacheable. Header append Cache-Control "max-age=8640000" </LocationMatch> This works fine in terms of serving the content, but there are no longer caching directives with the response. I've tried playing around with [PT], [P] for the RewriteRule, and adding a new LocationMatch directive: # Rewrite to map new Amazon CloudFront friendly URIs to the application resources # /new/path/to/images/12345 -> /path/to/images?id=12345 RewriteRule ^/new/path/to/images/([0-9]+) /path/to/images?id=$1 [PT] # LocationMatch to set caching directives on image responses <LocationMatch "^/path/to/images$"> # Can't have Set-Cookie on response, otherwise the downstream caching proxy # won't cache! Header unset Set-Cookie # Mark the response as cacheable. Header append Cache-Control "max-age=8640000" </LocationMatch> <LocationMatch "^/new/path/to/images/"> # Can't have Set-Cookie on response, otherwise the downstream caching proxy # won't cache! Header unset Set-Cookie # Mark the response as cacheable. Header append Cache-Control "max-age=8640000" </LocationMatch> Unfortunately, I'm still unable to get the Cache-Control header added to the response with the new URL format. Please point out what I'm missing to get /new/path/to/images/12345 returning a 200 response with a Cache-Control: max-age=8640000 header. Pointers as to how to debug apache like this would be appreciated as well!

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• DropDownList and SelectListItem Array Item Updates in MVC

  - by Rick Strahl

  So I ran into an interesting behavior today as I deployed my first MVC 4 app tonight. I have a list form that has a filter drop down that allows selection of categories. This list is static and rarely changes so rather than loading these items from the database each time I load the items once and then cache the actual SelectListItem[] array in a static property. However, when we put the site online tonight we immediately noticed that the drop down list was coming up with pre-set values that randomly changed. Didn't take me long to trace this back to the cached list of SelectListItem[]. Clearly the list was getting updated - apparently through the model binding process in the selection postback. To clarify the scenario here's the drop down list definition in the Razor View:@Html.DropDownListFor(mod => mod.QueryParameters.Category, Model.CategoryList, "All Categories") where Model.CategoryList gets set with:[HttpPost] [CompressContent] public ActionResult List(MessageListViewModel model) { InitializeViewModel(model); busEntry entryBus = new busEntry(); var entries = entryBus.GetEntryList(model.QueryParameters); model.Entries = entries; model.DisplayMode = ApplicationDisplayModes.Standard; model.CategoryList = AppUtils.GetCachedCategoryList(); return View(model); } The AppUtils.GetCachedCategoryList() method gets the cached list or loads the list on the first access. The code to load up the list is housed in a Web utility class. The method looks like this:/// <summary> /// Returns a static category list that is cached /// </summary> /// <returns></returns> public static SelectListItem[] GetCachedCategoryList() { if (_CategoryList != null) return _CategoryList; lock (_SyncLock) { if (_CategoryList != null) return _CategoryList; var catBus = new busCategory(); var categories = catBus.GetCategories().ToList(); // Turn list into a SelectItem list var catList= categories .Select(cat => new SelectListItem() { Text = cat.Name, Value = cat.Id.ToString() }) .ToList(); catList.Insert(0, new SelectListItem() { Value = ((int)SpecialCategories.AllCategoriesButRealEstate).ToString(), Text = "All Categories except Real Estate" }); catList.Insert(1, new SelectListItem() { Value = "-1", Text = "--------------------------------" }); _CategoryList = catList.ToArray(); } return _CategoryList; } private static SelectListItem[] _CategoryList ; This seemed normal enough to me - I've been doing stuff like this forever caching smallish lists in memory to avoid an extra trip to the database. This list is used in various places throughout the application - for the list display and also when adding new items and setting up for notifications etc.. Watch that ModelBinder! However, it turns out that this code is clearly causing a problem. It appears that the model binder on the [HttpPost] method is actually updating the list that's bound to and changing the actual entry item in the list and setting its selected value. If you look at the code above I'm not setting the SelectListItem.Selected value anywhere - the only place this value can get set is through ModelBinding. Sure enough when stepping through the code I see that when an item is selected the actual model - model.CategoryList[x].Selected - reflects that. This is bad on several levels: First it's obviously affecting the application behavior - nobody wants to see their drop down list values jump all over the place randomly. But it's also a problem because the array is getting updated by multiple ASP.NET threads which likely would lead to odd crashes from time to time. Not good! In retrospect the modelbinding behavior makes perfect sense. The actual items and the Selected property is the ModelBinder's way of keeping track of one or more selected values. So while I assumed the list to be read-only, the ModelBinder is actually updating it on a post back producing the rather surprising results. Totally missed this during testing and is another one of those little - "Did you know?" moments. So, is there a way around this? Yes but it's maybe not quite obvious. I can't change the behavior of the ModelBinder, but I can certainly change the way that the list is generated. Rather than returning the cached list, I can return a brand new cloned list from the cached items like this:/// <summary> /// Returns a static category list that is cached /// </summary> /// <returns></returns> public static SelectListItem[] GetCachedCategoryList() { if (_CategoryList != null) { // Have to create new instances via projection // to avoid ModelBinding updates to affect this // globally return _CategoryList .Select(cat => new SelectListItem() { Value = cat.Value, Text = cat.Text }) .ToArray(); } …}  The key is that newly created instances of SelectListItems are returned not just filtered instances of the original list. The key here is 'new instances' so that the ModelBinding updates do not update the actual static instance. The code above uses LINQ and a projection into new SelectListItem instances to create this array of fresh instances. And this code works correctly - no more cross-talk between users. Unfortunately this code is also less efficient - it has to reselect the items and uses extra memory for the new array. Knowing what I know now I probably would have not cached the list and just take the hit to read from the database. If there is even a possibility of thread clashes I'm very wary of creating code like this. But since the method already exists and handles this load in one place this fix was easy enough to put in. Live and learn. It's little things like this that can cause some interesting head scratchers sometimes…© Rick Strahl, West Wind Technologies, 2005-2012Posted in MVC  ASP.NET  .NET   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• MvcExtensions – Bootstrapping

  - by kazimanzurrashid

  When you create a new ASP.NET MVC application you will find that the global.asax contains the following lines: namespace MvcApplication1 { // Note: For instructions on enabling IIS6 or IIS7 classic mode, // visit http://go.microsoft.com/?LinkId=9394801 public class MvcApplication : System.Web.HttpApplication { public static void RegisterRoutes(RouteCollection routes) { routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.MapRoute( "Default", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults ); } protected void Application_Start() { AreaRegistration.RegisterAllAreas(); RegisterRoutes(RouteTable.Routes); } } } As the application grows, there are quite a lot of plumbing code gets into the global.asax which quickly becomes a design smell. Lets take a quick look at the code of one of the open source project that I recently visited: public static void RegisterRoutes(RouteCollection routes) { routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.MapRoute("Default","{controller}/{action}/{id}", new { controller = "Home", action = "Index", id = "" }); } protected override void OnApplicationStarted() { Error += OnError; EndRequest += OnEndRequest; var settings = new SparkSettings() .AddNamespace("System") .AddNamespace("System.Collections.Generic") .AddNamespace("System.Web.Mvc") .AddNamespace("System.Web.Mvc.Html") .AddNamespace("MvcContrib.FluentHtml") .AddNamespace("********") .AddNamespace("********.Web") .SetPageBaseType("ApplicationViewPage") .SetAutomaticEncoding(true); #if DEBUG settings.SetDebug(true); #endif var viewFactory = new SparkViewFactory(settings); ViewEngines.Engines.Add(viewFactory); #if !DEBUG PrecompileViews(viewFactory); #endif RegisterAllControllersIn("********.Web"); log4net.Config.XmlConfigurator.Configure(); RegisterRoutes(RouteTable.Routes); Factory.Load(new Components.WebDependencies()); ModelBinders.Binders.DefaultBinder = new Binders.GenericBinderResolver(Factory.TryGet<IModelBinder>); ValidatorConfiguration.Initialize("********"); HtmlValidationExtensions.Initialize(ValidatorConfiguration.Rules); } private void OnEndRequest(object sender, System.EventArgs e) { if (((HttpApplication)sender).Context.Handler is MvcHandler) { CreateKernel().Get<ISessionSource>().Close(); } } private void OnError(object sender, System.EventArgs e) { CreateKernel().Get<ISessionSource>().Close(); } protected override IKernel CreateKernel() { return Factory.Kernel; } private static void PrecompileViews(SparkViewFactory viewFactory) { var batch = new SparkBatchDescriptor(); batch.For<HomeController>().For<ManageController>(); viewFactory.Precompile(batch); } As you can see there are quite a few of things going on in the above code, Registering the ViewEngine, Compiling the Views, Registering the Routes/Controllers/Model Binders, Settings up Logger, Validations and as you can imagine the more it becomes complex the more things will get added in the application start. One of the goal of the MVCExtensions is to reduce the above design smell. Instead of writing all the plumbing code in the application start, it contains BootstrapperTask to register individual services. Out of the box, it contains BootstrapperTask to register Controllers, Controller Factory, Action Invoker, Action Filters, Model Binders, Model Metadata/Validation Providers, ValueProvideraFactory, ViewEngines etc and it is intelligent enough to automatically detect the above types and register into the ASP.NET MVC Framework. Other than the built-in tasks you can create your own custom task which will be automatically executed when the application starts. When the BootstrapperTasks are in action you will find the global.asax pretty much clean like the following: public class MvcApplication : UnityMvcApplication { public void ErrorLog_Filtering(object sender, ExceptionFilterEventArgs e) { Check.Argument.IsNotNull(e, "e"); HttpException exception = e.Exception.GetBaseException() as HttpException; if ((exception != null) && (exception.GetHttpCode() == (int)HttpStatusCode.NotFound)) { e.Dismiss(); } } } The above code is taken from my another open source project Shrinkr, as you can see the global.asax is longer cluttered with any plumbing code. One special thing you have noticed that it is inherited from the UnityMvcApplication rather than regular HttpApplication. There are separate version of this class for each IoC Container like NinjectMvcApplication, StructureMapMvcApplication etc. Other than executing the built-in tasks, the Shrinkr also has few custom tasks which gets executed when the application starts. For example, when the application starts, we want to ensure that the default users (which is specified in the web.config) are created. The following is the custom task that is used to create those default users: public class CreateDefaultUsers : BootstrapperTask { protected override TaskContinuation ExecuteCore(IServiceLocator serviceLocator) { IUserRepository userRepository = serviceLocator.GetInstance<IUserRepository>(); IUnitOfWork unitOfWork = serviceLocator.GetInstance<IUnitOfWork>(); IEnumerable<User> users = serviceLocator.GetInstance<Settings>().DefaultUsers; bool shouldCommit = false; foreach (User user in users) { if (userRepository.GetByName(user.Name) == null) { user.AllowApiAccess(ApiSetting.InfiniteLimit); userRepository.Add(user); shouldCommit = true; } } if (shouldCommit) { unitOfWork.Commit(); } return TaskContinuation.Continue; } } There are several other Tasks in the Shrinkr that we are also using which you will find in that project. To create a custom bootstrapping task you have create a new class which either implements the IBootstrapperTask interface or inherits from the abstract BootstrapperTask class, I would recommend to start with the BootstrapperTask as it already has the required code that you have to write in case if you choose the IBootstrapperTask interface. As you can see in the above code we are overriding the ExecuteCore to create the default users, the MVCExtensions is responsible for populating the  ServiceLocator prior calling this method and in this method we are using the service locator to get the dependencies that are required to create the users (I will cover the custom dependencies registration in the next post). Once the users are created, we are returning a special enum, TaskContinuation as the return value, the TaskContinuation can have three values Continue (default), Skip and Break. The reason behind of having this enum is, in some  special cases you might want to skip the next task in the chain or break the complete chain depending upon the currently running task, in those cases you will use the other two values instead of the Continue. The last thing I want to cover in the bootstrapping task is the Order. By default all the built-in tasks as well as newly created task order is set to the DefaultOrder(a static property), in some special cases you might want to execute it before/after all the other tasks, in those cases you will assign the Order in the Task constructor. For Example, in Shrinkr, we want to run few background services when the all the tasks are executed, so we assigned the order as DefaultOrder + 1. Here is the code of that Task: public class ConfigureBackgroundServices : BootstrapperTask { private IEnumerable<IBackgroundService> backgroundServices; public ConfigureBackgroundServices() { Order = DefaultOrder + 1; } protected override TaskContinuation ExecuteCore(IServiceLocator serviceLocator) { backgroundServices = serviceLocator.GetAllInstances<IBackgroundService>().ToList(); backgroundServices.Each(service => service.Start()); return TaskContinuation.Continue; } protected override void DisposeCore() { backgroundServices.Each(service => service.Stop()); } } That’s it for today, in the next post I will cover the custom service registration, so stay tuned.

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• Thursday Community Keynote: "By the Community, For the Community"

  - by Janice J. Heiss

  Sharat Chander, JavaOne Community Chairperson, began Thursday's Community Keynote. As part of the morning’s theme of "By the Community, For the Community," Chander noted that 60% of the material at the 2012 JavaOne conference was presented by Java Community members. "So next year, when the call for papers starts, put-in your submissions," he urged.From there, Gary Frost, Principal Member of Technical Staff, AMD, expanded upon Sunday's Strategy Keynote exploration of Project Sumatra, an OpenJDK project targeted at bringing Java to heterogeneous computing platforms (which combine the CPU and the parallel processor of the GPU into a single piece of silicon). Sumatra entails enhancing the JVM to make maximum use of these advanced platforms. Within this development space, AMD created the Aparapi API, which converts Java bytecode into OpenCL for execution on such GPU devices. The Aparapi API was open sourced in September 2011.Whether it was zooming-in on a Mandelbrot set, "the game of life," or a swarm of 10,000 Dukes in a space-bound gravitational dance, Frost's demos, using an Aparapi/OpenCL implementation, produced stunningly faster display results. He indicated that the Java 9 timeframe is where they see Project Sumatra coming to ultimate fruition, employing the Lamdas of Java 8.Returning to the theme of the keynote, Donald Smith, Director, Java Product Management, Oracle, explored a mind map graphic demonstrating the importance of Community in terms of fostering innovation. "It's the sharing and mixing of culture, the diversity, and the rapid prototyping," he said. Within this topic, Smith, brought up a panel of representatives from Cloudera, Eclipse, Eucalyptus, Perrone Robotics, and Twitter--ideal manifestations of community and innovation in the world of Java.Marten Mickos, CEO, Eucalyptus Systems, explored his company's open source cloud software platform, written in Java, and used by gaming companies, technology companies, media companies, and more. Chris Aniszczyk, Operations Engineering,Twitter, noted the importance of the JVM in terms of their multiple-language development environment. Mike Olson, CEO, Cloudera, described his company's Apache Hadoop-based software, support, and training. Mike Milinkovich, Executive Director, Eclipse Foundation, noted that they have about 270 tools projects at Eclipse, with 267 of them written in Java. Milinkovich added that Eclipse will even be going into space in 2013, as part of the control software on various experiments aboard the International Space Station. Lastly, Paul Perrone, CEO, Perrone Robotics, detailed his company's robotics and automation software platform built 100% on Java, including Java SE and Java ME--"on rat, to cat, to elephant-sized systems." Milinkovic noted that communities are by nature so good at innovation because of their very openness--"The more open you make your innovation process, the more ideas are challenged, and the more developers are focused on justifying their choices all the way through the process."From there, Georges Saab, VP Development Java SE OpenJDK, continued the topic of innovation and helping the Java Community to "Make the Future Java." Martijn Verburg, representing the London Java Community (winner of a Duke's Choice Award 2012 for their activity in OpenJDK and JCP), soon joined Saab onstage. Verburg detailed the LJC's "Adopt a JSR" program--"to get day-to-day developers more involved in the innovation that's happening around them."  From its London launching pad, the innovative program has spread to Brazil, Morocco, Latvia, India, and more.Other active participants in the program joined Verburg onstage--Ben Evans, London Java Community; James Gough, Stackthread; Bruno Souza, SOUJava; Richard Warburton, jClarity; and Cecelia Borg, Oracle--OpenJDK Onboarding. Together, the group explored the goals and tasks inherent in the Adopt a JSR program--from organizing hack days (testing prototype implementations), to managing mailing lists and forums, to triaging issues, to evangelism—all with the goal of fostering greater community/developer involvement, but equally importantly, building better open standards. “Come join us, and make your ecosystem better!" urged Verburg.Paul Perrone returned to profile the latest in his company's robotics work around Java--including the AARDBOTS family of smaller robotic vehicles, running the Perrone MAX platform on top of the Java JVM. Perrone took his "Rumbles" four-wheeled robot out for a spin onstage--a roaming, ARM-based security-bot vehicle, complete with IR, ultrasonic, and "cliff" sensors (the latter, for the raised stage at JavaOne). As an ultimate window into the future of robotics, Perrone displayed a "head-set" controller--a sensor directed at the forehead to monitor brainwaves, for the someday-implementation of brain-to-robot control.Then, just when it seemed this might be the end of the day's futuristic offerings, a mystery voice from offstage pronounced "I've got some toys"--proving to be guest-visitor James Gosling, there to explore his cutting-edge work with Liquid Robotics. While most think of robots as something with wheels or arms or lasers, Gosling explained, the Liquid Robotics vehicle is an entirely new and innovative ocean-going 'bot. Looking like a floating surfboard, with an attached set of underwater wings, the autonomous devices roam the oceans using only the energy of ocean waves to propel them, and a single actuated rudder to steer. "We have to accomplish all guidance just by wiggling the rudder," Gosling said. The devices offer applications from self-installing weather buoy, to pollution monitoring station, to marine mammal monitoring device, to climate change data gathering, to even ocean life genomic sampling. The early versions of the vehicle used C code on very tiny industrial micro controllers, where they had to "count the bytes one at a time."  But the latest generation vehicles, which just hit the water a week or so ago, employ an ARM processor running Linux and the ARM version of JDK 7. Gosling explained that vehicle communication from remote locations is achieved via the Iridium satellite network. But because of the costs of this communication path, the data must be sent in very small bursts--using SBD short burst data. "It costs $1/kb, so that rules everything in the software design,” said Gosling. “If you were trying to stream a Netflix video over this, it would cost a million dollars a movie. …We don't have a 'big data' problem," he quipped. There are currently about 150 Liquid Robotics vehicles out traversing the oceans. Gosling demonstrated real time satellite tracking of several vehicles currently at sea, noting that Java is actually particularly good at AI applications--due to the language having garbage collection, which facilitates complex data structures. To close-out his time onstage, Gosling of course participated in the ceremonial Java tee-shirt toss out to the audience…In parting, Chander passed the JavaOne Community Chairperson baton to Stephen Chin, Java Technology Evangelist, Oracle. Onstage in full motorcycle gear, Chin noted that he'll soon be touring Europe by motorcycle, meeting Java Community Members and streaming live via UStream--the ultimate manifestation of community and technology!  He also reminded attendees of the upcoming JavaOne Latin America 2012, São Paulo, Brazil (December 4-6, 2012), and stated that the CFP (call for papers) at the conference has been extended for one more week. "Remember, December is summer in Brazil!" Chin said.

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• Listing common SQL Code Smells.

  - by Phil Factor

  Once you’ve done a number of SQL Code-reviews, you’ll know those signs in the code that all might not be well. These ’Code Smells’ are coding styles that don’t directly cause a bug, but are indicators that all is not well with the code. . Kent Beck and Massimo Arnoldi seem to have coined the phrase in the "OnceAndOnlyOnce" page of www.C2.com, where Kent also said that code "wants to be simple". Bad Smells in Code was an essay by Kent Beck and Martin Fowler, published as Chapter 3 of the book ‘Refactoring: Improving the Design of Existing Code’ (ISBN 978-0201485677) Although there are generic code-smells, SQL has its own particular coding habits that will alert the programmer to the need to re-factor what has been written. See Exploring Smelly Code   and Code Deodorants for Code Smells by Nick Harrison for a grounding in Code Smells in C# I’ve always been tempted by the idea of automating a preliminary code-review for SQL. It would be so useful to trawl through code and pick up the various problems, much like the classic ‘Lint’ did for C, and how the Code Metrics plug-in for .NET Reflector by Jonathan 'Peli' de Halleux is used for finding Code Smells in .NET code. The problem is that few of the standard procedural code smells are relevant to SQL, and we need an agreed list of code smells. Merrilll Aldrich made a grand start last year in his blog Top 10 T-SQL Code Smells.However, I'd like to make a start by discovering if there is a general opinion amongst Database developers what the most important SQL Smells are. One can be a bit defensive about code smells. I will cheerfully write very long stored procedures, even though they are frowned on. I’ll use dynamic SQL occasionally. You can only use them as an aid for your own judgment and it is fine to ‘sign them off’ as being appropriate in particular circumstances. Also, whole classes of ‘code smells’ may be irrelevant for a particular database. The use of proprietary SQL, for example, is only a ‘code smell’ if there is a chance that the database will have to be ported to another RDBMS. The use of dynamic SQL is a risk only with certain security models. As the saying goes,  a CodeSmell is a hint of possible bad practice to a pragmatist, but a sure sign of bad practice to a purist. Plamen Ratchev’s wonderful article Ten Common SQL Programming Mistakes lists some of these ‘code smells’ along with out-and-out mistakes, but there are more. The use of nested transactions, for example, isn’t entirely incorrect, even though the database engine ignores all but the outermost: but it does flag up the possibility that the programmer thinks that nested transactions are supported. If anything requires some sort of general agreement, the definition of code smells is one. I’m therefore going to make this Blog ‘dynamic, in that, if anyone twitters a suggestion with a #SQLCodeSmells tag (or sends me a twitter) I’ll update the list here. If you add a comment to the blog with a suggestion of what should be added or removed, I’ll do my best to oblige. In other words, I’ll try to keep this blog up to date. The name against each 'smell' is the name of the person who Twittered me, commented about or who has written about the 'smell'. it does not imply that they were the first ever to think of the smell! Use of deprecated syntax such as *= (Dave Howard) Denormalisation that requires the shredding of the contents of columns. (Merrill Aldrich) Contrived interfaces Use of deprecated datatypes such as TEXT/NTEXT (Dave Howard) Datatype mis-matches in predicates that rely on implicit conversion.(Plamen Ratchev) Using Correlated subqueries instead of a join   (Dave_Levy/ Plamen Ratchev) The use of Hints in queries, especially NOLOCK (Dave Howard /Mike Reigler) Few or No comments. Use of functions in a WHERE clause. (Anil Das) Overuse of scalar UDFs (Dave Howard, Plamen Ratchev) Excessive ‘overloading’ of routines. The use of Exec xp_cmdShell (Merrill Aldrich) Excessive use of brackets. (Dave Levy) Lack of the use of a semicolon to terminate statements Use of non-SARGable functions on indexed columns in predicates (Plamen Ratchev) Duplicated code, or strikingly similar code. Misuse of SELECT * (Plamen Ratchev) Overuse of Cursors (Everyone. Special mention to Dave Levy & Adrian Hills) Overuse of CLR routines when not necessary (Sam Stange) Same column name in different tables with different datatypes. (Ian Stirk) Use of ‘broken’ functions such as ‘ISNUMERIC’ without additional checks. Excessive use of the WHILE loop (Merrill Aldrich) INSERT ... EXEC (Merrill Aldrich) The use of stored procedures where a view is sufficient (Merrill Aldrich) Not using two-part object names (Merrill Aldrich) Using INSERT INTO without specifying the columns and their order (Merrill Aldrich) Full outer joins even when they are not needed. (Plamen Ratchev) Huge stored procedures (hundreds/thousands of lines). Stored procedures that can produce different columns, or order of columns in their results, depending on the inputs. Code that is never used. Complex and nested conditionals WHILE (not done) loops without an error exit. Variable name same as the Datatype Vague identifiers. Storing complex data  or list in a character map, bitmap or XML field User procedures with sp_ prefix (Aaron Bertrand)Views that reference views that reference views that reference views (Aaron Bertrand) Inappropriate use of sql_variant (Neil Hambly) Errors with identity scope using SCOPE_IDENTITY @@IDENTITY or IDENT_CURRENT (Neil Hambly, Aaron Bertrand) Schemas that involve multiple dated copies of the same table instead of partitions (Matt Whitfield-Atlantis UK) Scalar UDFs that do data lookups (poor man's join) (Matt Whitfield-Atlantis UK) Code that allows SQL Injection (Mladen Prajdic) Tables without clustered indexes (Matt Whitfield-Atlantis UK) Use of "SELECT DISTINCT" to mask a join problem (Nick Harrison) Multiple stored procedures with nearly identical implementation. (Nick Harrison) Excessive column aliasing may point to a problem or it could be a mapping implementation. (Nick Harrison) Joining "too many" tables in a query. (Nick Harrison) Stored procedure returning more than one record set. (Nick Harrison) A NOT LIKE condition (Nick Harrison) excessive "OR" conditions. (Nick Harrison) User procedures with sp_ prefix (Aaron Bertrand) Views that reference views that reference views that reference views (Aaron Bertrand) sp_OACreate or anything related to it (Bill Fellows) Prefixing names with tbl_, vw_, fn_, and usp_ ('tibbling') (Jeremiah Peschka) Aliases that go a,b,c,d,e... (Dave Levy/Diane McNurlan) Overweight Queries (e.g. 4 inner joins, 8 left joins, 4 derived tables, 10 subqueries, 8 clustered GUIDs, 2 UDFs, 6 case statements = 1 query) (Robert L Davis) Order by 3,2 (Dave Levy) MultiStatement Table functions which are then filtered 'Sel * from Udf() where Udf.Col = Something' (Dave Ballantyne) running a SQL 2008 system in SQL 2000 compatibility mode(John Stafford)

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• Wrapping ASP.NET Client Callbacks

  - by Ricardo Peres

  Client Callbacks are probably the less known (and I dare say, less loved) of all the AJAX options in ASP.NET, which also include the UpdatePanel, Page Methods and Web Services. The reason for that, I believe, is it’s relative complexity: Get a reference to a JavaScript function; Dynamically register function that calls the above reference; Have a JavaScript handler call the registered function. However, it has some the nice advantage of being self-contained, that is, doesn’t need additional files, such as web services, JavaScript libraries, etc, or static methods declared on a page, or any kind of attributes. So, here’s what I want to do: Have a DOM element which exposes a method that is executed server side, passing it a string and returning a string; Have a server-side event that handles the client-side call; Have two client-side user-supplied callback functions for handling the success and error results. I’m going to develop a custom control without user interface that does the registration of the client JavaScript method as well as a server-side event that can be hooked by some handler on a page. My markup will look like this: 1: <script type="text/javascript"> 1:  2:  3: function onCallbackSuccess(result, context) 4: { 5: } 6:  7: function onCallbackError(error, context) 8: { 9: } 10:  </script> 2: <my:CallbackControl runat="server" ID="callback" SendAllData="true" OnCallback="OnCallback"/> The control itself looks like this: 1: public class CallbackControl : Control, ICallbackEventHandler 2: { 3: #region Public constructor 4: public CallbackControl() 5: { 6: this.SendAllData = false; 7: this.Async = true; 8: } 9: #endregion 10:  11: #region Public properties and events 12: public event EventHandler<CallbackEventArgs> Callback; 13:  14: [DefaultValue(true)] 15: public Boolean Async 16: { 17: get; 18: set; 19: } 20:  21: [DefaultValue(false)] 22: public Boolean SendAllData 23: { 24: get; 25: set; 26: } 27:  28: #endregion 29:  30: #region Protected override methods 31:  32: protected override void Render(HtmlTextWriter writer) 33: { 34: writer.AddAttribute(HtmlTextWriterAttribute.Id, this.ClientID); 35: writer.RenderBeginTag(HtmlTextWriterTag.Span); 36:  37: base.Render(writer); 38:  39: writer.RenderEndTag(); 40: } 41:  42: protected override void OnInit(EventArgs e) 43: { 44: String reference = this.Page.ClientScript.GetCallbackEventReference(this, "arg", "onCallbackSuccess", "context", "onCallbackError", this.Async); 45: String script = String.Concat("\ndocument.getElementById('", this.ClientID, "').callback = function(arg, context, onCallbackSuccess, onCallbackError){", ((this.SendAllData == true) ? "__theFormPostCollection.length = 0; __theFormPostData = ''; WebForm_InitCallback(); " : String.Empty), reference, ";};\n"); 46:  47: this.Page.ClientScript.RegisterStartupScript(this.GetType(), String.Concat("callback", this.ClientID), script, true); 48:  49: base.OnInit(e); 50: } 51:  52: #endregion 53:  54: #region Protected virtual methods 55: protected virtual void OnCallback(CallbackEventArgs args) 56: { 57: EventHandler<CallbackEventArgs> handler = this.Callback; 58:  59: if (handler != null) 60: { 61: handler(this, args); 62: } 63: } 64:  65: #endregion 66:  67: #region ICallbackEventHandler Members 68:  69: String ICallbackEventHandler.GetCallbackResult() 70: { 71: CallbackEventArgs args = new CallbackEventArgs(this.Context.Items["Data"] as String); 72:  73: this.OnCallback(args); 74:  75: return (args.Result); 76: } 77:  78: void ICallbackEventHandler.RaiseCallbackEvent(String eventArgument) 79: { 80: this.Context.Items["Data"] = eventArgument; 81: } 82:  83: #endregion 84: } And the event argument class: 1: [Serializable] 2: public class CallbackEventArgs : EventArgs 3: { 4: public CallbackEventArgs(String argument) 5: { 6: this.Argument = argument; 7: this.Result = String.Empty; 8: } 9:  10: public String Argument 11: { 12: get; 13: private set; 14: } 15:  16: public String Result 17: { 18: get; 19: set; 20: } 21: } You will notice two properties on the CallbackControl: Async: indicates if the call should be made asynchronously or synchronously (the default); SendAllData: indicates if the callback call will include the view and control state of all of the controls on the page, so that, on the server side, they will have their properties set when the Callback event is fired. The CallbackEventArgs class exposes two properties: Argument: the read-only argument passed to the client-side function; Result: the result to return to the client-side callback function, set from the Callback event handler. An example of an handler for the Callback event would be: 1: protected void OnCallback(Object sender, CallbackEventArgs e) 2: { 3: e.Result = String.Join(String.Empty, e.Argument.Reverse()); 4: } Finally, in order to fire the Callback event from the client, you only need this: 1: <input type="text" id="input"/> 2: <input type="button" value="Get Result" onclick="document.getElementById('callback').callback(callback(document.getElementById('input').value, 'context', onCallbackSuccess, onCallbackError))"/> The syntax of the callback function is: arg: some string argument; context: some context that will be passed to the callback functions (success or failure); callbackSuccessFunction: some function that will be called when the callback succeeds; callbackFailureFunction: some function that will be called if the callback fails for some reason. Give it a try and see if it helps!

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• New Features in ASP.NET Web API 2 - Part I

  - by dwahlin

  I’m a big fan of ASP.NET Web API. It provides a quick yet powerful way to build RESTful HTTP services that can easily be consumed by a variety of clients. While it’s simple to get started using, it has a wealth of features such as filters, formatters, and message handlers that can be used to extend it when needed. In this post I’m going to provide a quick walk-through of some of the key new features in version 2. I’ll focus on some two of my favorite features that are related to routing and HTTP responses and cover additional features in a future post.   Attribute Routing Routing has been a core feature of Web API since it’s initial release and something that’s built into new Web API projects out-of-the-box. However, there are a few scenarios where defining routes can be challenging such as nested routes (more on that in a moment) and any situation where a lot of custom routes have to be defined. For this example, let’s assume that you’d like to define the following nested route:   /customers/1/orders   This type of route would select a customer with an Id of 1 and then return all of their orders. Defining this type of route in the standard WebApiConfig class is certainly possible, but it isn’t the easiest thing to do for people who don’t understand routing well. Here’s an example of how the route shown above could be defined:   public static class WebApiConfig { public static void Register(HttpConfiguration config) { config.Routes.MapHttpRoute( name: "CustomerOrdersApiGet", routeTemplate: "api/customers/{custID}/orders", defaults: new { custID = 0, controller = "Customers", action = "Orders" } ); config.Routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } ); GlobalConfiguration.Configuration.Formatters.Insert(0, new JsonpFormatter()); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   With attribute based routing, defining these types of nested routes is greatly simplified. To get started you first need to make a call to the new MapHttpAttributeRoutes() method in the standard WebApiConfig class (or a custom class that you may have created that defines your routes) as shown next:   public static class WebApiConfig { public static void Register(HttpConfiguration config) { // Allow for attribute based routes config.MapHttpAttributeRoutes(); config.Routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } ); } } Once attribute based routes are configured, you can apply the Route attribute to one or more controller actions. Here’s an example:   [HttpGet] [Route("customers/{custId:int}/orders")] public List<Order> Orders(int custId) { var orders = _Repository.GetOrders(custId); if (orders == null) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.NotFound)); } return orders; }   This example maps the custId route parameter to the custId parameter in the Orders() method and also ensures that the route parameter is typed as an integer. The Orders() method can be called using the following route: /customers/2/orders   While this is extremely easy to use and gets the job done, it doesn’t include the default “api” string on the front of the route that you might be used to seeing. You could add “api” in front of the route and make it “api/customers/{custId:int}/orders” but then you’d have to repeat that across other attribute-based routes as well. To simply this type of task you can add the RoutePrefix attribute above the controller class as shown next so that “api” (or whatever the custom starting point of your route is) is applied to all attribute routes: [RoutePrefix("api")] public class CustomersController : ApiController { [HttpGet] [Route("customers/{custId:int}/orders")] public List<Order> Orders(int custId) { var orders = _Repository.GetOrders(custId); if (orders == null) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.NotFound)); } return orders; } }   There’s much more that you can do with attribute-based routing in ASP.NET. Check out the following post by Mike Wasson for more details.   Returning Responses with IHttpActionResult The first version of Web API provided a way to return custom HttpResponseMessage objects which were pretty easy to use overall. However, Web API 2 now wraps some of the functionality available in version 1 to simplify the process even more. A new interface named IHttpActionResult (similar to ActionResult in ASP.NET MVC) has been introduced which can be used as the return type for Web API controller actions. To return a custom response you can use new helper methods exposed through ApiController such as: Ok NotFound Exception Unauthorized BadRequest Conflict Redirect InvalidModelState Here’s an example of how IHttpActionResult and the helper methods can be used to cleanup code. This is the typical way to return a custom HTTP response in version 1:   public HttpResponseMessage Delete(int id) { var status = _Repository.DeleteCustomer(id); if (status) { return new HttpResponseMessage(HttpStatusCode.OK); } else { throw new HttpResponseException(HttpStatusCode.NotFound); } } With version 2 we can replace HttpResponseMessage with IHttpActionResult and simplify the code quite a bit:   public IHttpActionResult Delete(int id) { var status = _Repository.DeleteCustomer(id); if (status) { //return new HttpResponseMessage(HttpStatusCode.OK); return Ok(); } else { //throw new HttpResponseException(HttpStatusCode.NotFound); return NotFound(); } } You can also cleanup post (insert) operations as well using the helper methods. Here’s a version 1 post action:   public HttpResponseMessage Post([FromBody]Customer cust) { var newCust = _Repository.InsertCustomer(cust); if (newCust != null) { var msg = new HttpResponseMessage(HttpStatusCode.Created); msg.Headers.Location = new Uri(Request.RequestUri + newCust.ID.ToString()); return msg; } else { throw new HttpResponseException(HttpStatusCode.Conflict); } } This is what the code looks like in version 2:   public IHttpActionResult Post([FromBody]Customer cust) { var newCust = _Repository.InsertCustomer(cust); if (newCust != null) { return Created<Customer>(Request.RequestUri + newCust.ID.ToString(), newCust); } else { return Conflict(); } } More details on IHttpActionResult and the different helper methods provided by the ApiController base class can be found here. Conclusion Although there are several additional features available in Web API 2 that I could cover (CORS support for example), this post focused on two of my favorites features. If you have .NET 4.5.1 available then I definitely recommend checking the new features out. Additional articles that cover features in ASP.NET Web API 2 can be found here.

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• API Message Localization

  - by Jesse Taber

  In my post, “Keep Localizable Strings Close To Your Users” I talked about the internationalization and localization difficulties that can arise when you sprinkle static localizable strings throughout the different logical layers of an application. The main point of that post is that you should have your localizable strings reside as close to the user-facing modules of your application as possible. For example, if you’re developing an ASP .NET web forms application all of the localizable strings should be kept in .resx files that are associated with the .aspx views of the application. In this post I want to talk about how this same concept can be applied when designing and developing APIs. An API Facilitates Machine-to-Machine Interaction You can typically think about a web, desktop, or mobile application as a collection “views” or “screens” through which users interact with the underlying logic and data. The application can be designed based on the assumption that there will be a human being on the other end of the screen working the controls. You are designing a machine-to-person interaction and the application should be built in a way that facilitates the user’s clear understanding of what is going on. Dates should be be formatted in a way that the user will be familiar with, messages should be presented in the user’s preferred language, etc. When building an API, however, there are no screens and you can’t make assumptions about who or what is on the other end of each call. An API is, by definition, a machine-to-machine interaction. A machine-to-machine interaction should be built in a way that facilitates a clear and unambiguous understanding of what is going on. Dates and numbers should be formatted in predictable and standard ways (e.g. ISO 8601 dates) and messages should be presented in machine-parseable formats. For example, consider an API for a time tracking system that exposes a resource for creating a new time entry. The JSON for creating a new time entry for a user might look like: 1: { 2: "userId": 4532, 3: "startDateUtc": "2012-10-22T14:01:54.98432Z", 4: "endDateUtc": "2012-10-22T11:34:45.29321Z" 5: }   Note how the parameters for start and end date are both expressed as ISO 8601 compliant dates in UTC. Using a date format like this in our API leaves little room for ambiguity. It’s also important to note that using ISO 8601 dates is a much, much saner thing than the \/Date(<milliseconds since epoch>)\/ nonsense that is sometimes used in JSON serialization. Probably the most important thing to note about the JSON snippet above is the fact that the end date comes before the start date! The API should recognize that and disallow the time entry from being created, returning an error to the caller. You might inclined to send a response that looks something like this: 1: { 2: "errors": [ {"message" : "The end date must come after the start date"}] 3: }   While this may seem like an appropriate thing to do there are a few problems with this approach: What if there is a user somewhere on the other end of the API call that doesn’t speak English?  What if the message provided here won’t fit properly within the UI of the application that made the API call? What if the verbiage of the message isn’t consistent with the rest of the application that made the API call? What if there is no user directly on the other end of the API call (e.g. this is a batch job uploading time entries once per night unattended)? The API knows nothing about the context from which the call was made. There are steps you could take to given the API some context (e.g.allow the caller to send along a language code indicating the language that the end user speaks), but that will only get you so far. As the designer of the API you could make some assumptions about how the API will be called, but if we start making assumptions we could very easily make the wrong assumptions. In this situation it’s best to make no assumptions and simply design the API in such a way that the caller has the responsibility to convey error messages in a manner that is appropriate for the context in which the error was raised. You would work around some of these problems by allowing callers to add metadata to each request describing the context from which the call is being made (e.g. accepting a ‘locale’ parameter denoting the desired language), but that will add needless clutter and complexity. It’s better to keep the API simple and push those context-specific concerns down to the caller whenever possible. For our very simple time entry example, this can be done by simply changing our error message response to look like this: 1: { 2: "errors": [ {"code": 100}] 3: }   By changing our error error from exposing a string to a numeric code that is easily parseable by another application, we’ve placed all of the responsibility for conveying the actual meaning of the error message on the caller. It’s best to have the caller be responsible for conveying this meaning because the caller understands the context much better than the API does. Now the caller can see error code 100, know that it means that the end date submitted falls before the start date and take appropriate action. Now all of the problems listed out above are non-issues because the caller can simply translate the error code of ‘100’ into the proper action and message for the current context. The numeric code representation of the error is a much better way to facilitate the machine-to-machine interaction that the API is meant to facilitate. An API Does Have Human Users While APIs should be built for machine-to-machine interaction, people still need to wire these interactions together. As a programmer building a client application that will consume the time entry API I would find it frustrating to have to go dig through the API documentation every time I encounter a new error code (assuming the documentation exists and is accurate). The numeric error code approach hurts the discoverability of the API and makes it painful to integrate with. We can help ease this pain by merging our two approaches: 1: { 2: "errors": [ {"code": 100, "message" : "The end date must come after the start date"}] 3: }   Now we have an easily parseable numeric error code for the machine-to-machine interaction that the API is meant to facilitate and a human-readable message for programmers working with the API. The human-readable message here is not intended to be viewed by end-users of the API and as such is not really a “localizable string” in my opinion. We could opt to expose a locale parameter for all API methods and store translations for all error messages, but that’s a lot of extra effort and overhead that doesn’t add a lot real value to the API. I might be a bit of an “ugly American”, but I think it’s probably fine to have the API return English messages when the target for those messages is a programmer. When resources are limited (which they always are), I’d argue that you’re better off hard-coding these messages in English and putting more effort into building more useful features, improving security, tweaking performance, etc.

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• New OFM versions released SOA Suite 11.1.1.4 &amp; BPM 11.1.1.4 &amp; JDeveloper 11.1.1.4 WebLogic on JRockit 10.3.4 feedback from the community

  - by Jürgen Kress

  Oracle SOA Suite 11g Installations This is the latest release of the Oracle SOA Suite 11g. Please see the Documentation tab for Release Notes, Installation Guides and other release specific information. Please also see the List of New Features and Samples provided for this release. Release 11gR1 (11.1.1.4.0) Microsoft Windows (32-bit JVM) Linux (32-bit JVM) Generic Oracle JDeveloper 11g Rel 1 (11.1.1.x) (JDeveloper + ADF) Integrated development environment certified on Windows, Linux, and Macintosh. License is free (read the Pricing FAQ). Studio Edition for Windows (1.2 GB) | Studio Edition for Linux (1.3 GB) | See All See Additional Development Tools Oracle WebLogic Server 11g Rel 1 (10.3.4) Installers The WebLogic Server installers include Oracle Coherence and Oracle Enterprise Pack for Eclipse and supports development with other Fusion Middleware products . The zip includes WebLogic Server only and is intended for WebLogic Server development only. Linux x86 (1.1 GB) | Windows x86 (1 GB) Zip for Windows x86, Linux x86, Mac OS X (316 MB) | See All Oracle WebLogic Server 11gR1 (10.3.4) on JRockit Virtual Edition Download For additional downloads please visit the Oracle Fusion Middleware Products Update Center Share your feedback with the @soacommunity on twitter SOASimone Simone Geib SOA Suite 11gR1 (11.1.1.4.0) has just been released: http://www.oracle.com/technetwork/middleware/soasuite/downloads/index.html gschmutz gschmutz My new blog post: WebLogic Server, JDev, SOA, BPM, OSB and CEP 11.1.1.4 (PS3) available! - http://tinyurl.com/4negnpn simon_haslam Simon Haslam I'm very pleased to see WLS 10.3.4 for JRockit VE launched at the same time as the rest of PS3 http://j.mp/gl1nQm (32bit anyway) lucasjellema Lucas Jellema See http://www.oracle.com/ocom/groups/public/@otn/documents/webcontent/156082.xml for PS3 extension downloads BPM, SOA Editor, WebCenter demed demed List of new features in @OracleSOA 11gR1 PS3: http://bit.ly/fVRwsP is not extremely long but huge release by # of bugs fixed. Go! biemond Edwin Biemond WebLogic 10.3.4 new features http://bit.ly/f7L1Eu Exalogic Elastic Cloud , JPA2 , Maven plugin, OWSM policies on WebLogic SCA applications JDeveloper JDeveloper & ADF JDeveloper and Oracle ADF 11g Release 1 Patch Set 3 (11.1.1.4.0): New Features and Bug Fixes http://bit.ly/feghnY simon_haslam Simon Haslam WebLogic Server 10.3.4 (i.e. 11gR1 PS3) available now too http://bit.ly/eeysZ2 JDeveloper JDeveloper & ADF Share your impressions on the new JDeveloper 11g Patchset 3 release that came out today! Download it here: http://bit.ly/dogRN8 VikasAatOracle Vikas Anand SOA Suite 11gR1PS3 is Hotpluggable ...see list of features that @Demed posted..#soa #soacommunity   New versions of Oracle Fusion Middleware 11g R1 (11.1.1.4.x)  include: Oracle WebLogic Server 11g R1 (10.3.4) Oracle SOA Suite 11g R1 (11.1.1.4.0) Oracle Business Process Management 11g R1 (11.1.1.4.0) Oracle Complex Event Processing 11g R1 (11.1.1.4.0) Oracle Application Integration Architecture Foundation Pack 11g R1 (11.1.1.4.0) Oracle Service Bus 11g R1 (11.1.1.4.0) Oracle Enterprise Repository 11g R1 (11.1.1.4.0) Oracle Identity Management 11g R1 (11.1.1.4.0) Oracle Enterprise Content Management 11g R1 (11.1.1.4.0) Oracle WebCenter 11g R1 (11.1.1.4.0) - coming soon Oracle Forms, Reports, Portal & Discoverer 11g R1 (11.1.1.4.0) Oracle Repository Creation Utility 11g R1 (11.1.1.4.0) Oracle JDeveloper & Application Development Runtime 11g R1 (11.1.1.4.0) Resources Download  (OTN) Certification Documentation   New Features in Oracle SOA Suite 11g Release 1 (11.1.1.4.0) Updated: January, 2011 Go to Oracle SOA Suite 11g Doc Introduction Oracle SOA Suite 11gR1 (11.1.1.4.0) includes both bug fixes as well as new features listed below - click on the title of each feature for more details. Downloads, documentation links and more information on the Oracle SOA Suite available on the SOA Suite OTN page and as always, we welcome your feedback on the SOA OTN forum. New in Oracle SOA Suite in this release BPEL Component BPEL 2.0 support in JDeveloper The BPEL editor in JDeveloper now generates BPEL 2.0 code and introduces several new activities. Augmented XML variables auto-initialization capabilities The XML variable auto-initialization capabilities have been enhanced to support two need additional use cases: to initialize the to-spec node if it doesn't exist during the rule and to initialize array elements. New Assign Activity dialog The new Assign Activity supports the same drag & drop paradigm used for the XSLT mapper, greatly streamlining the task of assigning multiple variables. Mediator Component Time window parameter for the resequencer This new parameter lets users initiate a best-effort resequencing based on a time window rather than a number of messages. Support for attachments in the Mediator assign dialog The Mediator assign dialog now supports attachment, enabling usage of the Mediator to transmit attachments even if source and target schemas are different. Adapters & Bindings ChunkSize property added to the File Adapter header properties The ChunkSize property of the File Adapter is now available as a header property, allowing in-process modification of the value for this property. Improved support for distributed WLS JMS topics though automatic rebalancing of listeners The JMS Adapter has been enhanced to subscribe to administrative events from WLS JMS. Based on these events, it dynamically rebalances listeners when there are changes to the members of a local or remote WLS JMS distributed destination. JDeveloper configuration wizard for custom JCA adapters A new wizard is available in JDeveloper to configure custom-built adapters Administration & Enterprise Manager Enhanced purging capabilities to manage database growth Historical instance data can now be purged using three different strategies: batch script, scheduled batch script or data partitioning. Asynchronous bulk instance deletion in Enterprise Manager Bulk deletion of instances in Enterprise Manager now executes as an asynchronous operation in Enterprise Manager, returning control to the user as soon as the action has been submitted and acknowledged. B2B Ability to schedule partner downtime This feature allows trading partners to notify each other about planned downtime and to delay delivery of messages during that period. Message sequencing B2B now supports both inbound and outbound message sequencing. Simplified BAM integration with B2B B2B ships with various pre-configured artifacts to simplify monitoring in BAM. Instance Message Java API for B2B The new instance message Java API supports programmatic access to B2B instance message data. Oracle Service Bus (OSB) Certification of the File and FTP JCA Adapters The File and FTP JCA adapters are now certified for use with Oracle Service Bus (in addition to the native transports). Security enhancements Oracle Service Bus now supports SAML 2.0 as well as the OWSM authorization policies. Check the Oracle Service Bus 11.1.1.4 Release Notes for a complete list of new features. Installation, Hot-Pluggability & Certifications Ability to run Oracle SOA Suite on IBM WebSphere Application Server Oracle SOA Suite can now be deployed on IBM WebSphere Application Server Network Deployment (ND) 7.0.11 and IBM WebSphere Application Server 7.0.11. Single JVM developer installation template Oracle SOA Suite can now be targeted to the WebLogic admin server - there is no requirement to also have a managed server. This topology is intended to minimize the memory foorprint of development environments. This is in addition to the list of supported browsers, operating systems and databases already certified in prior releases. Complex Event Processing (CEP) IDE enhancements This release introduces several enhancements to the development IDE, such as adapter wizards and event-type repository. CQL enhancements CQL enhancements include JDBC data cartridges and parametrized queries. Tracing and injecting events in the Event Processing Network (EPN) In the development environment you can now trace and inject events. Check the Oracle CEP 11.1.1.4 Release Notes for a complete list of new features. SOA Suite page on OTN For more information on SOA Specialization and the SOA Partner Community please feel free to register at www.oracle.com/goto/emea/soa (OPN account required) Blog Twitter LinkedIn Mix Forum Wiki Website Technorati Tags: SOA Suite 11.1.1.4,JDeveloper 11.1.1.4,WebLogic 10.3.4,JRockit 10.3.4,SOA Community,Oracle,OPN,SOA,Simone Geib,Guido Schmutz,Edwin Biemond,Lucas Jellema,Simon Haslam,Demed,Vikas Anand,Jürgen Kress

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• Fun with Aggregates

  - by Paul White

  There are interesting things to be learned from even the simplest queries.  For example, imagine you are given the task of writing a query to list AdventureWorks product names where the product has at least one entry in the transaction history table, but fewer than ten. One possible query to meet that specification is: SELECT p.Name FROM Production.Product AS p JOIN Production.TransactionHistory AS th ON p.ProductID = th.ProductID GROUP BY p.ProductID, p.Name HAVING COUNT_BIG(*) < 10; That query correctly returns 23 rows (execution plan and data sample shown below): The execution plan looks a bit different from the written form of the query: the base tables are accessed in reverse order, and the aggregation is performed before the join.  The general idea is to read all rows from the history table, compute the count of rows grouped by ProductID, merge join the results to the Product table on ProductID, and finally filter to only return rows where the count is less than ten. This ‘fully-optimized’ plan has an estimated cost of around 0.33 units.  The reason for the quote marks there is that this plan is not quite as optimal as it could be – surely it would make sense to push the Filter down past the join too?  To answer that, let’s look at some other ways to formulate this query.  This being SQL, there are any number of ways to write logically-equivalent query specifications, so we’ll just look at a couple of interesting ones.  The first query is an attempt to reverse-engineer T-SQL from the optimized query plan shown above.  It joins the result of pre-aggregating the history table to the Product table before filtering: SELECT p.Name FROM ( SELECT th.ProductID, cnt = COUNT_BIG(*) FROM Production.TransactionHistory AS th GROUP BY th.ProductID ) AS q1 JOIN Production.Product AS p ON p.ProductID = q1.ProductID WHERE q1.cnt < 10; Perhaps a little surprisingly, we get a slightly different execution plan: The results are the same (23 rows) but this time the Filter is pushed below the join!  The optimizer chooses nested loops for the join, because the cardinality estimate for rows passing the Filter is a bit low (estimate 1 versus 23 actual), though you can force a merge join with a hint and the Filter still appears below the join.  In yet another variation, the < 10 predicate can be ‘manually pushed’ by specifying it in a HAVING clause in the “q1” sub-query instead of in the WHERE clause as written above. The reason this predicate can be pushed past the join in this query form, but not in the original formulation is simply an optimizer limitation – it does make efforts (primarily during the simplification phase) to encourage logically-equivalent query specifications to produce the same execution plan, but the implementation is not completely comprehensive. Moving on to a second example, the following query specification results from phrasing the requirement as “list the products where there exists fewer than ten correlated rows in the history table”: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) < 10 ); Unfortunately, this query produces an incorrect result (86 rows): The problem is that it lists products with no history rows, though the reasons are interesting.  The COUNT_BIG(*) in the EXISTS clause is a scalar aggregate (meaning there is no GROUP BY clause) and scalar aggregates always produce a value, even when the input is an empty set.  In the case of the COUNT aggregate, the result of aggregating the empty set is zero (the other standard aggregates produce a NULL).  To make the point really clear, let’s look at product 709, which happens to be one for which no history rows exist: -- Scalar aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709;   -- Vector aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709 GROUP BY th.ProductID; The estimated execution plans for these two statements are almost identical: You might expect the Stream Aggregate to have a Group By for the second statement, but this is not the case.  The query includes an equality comparison to a constant value (709), so all qualified rows are guaranteed to have the same value for ProductID and the Group By is optimized away. In fact there are some minor differences between the two plans (the first is auto-parameterized and qualifies for trivial plan, whereas the second is not auto-parameterized and requires cost-based optimization), but there is nothing to indicate that one is a scalar aggregate and the other is a vector aggregate.  This is something I would like to see exposed in show plan so I suggested it on Connect.  Anyway, the results of running the two queries show the difference at runtime: The scalar aggregate (no GROUP BY) returns a result of zero, whereas the vector aggregate (with a GROUP BY clause) returns nothing at all.  Returning to our EXISTS query, we could ‘fix’ it by changing the HAVING clause to reject rows where the scalar aggregate returns zero: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) BETWEEN 1 AND 9 ); The query now returns the correct 23 rows: Unfortunately, the execution plan is less efficient now – it has an estimated cost of 0.78 compared to 0.33 for the earlier plans.  Let’s try adding a redundant GROUP BY instead of changing the HAVING clause: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY th.ProductID HAVING COUNT_BIG(*) < 10 ); Not only do we now get correct results (23 rows), this is the execution plan: I like to compare that plan to quantum physics: if you don’t find it shocking, you haven’t understood it properly :)  The simple addition of a redundant GROUP BY has resulted in the EXISTS form of the query being transformed into exactly the same optimal plan we found earlier.  What’s more, in SQL Server 2008 and later, we can replace the odd-looking GROUP BY with an explicit GROUP BY on the empty set: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ); I offer that as an alternative because some people find it more intuitive (and it perhaps has more geek value too).  Whichever way you prefer, it’s rather satisfying to note that the result of the sub-query does not exist for a particular correlated value where a vector aggregate is used (the scalar COUNT aggregate always returns a value, even if zero, so it always ‘EXISTS’ regardless which ProductID is logically being evaluated). The following query forms also produce the optimal plan and correct results, so long as a vector aggregate is used (you can probably find more equivalent query forms): WHERE Clause SELECT p.Name FROM Production.Product AS p WHERE ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) < 10; APPLY SELECT p.Name FROM Production.Product AS p CROSS APPLY ( SELECT NULL FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ) AS ca (dummy); FROM Clause SELECT q1.Name FROM ( SELECT p.Name, cnt = ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) FROM Production.Product AS p ) AS q1 WHERE q1.cnt < 10; This last example uses SUM(1) instead of COUNT and does not require a vector aggregate…you should be able to work out why :) SELECT q.Name FROM ( SELECT p.Name, cnt = ( SELECT SUM(1) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID ) FROM Production.Product AS p ) AS q WHERE q.cnt < 10; The semantics of SQL aggregates are rather odd in places.  It definitely pays to get to know the rules, and to be careful to check whether your queries are using scalar or vector aggregates.  As we have seen, query plans do not show in which ‘mode’ an aggregate is running and getting it wrong can cause poor performance, wrong results, or both. © 2012 Paul White Twitter: @SQL_Kiwi email: [email protected]

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