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• rewrite not a member of LiftRules

  - by José Leal

  Hi guys, I was following http://www.assembla.com/wiki/show/liftweb/URL_Rewriting tutorial for url rewritting in liftweb.. but I get this error: error: value rewrite is not a member of object net.liftweb.http.LiftRules .. it is really odd.. and the documentation says that it exists. I'm using idea IDE, and I've done everything from scratch, using the lift maven blank archifact. Some more info: [INFO] ------------------------------------------------------------------------ [INFO] Building Joseph3 [INFO] task-segment: [tomcat:run] [INFO] ------------------------------------------------------------------------ [INFO] Preparing tomcat:run [INFO] [resources:resources {execution: default-resources}] [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 0 resource [INFO] [yuicompressor:compress {execution: default}] [INFO] nb warnings: 0, nb errors: 0 [INFO] artifact org.mortbay.jetty:jetty: checking for updates from scala-tools.org [INFO] artifact org.mortbay.jetty:jetty: checking for updates from central [INFO] [compiler:compile {execution: default-compile}] [INFO] Nothing to compile - all classes are up to date [INFO] [scala:compile {execution: default}] [INFO] Checking for multiple versions of scala [INFO] /home/dpz/Scala/Doit/Joseph3/src/main/scala:-1: info: compiling [INFO] Compiling 2 source files to /home/dpz/Scala/Doit/Joseph3/target/classes at 1274922123910 [ERROR] /home/dpz/Scala/Doit/Joseph3/src/main/scala/bootstrap/liftweb/Boot.scala:16: error: value rewrite is not a member of object net.liftweb.http.LiftRules [INFO] LiftRules.rewrite.prepend(NamedPF("ProductExampleRewrite") { [INFO] ^ [ERROR] one error found [INFO] ------------------------------------------------------------------------ [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] wrap: org.apache.commons.exec.ExecuteException: Process exited with an error: 1(Exit value: 1) [INFO] ------------------------------------------------------------------------ [INFO] For more information, run Maven with the -e switch [INFO] ------------------------------------------------------------------------ [INFO] Total time: 19 seconds [INFO] Finished at: Thu May 27 03:02:07 CEST 2010 [INFO] Final Memory: 20M/175M [INFO] ------------------------------------------------------------------------ Process finished with exit code 1 enter code here

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• I write barely functional scripts that tend to not be resuable and make the baby jesus cry. Please h

  - by maxxpower

  I received a request to add around 100 users to a linux box the users are already in ldap so I can't just use newusers and point it at a text file. Another admin is taking care of the ldap piece so all I have to do is create all the home directories and chown them to the correct user once he adds the users to the box. creating the directories isn't a problem, but I'd like a more elegant script for chowning them to the correct user. what I have currently basically looks like chown -R testuser1 testgroup1 /home/tetsuser1; chown -R testuser2 testgroup2 /home/testgroup2; chown -R testsuser3 testgroup1 /home/testuser3 bascially I took the request that the user name and group name popped it into excel added a column of "chown -R" to the front, then added a column of "/", copied and pasted the username column after it and then added a column of ";" and dragged it down to the second to last row. Popped it into notepad ran some quick find and replaces and in less than a minute I have a completed request and a sad empty feeling. I know this was a really ghetto method and I'm trying to get away from using excel to avoid learning new scripting techniques so here's my real question. tl;dr I made 100 home directories and chowned them to the correct users, but it was ugly. Actual question below. You have a file named idlist that looks like this (only with say 1000 users and real usernames and groups) testuser1 testgroup1 testuser2 testgroup2 testuser3 testgroup1 write a script that creates home directories for all the users and chowns the created directories to the correct user and group. To make the directories I used the following(feel free to flame/correct me on this as well. ) var= 'cut -f1 -d" " idlist' (I used backticks not apostrophes around the cut command) mkdir $var

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• A more elegant way to start a multithread alarm in Rebol VID ? (What's the equivalent of load event?

  - by Rebol Tutorial

  I want to trigger an alarm when the GUI starts. I can't see what's the equivalent of load event of other language in Rebol VID, so I put it in the periodic handler which is quite circumvoluted. So how to do this more cleanly ? alarm-data: none set-alarm: func [ "Set alarm for future time." seconds "Seconds from now to ring alarm." message [string! unset!] "Message to print on alarm." ] [ alarm-data: reduce [now/time + seconds message] ] ring: func [ "Action for when alarm comes due." message [string! unset!] ] [ set-face monitor either message [message]["RIIIING!"] ; Your sound playing can also go here (my computer doesn't have speakers). ] periodic: func [ "Called every second, checks alarms." fact action event ] [ either alarm-data [ ; Update alarm countdown. set-face monitor rejoin [ "Alarm will ring in " to integer! alarm-data/1 - now/time " seconds." ] ; Check alarm. if now/time > alarm-data/1 [ ring alarm-data/2 ;alarm-data: none ; Reset once fired. ] ][ either value? 'message [ set-alarm seconds message ][ set-alarm seconds "Alarm triggered!" ] ] ] alarm: func[seconds message [string! unset!]][ system/words/seconds: seconds if value? 'message [ system/words/message: message ] view layout [ monitor: text 256 "" rate 1 feel [engage: :periodic] button 256 "re/start countdown" [ either value? 'message [ set-alarm seconds message ][ set-alarm seconds "Alarm triggered!" ] set-face monitor "Alarm set." ] ] ]

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• Problem with fork exec kill when redirecting output in perl

  - by Edu

  I created a script in perl to run programs with a timeout. If the program being executed takes longer then the timeout than the script kills this program and returns the message "TIMEOUT". The script worked quite well until I decided to redirect the output of the executed program. When the stdout and stderr are being redirected, the program executed by the script is not being killed because it has a pid different than the one I got from fork. It seems perl executes a shell that executes my program in the case of redirection. I would like to have the output redirection but still be able to kill the program in the case of a timeout. Any ideas on how I could do that? A simplified code of my script is: #!/usr/bin/perl use strict; use warnings; use POSIX ":sys_wait_h"; my $timeout = 5; my $cmd = "very_long_program 1>&2 > out.txt"; my $pid = fork(); if( $pid == 0 ) { exec($cmd) or print STDERR "Couldn't exec '$cmd': $!"; exit(2); } my $time = 0; my $kid = waitpid($pid, WNOHANG); while ( $kid == 0 ) { sleep(1); $time ++; $kid = waitpid($pid, WNOHANG); print "Waited $time sec, result $kid\n"; if ($timeout > 0 && $time > $timeout) { print "TIMEOUT!\n"; #Kill process kill 9, $pid; exit(3); } } if ( $kid == -1) { print "Process did not exist\n"; exit(4); } print "Process exited with return code $?\n"; exit($?); Thanks for any help.

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• General many-to-many relationship problem ( Postgresql )

  - by David

  Hi, i have two tables: CREATE TABLE "public"."auctions" ( "id" VARCHAR(255) NOT NULL, "auction_value_key" VARCHAR(255) NOT NULL, "ctime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, "mtime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, CONSTRAINT "pk_XXXX2" PRIMARY KEY("id"), ); and CREATE TABLE "public"."auction_values" ( "id" NUMERIC DEFAULT nextval('default_seq'::regclass) NOT NULL, "fk_auction_value_key" VARCHAR(255) NOT NULL, "key" VARCHAR(255) NOT NULL, "value" TEXT, "ctime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, "mtime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, CONSTRAINT "pk_XXXX1" PRIMARY KEY("id"), ); if i want to create a many-to-many relationship on the auction_value_key like this: ALTER TABLE "public"."auction_values" ADD CONSTRAINT "auction_values_fk" FOREIGN KEY ("fk_auction_value_key") REFERENCES "public"."auctions"("auction_value_key") ON DELETE NO ACTION ON UPDATE NO ACTION NOT DEFERRABLE; i get this SQL error: ERROR: there is no unique constraint matching given keys for referenced table "auctions" Question: As you might see, i want "auction_values" to be be "reused" by different auctions without duplicating them for every auction... So i don't want a key relation on the "id" field in the auctions table... Am i thinking wrong here or what is the deal? ;) Thanks

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• How to design Models the correct way: Object-oriented or "Package"-oriented?

  - by ajsie

  I know that in OOP you want every object (from a class) to be a "thing", eg. user, validator etc. I know the basics about MVC, how they different parts interact with each other. However, i wonder if the models in MVC should be designed according to the traditional OOP design, that is to say, should every model be a database/table/row (solution 2)? Or is the intention more like to collect methods that are affecting the same table or a bunch of related tables (solution 1). example for an Address book module in CodeIgniter, where i want be able to "CRUD" a Contact and add/remove it to/from a CRUD-able Contact Group. Models solution 1: bunching all related methods together (not real object, rather a "package") class Contacts extends Model { function create_contact() {) function read_contact() {} function update_contact() {} function delete_contact() {} function add_contact_to_group() {} function delete_contact_from_group() {} function create_group() {} function read_group() {} function update_group() {} function delete_group() {} } Models solution 2: the OOP way (one class per file) class Contact extends Model { private $name = ''; private $id = ''; function create_contact() {) function read_contact() {} function update_contact() {} function delete_contact() {} } class ContactGroup extends Model { private $name = ''; private $id = ''; function add_contact_to_group() {} function delete_contact_from_group() {} function create_group() {} function read_group() {} function update_group() {} function delete_group() {} } i dont know how to think when i want to create the models. and the above examples are my real tasks for creating an Address book. Should i just bunch all functions together in one class. then the class contains different logic (contact and group), so it can not hold properties that are specific for either one of them. the solution 2 works according to the OOP. but i dont know why i should make such a dividing. what would the benefits be to have a Contact object for example. Its surely not a User object, so why should a Contact "live" with its own state (properties and methods). you experienced guys with OOP/MVC, please shed a light on how one should think here in this very concrete task.

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• Extracting note onset from MIDI

  - by Dolphin

  Hi I need to extract musical features (note details-pitch, duration, rhythm, loudness, note start time) from a polyphonic (having 2 scores for treble and bass - bass may also have chords) MIDI file. I'm using the jMusic API to extract these details from a MIDI file. My approach is to go through each score, into parts, then phrases and finally notes and extract the details. With my approach, it's reading all the treble notes first and then the bass notes - but chords are not captured (i.e. only a single note of the chord is taken), and I cannot identify from which point onwards are the bass notes. So what I tried was to get the note onsets (i.e. the start time of note being played) - since the starting time of both the treble and bass notes at the start of the piece should be same - But I cannot extract the note onset using jMusic API. Each time it shows 0.0. Is there any way I can identify the voice (treble or bass) of a note? And also all the notes of a chord? How is the voice or note onset for each note stored in MIDI? Is this different for each MIDI file? Any insight is greatly appreciated. Thanks in advance

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• Automatic Deployment to Multiple Production Environments

  - by Brandon Montgomery

  I want to update an ASP .NET web application (including web.config file changes and database scripts) to multiple production environments - ideally with the click of a button. I do not have direct network connectivity to any of them. I think this means the application servers will have to "pull" the information required for updating the application, and run a script to update the application that resides on the server. Basically, I need a way to "publish" an update, and the servers see that update and automatically download and run it. I've thought about possibly setting up an SFTP server for publishing updates, and developing a custom tool which is installed on production environments which looks at the SFTP server every day and downloads application files if they are available. That would at least get the required files onto the servers, and I could use xcopy/robocopy and Migrator.NET to deploy the updates. Still not sure about config file changes, but that at least gets me somewhere. Is there any good solution for this scenario? Are there any tools that do this for you?

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• Oracle syntax - should we have to choose between the old and the new?

  - by Martin Milan

  Hi, I work on a code base in the region of about 1'000'000 lines of source, in a team of around eight developers. Our code is basically an application using an Oracle database, but the code has evolved over time (we have plenty of source code from the mid nineties in there!). A dispute has arisen amongst the team over the syntax that we are using for querying the Oracle database. At the moment, the overwhelming majority of our queries use the "old" Oracle Syntax for joins, meaning we have code that looks like this... Example of Inner Join select customers.*, orders.date, orders.value from customers, orders where customers.custid = orders.custid Example of Outer Join select customers.custid, contacts.ContactName, contacts.ContactTelNo from customers, contacts where customers.custid = contacts.custid(+) As new developers have joined the team, we have noticed that some of them seem to prefer using SQL-92 queries, like this: Example of Inner Join select customers.*, orders.date, orders.value from customers inner join orders on (customers.custid = orders.custid) Example of Outer Join select customers.custid, contacts.ContactName, contacts.ContactTelNo from customers left join contacts on (customers.custid = contacts.custid) Group A say that everyone should be using the the "old" syntax - we have lots of code in this format, and we ought to value consistency. We don't have time to go all the way through the code now rewriting database queries, and it wouldn't pay us if we had. They also point out that "this is the way we've always done it, and we're comfortable with it..." Group B however say that they agree that we don't have the time to go back and change existing queries, we really ought to be adopting the "new" syntax on code that we write from here on in. They say that developers only really look at a single query at a time, and that so long as developers know both syntax there is nothing to be gained from rigidly sticking to the old syntax, which might be deprecated at some point in the future. Without declaring with which group my loyalties lie, I am interested in hearing the opinions of impartial observers - so let the games commence! Martin. Ps. I've made this a community wiki so as not to be seen as just blatantly chasing after question points...

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• ASP.NET MVC UpdateModel doesn't update inherited public properties??

  - by mrjoltcola

  I refactored some common properties into a base class and immediately my model updates started failing. UpdateModel() and TryUpdateModel() do not seem to update inherited public properties. I cannot find detailed info on MSDN nor Google as to the rules or semantics of these methods. The docs are terse (http://msdn.microsoft.com/en-us/library/dd470933.aspx), simply stating: Updates the specified model instance using values from the controller's current value provider. Well that leads us to believe it is as simple as that. It makes no mention of limitations with inheritance. My assumption is the methods are reflecting on the top class only, ignoring base properties, but this seems to be an ugly shortcoming, if so. SOLVED: Eep, this turned out to have nothing to do with inheritance. My base class was implemented with public fields, not properties. Switching them to formal properties (adding {get; set; }) was all I needed. This has bitten me before, I keep wanting to use simple, public fields.

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• How do I read text from a serial port?

  - by user2164

  I am trying to read data off of a Windows serial port through Java. I have the javax.comm libraries and am able to get some data but not correct data. When I read the port into a byte array and convert it to text I get a series of characters but no real text string. I have tried to specify the byte array as being both "UTF-8" and "US-ASCII". Does anyone know how to get real text out of this? Here is my code: while (inputStream.available() > 0) { int numBytes = inputStream.read(readBuffer); System.out.println("Reading from " + portId.getName() + ": "); System.out.println("Read " + numBytes + " bytes"); } System.out.println(new String(readBuffer)); System.out.println(new String(readBuffer, "UTF-8")); System.out.println(new String(readBuffer, "US-ASCII")); the output of the first three lines will not let me copy and paste (I assume because they are not normal characters). Here is the output of the Hex: 78786000e67e9e60061e8606781e66e0869e98e086f89898861878809e1e9880 I am reading from a Hollux GPS device which does output in string format. I know this for sure because I did it through C#. The settings that I am using for communication which I know are right from the work in the C# app are: Baud Rate: 9600 Databits: 8 Stop bit: 1 parity: none

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• calling .ajax() from an eventHandler c# asp.ent

  - by ibininja

  Good day...! In the code behind (upload.aspx) I have an event that returns the number of bytes being streamed; and as I debug it, it works fine. I wanted to reflect the numbers returned from the eventHandler on a progress bar and this is where I got lost. I tried using jQuery's .ajax() function. this is how I implemented it: In the EventHandler in my code behind I added this code to call the .ajax() function: Page.ClientScript.RegisterStartupScript(this.GetType(), "UpdateProgress", "<script type='text/javascript'>updateProgress();</script>"); My plan is whenever the eventHandler function changes the values of bytes being streamed it calls the javascript function "updateProgress()" The .ajax() function "UpdateProgress()" is as: function updateProgress() { $.ajax({ type: "POST", url: "upload.aspx/GetData", data: "{}", contentType: "application/json; charset=utf-8", dataType: "json", async: true, success: function (msg) { $("#progressbar").progressbar("option", "value", msg.d); } }); } I made sure that the function GetData() is [System.Web.Services.WebMethod] and that it is static as well. so the workflow of what I am trying to implement is as: - Click On Upload button - The Behind code starts executing and EventHandler triggers - The EventHandler calls .ajax() function - The .ajax() function retrieves the bytes being streamed and updates progress bar. When I ran the code; all runs well except that the .ajax() is only executed when upload is finished (and progress bar also updates only when finished upload); even though I call .ajax() function every time in the eventHandler function as reflected above... What am I doing wrong? Am I thinking of this right? is there anything else I should add maybe an updatePanel or something? thank you

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• What does O(log n) mean exactly?

  - by Andreas Grech

  I am currently learning about Big O Notation running times and amortized times. I understand the notion of O(n) linear time, meaning that the size of the input affects the growth of the algorithm proportionally...and the same goes for, for example, quadratic time O(n2) etc..even algorithms, such as permutation generators, with O(n!) times, that grow by factorials. For example, the following function is O(n) because the algorithm grows in proportion to its input n: f(int n) { int i; for (i = 0; i < n; ++i) printf("%d", i); } Similarly, if there was a nested loop, the time would be O(n2). But what exactly is O(log n)? For example, what does it mean to say that the height of a complete binary tree is O(log n)? I do know (maybe not in great detail) what Logarithm is, in the sense that: log10 100 = 2, but I cannot understand how to identify a function with a logarithmic time.

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• UpdatePanel refreshes only once

  - by superexsl

  Hi, I have two updatepanels inside an accordion control, laid out like this: <accordion> <first pane content> <updatepanel UpdateMode="conditional"> <contenttemplate>...</contenttemplate> <triggers>...</triggers> </updatepanel> </first pane content> <second pane content> <updatepanel> <contenttemplate>...</contenttemplate> <triggers>...</triggers> </updatepanel> </second pane content> </accordion> The panel updates once, but after that, no updates take place. If I refresh the page, then I can see the updated information. This means that the database is being updated, but the updatepanel isn't refreshing (after refreshing the first time). Why is this happening? This has been bugging me for days, so any advice would be much appreciated. Thanks!

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• Important question about linq to SQL performance on high loaded web applications

  - by Alex

  I started working with linq to SQL several weeks ago. I got really tired of working with SQL server directly through the SQL queries (sqldatareader, sqlcommand and all this good stuff).  After hearing about linq to SQL and mvc I quickly moved all my projects to these technologies. I expected linq to SQL work slower but it suprisongly turned out to be pretty fast, primarily because I always forgot to close my connections when using datareaders. Now I don't have to worry about it. But there's one problem that really bothers me. There's one page that's requested thousands of times a day. The system gets data in the beginning, works with it and updates it. Primarily the updates are ++ @ -- (increase and decrease values). I used to do it like this UPDATE table SET value=value+1 WHERE ID=@I'd It worked with no problems obviously. But with linq to SQL the data is taken in the beginning, moved to the class, changed and then saved. Stats.registeredusers++; Db.submitchanges(); Let's say there were 100 000 users. Linq will say "let it be 100 001" instead of "let it be increased by 1". But if there value of users has already been increased (that happens in my site all the time) then linq will be like oops, this value is already 100 001. Whatever I'll throw an exception" You can change this behavior so that it won't throw an exception but it still will not set the value to 100 002. Like I said, it happened with me all the time. The stas value was increased twice a second on average. I simply had to rewrite this chunk of code with classic ado net. So my question is how can you solve the problem with linq

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• Quartz 2D or OpenGL ES? Pros and cons in the long term, possibility of migration to other platforms.

  - by fspirit

  Hi all! I'm having a hard time deciding whether to go with Quartz2D or OpenGL for an iPad game. It will be 2D mostly, but effect-intense (simultaneous lighting effects for 10-30 objects, 10-20 simultaneous animations on the screen). So far, assuming i'm equally dumb in both technologies and have to learn them from the ground, i came to this list. (I've read several topics here, on SO, with names like "Quartz or OpenGL", but i'm still left with some questions) Quartz: Better time-to-market, because of ready to use absractions like UIView, UIImageView, CoreAnimation abstractions Open GL ES Closer to hardware, thus, performance is better. App, implemented with OpenGL ES can be easier migrated to Android, MeeGo, Windows Phone, etc. My questions are: How time will it take to rewrite Quartz 2d app to use OpenGL? Lets say it took me 2 man-month to write Quartz app, how much time will i need to rewrite it? (Please, just some subjective opinions, i'll try to summarize them somehow) Regarding the ease of migration to other platforms, when using OpenGL, is it really so? Or efforts when migrating Quartz app from iPhoneOS to Android will be not so much bigger, compared to OpenGL app migration? (Ease of migration is quite important criterion) Regarding OpenGL, should i go with OpenGL 1.1 or 2.0, concerning migration? (Android supports 2.0 through NDK, but dont know whether NDK's use will increase or decrease migration efforts)

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• how to bind the converted value from a datatable to my gridview.

  - by Ranjana

  how to bind the value to gridview i have a datatable DataTable dtBindGrid = new DataTable(); dtBindGrid = serviceobj.SelectExamTimeTable(txtSchoolName.Text, txtBranchName.Text, txtClass.Text, txtExamName.Text); foreach (DataRow row in dtBindGrid.Rows) { strgetday= row["Day"].ToString(); strgetdate = row["Date"].ToString(); DatedTime = Convert.ToDateTime(row["Time"].ToString()); strgettime = DatedTime.ToString("t"); strgetsubject = row["Subject"].ToString(); strgetduration = row["Duration"].ToString(); strgetsession = row["Session"].ToString(); strgetminmark = row["MinMarks"].ToString(); strgetmaxmark = row["MaxMarks"].ToString(); // dtBindGrid.Rows.Add(row); } GrdExamTimeTable.DataSource = dtBindGrid.DefaultView; GrdExamTimeTable.DataBind(); this datatable will return me some values like day,date,time,duration,subject,.. here im getting each value in string bec to convert the Time as 9.00am or 9.00pm DatedTime = Convert.ToDateTime(row["Time"].ToString()); strgettime = DatedTime.ToString("t"); .... how to bind this converted value to my gridview.

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• Java problem: Could not find main class HelloWorld

  - by Newbie

  I am new to java(a real novice). I installed Java 1.7.0 in the following folder C:\Program Files\Java The environment variable which I set are CLASSPATH : C:\Program Files\Java\jdk1.7.0\jre\lib\rt.jar; Path : C:\Program Files\Java\jdk1.7.0\bin; JAVA_HOME : C:\Program Files\Java; I have presented here the class names which are in my system. Next I wrote a program(HelloWorld.java) import java.io.*; class HelloWorld { public static void main(String[] args) { System.out.println("Hello World!"); } } When I am compiling using javac HelloWorld.java it is compiling fine. But after I issue java HelloWorld I am encountering the below error Error: Could not find main class HelloWorld Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:198) Caused by: java.lang.ClassNotFoundException: HelloWorld at java.net.URLClassLoader$1.run(URLClassLoader.java:299) at java.net.URLClassLoader$1.run(URLClassLoader.java:288) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:287) at java.lang.ClassLoader.loadClass(ClassLoader.java:422) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:325) at java.lang.ClassLoader.loadClass(ClassLoader.java:355) at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:195) After a bit of google search I found that may be something wrong in the environment variable. I tried to play with that but no luck. I know that it may be a very simple thing for the real java developers(actually basic) but for me as of now no luck! I even RESTARTED the machine and then again I tried to run but with same fate. OS: Windows XP(Version 2002) with Service pack 3 Help needed . Thanks .

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• How to store a list in a column of a database table.

  - by John Berryman

  Howdy! So, per Mehrdad's answer to a related question, I get it that a "proper" database table column doesn't store a list. Rather, you should create another table that effectively holds the elements of said list and then link to it directly or through a junction table. However, the type of list I want to create will be composed of unique items (unlike the linked question's fruit example). Furthermore, the items in my list are explicitly sorted - which means that if I stored the elements in another table, I'd have to sort them every time I accessed them. Finally, the list is basically atomic in that any time I wish to access the list, I will want to access the entire list rather than just a piece of it - so it seems silly to have to issue a database query to gather together pieces of the list. AKX's solution (linked above) is to serialize the list and store it in a binary column. But this also seems inconvenient because it means that I have to worry about serialization and deserialization. Is there any better solution? If there is no better solution, then why? It seems that this problem should come up from time to time. ... just a little more info to let you know where I'm coming from. As soon as I had just begun understanding SQL and databases in general, I was turned on to LINQ to SQL, and so now I'm a little spoiled because I expect to deal with my programming object model without having to think about how the objects are queried or stored in the database. Thanks All! John

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• Mysql Server Optimization

  - by Ish Kumar

  Hi Geeks, We are having serious MySQL(InnoDB) performance issues at a moment when we do: (10-20) insertions on TABLE1 (10-20) updates on TABLE2 Note: Both above operations happens within fraction of a second. And this occurs every few (10-15) minutes. And all online users (approx 400-600) doing read operation on join of TABLE1 & TABLE2 every 1 second. Here is our mysql configuration info: http://docs.google.com/View?id=dfrswh7c_117fmgcmb44 Issues: Lot queries wait and expire later (saw it from phpmyadmin / processes). My poor MySQL server crashes sometimes Questions Q1: Any suggestions to optimize at MySQL level? Q2: I thinking to use persistent connections at application level, is it right? Info Added Later: Database Engine: InnoDB TABLE1 : 400,000 rows (inserting 8,000 daily) & TABLE2: 8,000 rows 1 second query: SELECT b.id, b.user_id, b.description, b.debit, b.created, b.price, u.username, u.email, u.mobile FROM TABLE1 b, TABLE2 u WHERE b.credit = 0 AND b.user_id = u.id AND b.auction_id = "12345" ORDER BY b.id DESC LIMIT 10; // there are few more but they are not so critical. Indexing is good, we are using them wisely. In above query all id's are indexed And TABLE1 has frequent insertions and TABLE2 has frequent updates.

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• How to merge duplicates in 2D python arrays

  - by Wei Lou

  Hi, I have a set of data similar to this: No Start Time End Time CallType Info 1 13:14:37.236 13:14:53.700 Ping1 RTT(Avr):160ms 2 13:14:58.955 13:15:29.984 Ping2 RTT(Avr):40ms 3 13:19:12.754 13:19:14.757 Ping3_1 RTT(Avr):620ms 3 13:19:12.754 Ping3_2 RTT(Avr):210ms 4 13:14:58.955 13:15:29.984 Ping4 RTT(Avr):360ms 5 13:19:12.754 13:19:14.757 Ping1 RTT(Avr):40ms 6 13:19:59.862 13:20:01.522 Ping2 RTT(Avr):163ms ... when i parse through it, i need merge the results of Ping3_1 and Ping3_2. Then take average of those two row export as one row. So the end of result would be like this: No Start Time End Time CallType Info 1 13:14:37.236 13:14:53.700 Ping1 RTT(Avr):160ms 2 13:14:58.955 13:15:29.984 Ping2 RTT(Avr):40ms 3 13:19:12.754 13:19:14.757 Ping3 RTT(Avr):415ms 4 13:14:58.955 13:15:29.984 Ping4 RTT(Avr):360ms 5 13:19:12.754 13:19:14.757 Ping1 RTT(Avr):40ms 6 13:19:59.862 13:20:01.522 Ping2 RTT(Avr):163ms currently i am concatenating column 0 and 1 to make a unique key, find duplication there then doing rest of special treatment for those parallel Pings. It is not elegant at all. Just wonder what is the better way to do it. Thanks!

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• check whether mmap'ed address is correct

  - by reddot

  I'm writing a high-loaded daemon that should be run on the FreeBSD 8.0 and on Linux as well. The main purpose of daemon is to pass files that are requested by their identifier. Identifier is converted into local filename/file size via request to db. And then I use sequential mmap() calls to pass file blocks with send(). However sometimes there are mismatch of filesize in db and filesize on filesystem (realsize < size in db). In this situation I've sent all real data blocks and when next data block is mapped -- mmap returns no errors, just usual address (I've checked errno variable also, it's equal to zero after mmap). And when daemon tries to send this block it gets Segmentation Fault. (This behaviour is guarantedly issued on FreeBSD 8.0 amd64) I was using safe check before open to ensure size with stat() call. However real life shows to me that segfault still can be raised in rare situtaions. So, my question is there a way to check whether pointer is accessible before dereferencing it? When I've opened core in gdb, gdb says that given address is out of bound. Probably there is another solution somebody can propose.

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• Best way to randomly select rows *per* column in SQL Server

  - by LesterDove

  A search of SO yields many results describing how to select random rows of data from a database table. My requirement is a bit different, though, in that I'd like to select individual columns from across random rows in the most efficient/random/interesting way possible. To better illustrate: I have a large Customers table, and from that I'd like to generate a bunch of fictitious demo Customer records that aren't real people. I'm thinking of just querying randomly from the Customers table, and then randomly pairing FirstNames with LastNames, Address, City, State, etc. So if this is my real Customer data (simplified): FirstName LastName State ========================== Sally Simpson SD Will Warren WI Mike Malone MN Kelly Kline KS Then I'd generate several records that look like this: FirstName LastName State ========================== Sally Warren MN Kelly Malone SD Etc. My initial approach works, but it lacks the elegance that I'm hoping the final answer will provide. (I'm particularly unhappy with the repetitiveness of the subqueries, and the fact that this solution requires a known/fixed number of fields and therefore isn't reusable.) SELECT FirstName = (SELECT TOP 1 FirstName FROM Customer ORDER BY newid()), LastName= (SELECT TOP 1 LastNameFROM Customer ORDER BY newid()), State = (SELECT TOP 1 State FROM Customer ORDER BY newid()) Thanks!

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• Problem with load testing Web Service - VSTS 2008

  - by Carlos

  Hello, I have a webtest with makes a simple call to a WebService which looks like that: MyWebService webService = new MyWebService(); webService.Timeout = 180000; webService.myMethod(); I am not using ThinkTimes, also the Run Duration is set to 5 minutes. When I ran this test simulating only 1 user, I check the counters and I found something like that: Tests Total: 4500 Network Interface\Bytes sent (agent machine): 35,500 Then I ran the same tests, but this time simulating 2 users and I got something like that: Tests Total: 2225 Network Interface\Bytes sent (agent machine): 30,500 So when I increased the numbers of users the tests/sec was half than when I use only 1 user and the bytes sent by the agent was also lower. I think it is strange, because it doesn't seems I have a bottleneck in my agent machine since CPU is never higher than 30% and I have over 1.5GB of RAM free, also my network utilization is like 0.5% of its capacity. In order to troubleshot this I ran a test using Step Pattern, the simulated users went from 20 to 800 users. When I check the requests/sec it is practically constant through the whole test, so it is clear there is something in my test or my environment which is preventing the number of requests from gets higher. It would be a expected behavior if the "response time" was getting higher because it would tell me the requests wasn't been processed properly, but the strange thing is the response time is practically constant all the time and it is pretty low actually. I have no idea why my agent can't send more requests when I increase the numbers of users, any help/tip/guess would be really appreciate.

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• Record Disappeared from Mysql Table, How Can I Find Out What Happened?

  - by Jascha

  I got the fire alarm phone call, AIM messages and email today from a client stating "The site is down!, WTF happened?!" Well, after a little digging, it turns out one of the records in a table had been wiped clean, but without removing the row itself. So, I had the representation of data, but a bunch of empty fields. (needless to day I need to write into my code a catch for this.) What my real question is, where can I figure out what happened? I've got access to phpmyadmin and that's about it. I found some access logs on in the root directory of my server, but that just tells me the client was in the admin area I built editing that record, I'd like to know specifically what they did that made all of the data go away. (what query was run etc...) is it possible without real server admin access? is there a neat little php to mysql class that returns data like this? Thanks in advance. -Jascha

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