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• How can I specify dependencies in the manifest file and then to include it into my .jar file?

  - by Roman

  I generated .class files by the following command: javac -cp \directoryName\external.jar myPackageDirectory\First.java myPackageDirectory\Second.java I needed to use -cp during compilation and name of .jar file of an "external" library (external.jar) to be able to use this library from my code. Using my .class files I have generated my .jar file in the following way: jar cfm app.jar manifest.txt myPackageDirectory\*.class manifest.txt contains just one line: Main-Class: myPackageName.First My problem is that I am not sure that I will be able to run my .jar file on other computers. I think so because during the compilation I specified the location of the .jar file of the external library. So, my .class files (included into the .jar file will try to find the .jar file of the external library in a specific directory and there is no guaranty that that the .jar file of the external library will be in the same directory as on the my computer. I heard that the above problem can be solved by a usage of a MANIFEST file that I include in my own jar, and which will list dependency locations but I do not understand how it works. I do need to specify location of the "external.jar" at the compilation stage (otherwise the compiler complains).

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• JarEntry.getSize() is returning -1 when the jar files is opened as InputStream from URL

  - by Reshma Donthireddy

  I am trying to read file from the JarInputStream and the size of file is returning -1. I am accessing Jar file from the URL as a inputStream. URLConnection con = url.openConnection(); JarInputStream jis = new JarInputStream(con.getInputStream()); JarEntry je = null; while ((je = jis.getNextJarEntry()) != null) { htSizes.put(je.getName(), new Integer((int) je.getSize())); if (je.isDirectory()) { continue; } int size = (int) je.getSize(); // -1 means unknown size. if (size == -1) { size = ((Integer) htSizes.get(je.getName())).intValue(); } byte[] b = new byte[(int) size]; int rb = 0; int chunk = 0; while (((int) size - rb) > 0) { chunk = jis.read(b, rb, (int) size - rb); if (chunk == -1) { break; } rb += chunk; } // add to internal resource hashtable htJarContents.put(je.getName(), baos.toByteArray()); }

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• Javascript/Jquery pop-up window in Asp.Net MVC4

  - by Mark

  Below I have a "button" (just a span with an icon) that creates a pop-up view of a div in my application to allow users to compare information in seperate windows. However, I get and Asp.Net Error as follows: **Server Error in '/' Application. The resource cannot be found. Requested URL: /Home/[object Object]** Does anyone have an Idea of why this is happending? Below is my code: <div class="module_actions"> <div class="actions"> <span class="icon-expand2 pop-out"></span> </div> </div> <script> $(document).ajaxSuccess(function () { var Clone = $(".pop-out").click(function () { $(this).parents(".module").clone().appendTo("#NewWindow"); }); $(".pop-out").click(function popitup(url) { LeftPosition = (screen.width) ? (screen.width - 400) / 1 : 0; TopPosition = (screen.height) ? (screen.height - 700) / 1 : 0; var sheight = (screen.height) * 0.5; var swidth = (screen.width) * 0.5; settings = 'height=' + sheight + ',width=' + swidth + ',top=' + TopPosition + ',left=' + LeftPosition + ',scrollbars=yes,resizable=yes,toolbar=no,status=no,menu=no, directories=no,titlebar=no,location=no,addressbar=no' newwindow = window.open(url, '/Index', settings); if (window.focus) { newwindow.focus() } return false; }); });

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• Exploiting Path Traversal Vulnerability

  - by Maputo

  I have a Java Web App running on Tomcat on which I'm supposed to exploit Path traversal vulnerability. There is a section (in the App) at which I can upload a .zip file, which gets extracted in the server's /tmp directory. The content of the .zip file is not being checked, so basically I could put anything in it. I tried putting a .jsp file in it and it extracts perfectly. My problem is that I don't know how to reach this file as a "normal" user from browser. I tried entering ../../../tmp/somepage.jsp in the address bar, but Tomcat just strips the ../ and gives me http://localhost:8080/tmp/ resource not available. Ideal would be if I could somehow rename the somepage.jsp so that it gets extracted in the web directory of the Web App. But then, the Linux filesystem disallows slashes in filenames (e.g. ../../home/webapp/somepage.jsp). Are there maybe any escape sequences that would translate to / after extracting? Any ideas would be highly appreciated. Note: This is a school project in a Security course where I'm supposed to locate vulnerabilities and correct them. Not trying to harm anyone...

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• Strange compiler complaint when using similar code

  - by Jason

  For a project, I have to ask the user for a file name, and I'm reading it in character by character using getchar. From the main, I call the function char *coursename= introPrint(); //start off to print the usage directions and get the first bit of input. That function is defined as char *introPrint(){ int size= 20; int c; int length=0; char buffer[size]; //instructions printout, cut for brevity //get coursename from user and return it while ( (c=getchar()) != EOF && (c != '\n') ){ buffer[length++]= c; if (length==size-1) break; } buffer[length]=0; return buffer; } This is basically identical code I wrote to ask the user for input, replace the character echo with asterisks, then print out the results. Here, though, I'm getting a function returns address of local variable warning for the return statement. So why am I getting no warnings from the other program, but trigger one for this code?

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• Netbeans, JPA Entity Beans in seperate projects. Unknown entity bean class

  - by Stu

  I am working in Netbeans and have my entity beans and web services in separate projects. I include the entity beans in the web services project however the ApplicaitonConfig.java file keeps getting over written and removing the entries I make for the entity beans in the associated jar file. My question is: is it required to have both the EntityBeans and the WebServices share the same project/jar file? If not what is the appropriate way to include the entity beans which are in the jar file? <?xml version="1.0" encoding="UTF-8"?> <persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"> <persistence-unit name="jdbc/emrPool" transaction-type="JTA"> <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider> <jta-data-source>jdbc/emrPool</jta-data-source> <exclude-unlisted-classes>false</exclude-unlisted-classes> <properties> <property name="eclipselink.ddl-generation" value="none"/> <property name="eclipselink.cache.shared.default" value="false"/> </properties> </persistence-unit> </persistence> Based on Melc's input i verified that that the transaction type is set to JTA and the jta-data-source is set to the value for the Glassfish JDBC Resource. Unfortunately the problem still persists. I have opened the WAR file and validated that the EntityBean.jar file is the latest version and is located in the WEB-INF/lib directory of the War file. I think it is tied to the fact that the entities are not being "registered" with the entity manager. However i do not know why they are not being registered.

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• HIbernate 3.5.1 - can I just drop in EHCache 2.0.1?

  - by caerphilly

  I'm using Hibernate 3.5.1, which comes with EHCache 1.5 bundled. If I want to use the latest EHCache release (2.0.1), is it just a matter of removing the ehcache-1.5.jar from my project, and replacing with ehcache-core-2.0.1.jar? Any issues to be aware of? Also - is a cache "region" in the Hibernate mapping file that same as a cache "name" in the ehcache configuration xml? What I want to do is define 2 named cache regions - one for read-only reference entities that won't change (lookup lists etc), and one for all other entities. So in ehcache I want to define two elements; <cache name="readonly"> ... </cache> <cache name="mutable"> ... </cache> And then in my Hibernate mapping files, I will specify the cache to be used for each entity: <hibernate-mapping> <class name="lookuplist"> <cache region="readonly" usage="read-only"/> <property> ... </property> </class> </hibernate-mapping> Will that work? Some of the documentation seems to imply that a separate region/cache gets created for each mapped class... Thanks.

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• Segmentation Fault

  - by Biranchi

  Hi All, I have the following piece of code for getting the hostname and IP address, #include <stdlib.h> #include <stdio.h> #include <netdb.h> /* This is the header file needed for gethostbyname() */ #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> int main(int argc, char *argv[]) { struct hostent *he; if (argc!=2){ printf("Usage: %s <hostname>\n",argv[0]); exit(-1); } if ((he=gethostbyname(argv[1]))==NULL){ printf("gethostbyname() error\n"); exit(-1); } printf("Hostname : %s\n",he->h_name); /* prints the hostname */ printf("IP Address: %s\n",inet_ntoa(*((struct in_addr *)he->h_addr))); /* prints IP address */ } but i am getting a warning and segmentation fault as host.c: In function ‘main’: host.c:24: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘int’ What is the error in the code ?? Thanks

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• Visual Studio 2010 is not allowing me to debug my code

  - by Tejs

  So, this interesting issue has been plaguing me for the past couple of hours. Visual Studio 2010 Ultimate no longer attaches the debugger and lets me debug my code. If I use the built in development server, then everything works fine. If I switch to Use Local IIS Web Server (http://localhost/), then all it does it attach to w3wp.exe, but no DLLs or PDBs are loaded for anything. I can go to Debug Windows Modules, and literally nothing is loaded in this window. Conversely, when using the built in development server, the Modules window displays all the DLLs and shows that the symbols for my DLLs have been loaded. Something is obviously amiss. The VS installation is completely bone stock. In IIS, my website is configured with ASP.NET 2.0 (because no 3.5 exists to select from the drop down), along with read / log visits / index this resource options checked on the "Home Directory" tab. Some of my failed ideas: 1) If I attach to process on the iexplore.exe instance where the website is displayed, it loads Internet Explorer's DLLs, but not mine. 2) I've restarted the computer multiple times 3) I've invoked devenv.exe /resetuserdata once 4) I've confirmed that every project is indeed set to debug and not release. 5) Deleted all \bin contents and rebuilt the solution. 6) Deleted entire solution and repulled from Source Control. Can someone tell me what is wrong with this thing? I'm going to have an aneurism from the headache this is causing me.

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• Flash browser game - HTTP + PHP vs Socket + Something else

  - by Maurycy Zarzycki

  I am developing a non-real time browser RPG game (think Kingdom of Loathing) which would be played from within a Flash app. At first I just wanted to make the communication with server using simply URLLoader to tell PHP what I am doing, and using $_SESSION to store data needed in-between request. I wonder if it wouldn't be better to base it on a socket connection, an app residing on a server written in Java or Python. The problem is I have never ever written such an app so I have no idea how much I'd have to "shift" my thoughts from simple responding do request (like PHP) to continuously working application. I won't hide I am also concerned about the memory and CPU usage of such Server app, when for example there would be hundreds of users connected. I've done some research. I have tried to do some research, but thanks to my nil knowledge on the sockets subject I haven't found anything helpful. So, considering the fact I don't need real time data exchange, will it be wise to develop the server side part as socket server, not in plain ol' PHP?

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• My method is too specific. How can I make it more generic?

  - by EricBoersma

  I have a class, the outline of which is basically listed below. import org.apache.commons.math.stat.Frequency; public class WebUsageLog { private Collection<LogLine> logLines; private Collection<Date> dates; WebUsageLog() { this.logLines = new ArrayList<LogLine>(); this.dates = new ArrayList<Date>(); } SortedMap<Double, String> getFrequencyOfVisitedSites() { SortedMap<Double, String> frequencyMap = new TreeMap<Double, String>(Collections.reverseOrder()); //we reverse order to sort from the highest percentage to the lowest. Collection<String> domains = new HashSet<String>(); Frequency freq = new Frequency(); for (LogLine line : this.logLines) { freq.addValue(line.getVisitedDomain()); domains.add(line.getVisitedDomain()); } for (String domain : domains) { frequencyMap.put(freq.getPct(domain), domain); } return frequencyMap; } } The intention of this application is to allow our Human Resources folks to be able to view Web Usage Logs we send to them. However, I'm sure that over time, I'd like to be able to offer the option to view not only the frequency of visited sites, but also other members of LogLine (things like the frequency of assigned categories, accessed types [text/html, img/jpeg, etc...] filter verdicts, and so on). Ideally, I'd like to avoid writing individual methods for compilation of data for each of those types, and they could each end up looking nearly identical to the getFrequencyOfVisitedSites() method. So, my question is twofold: first, can you see anywhere where this method should be improved, from a mechanical standpoint? And secondly, how would you make this method more generic, so that it might be able to handle an arbitrary set of data?

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• Best approach to cache Counts from SQL tables ?

  - by pixel3cs

  I would like to develop a Forum from scratch, with special needs and customization. I would like to prepare my forum for intensive usage and wondering how to cache things like User posts count and User replies count. Having only three tables, tblForum, tblForumTopics, tblForumReplies, what is the best approach of cache the User topics and replies counts ? Think at a simple scenario: user press a link and open the Replies.aspx?id=x&page=y page, and start reading replies. On the HTTP Request, the server will run an SQL command wich will fetch all replies for that page, also "inner joining with tblForumReplies to find out the number of User replies for each user that replied." select tblForumReplies.*, tblFR.TotalReplies from tblForumReplies inner join ( select IdRepliedBy, count(*) as TotalReplies from tblForumReplies group by IdRepliedBy ) as tblFR on tblFR.IdRepliedBy = tblForumReplies.IdRepliedBy Unfortunately this approach is very cpu intensive, and I would like to see your ideas of how to cache things like table Counts. If counting replies for each user on insert/delete, and store it in a separate field, how to syncronize with manual data changing. Suppose I will manually delete Replies from SQL.

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• How do I retrieve twitter xml for Flash site via php properly

  - by daidai

  Am I using TwitterScript to retrieve Twitter data for inside a Flash site. Due to Twitter's crossdomain policy, I need to setup a php proxy... Firstly I made a simple one <?php $url = $_GET['url']; readfile($url); ?> but I then get this error URL file-access is disabled in the server configuration which is only resolved by getting my host to turn fopen() on, which I don't want to do. Then I found this <?php function get_content($url) { $ch = curl_init(); curl_setopt ($ch, CURLOPT_URL, $url); curl_setopt ($ch, CURLOPT_HEADER, 0); ob_start(); curl_exec ($ch); curl_close ($ch); $string = ob_get_contents(); ob_end_clean(); return $string; } #usage: $url = $_GET['url']; $content = get_content ($url); var_dump ($content); ?> which solves that problem but the data now is the correct XML but looks like: string(39950) "<?xml version="1.0" encoding="UTF-8"?> <statuses type="array"> <status> ... </statuses>" How do I get the XML data out of that string?

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• OpenGL Pixel Format Attributes (NSOpenGLPixelFormatAttibutes) explanation?

  - by nacho4d

  Hi, I am not new to OpenGL, but not an expert. Many tutorials teach how to draw, 3D, 2D, projections, orthogonal, etc, but How about setting a the view? (NSOpenGLView in Cocoa, Macs). For example I have this: - (id) initWithFrame: (NSRect) frame { GLuint attribs[] = { //PF: PixelAttibutes NSOpenGLPFANoRecovery, NSOpenGLPFAWindow, NSOpenGLPFAAccelerated, NSOpenGLPFADoubleBuffer, NSOpenGLPFAColorSize, 24, NSOpenGLPFAAlphaSize, 8, NSOpenGLPFADepthSize, 24, NSOpenGLPFAStencilSize, 8, NSOpenGLPFAAccumSize, 0, 0 }; NSOpenGLPixelFormat* fmt = [[NSOpenGLPixelFormat alloc] initWithAttributes: (NSOpenGLPixelFormatAttribute*) attribs]; return self = [super initWithFrame:frame pixelFormat: [fmt autorelease]]; } And I don't understand very well their usage, specially when combining them. For example: If I want my view to be capable of full screen should I write NSOpenGLPFAFullScreen only ? or both? (by capable I mean not always in full screen) Regarding Double Buffer, what is this exactly? (Below: Apple's definition) If present, this attribute indicates that only double-buffered pixel formats are considered. Otherwise, only single-buffered pixel formats are considered Regarding Color: if NSOpenGLPFAColorSize is 24 and NSOpenGLPFAColorSize is 8 then it means that alpha and RGB components are treated differently? what happen if I set the former to 32 and the later to 0? Etc, etc,In general how do I learn to set my view from scratch? Thanks in advance. Ignacio.

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• Spring annotation-based container configuration context:include & exclude filters

  - by lisak

  Hey, first off I point to the similar question. I spent more than an hour to set this up, but PathMatchingResourcePatternResolver still scans everything. I have one common.xml (that is imported from specific.xml) and a specific.xml bean definition file. The context is loaded from specific.xml. In common.xml there is this element: <context:component-scan base-package="cz.instance.transl"> <context:exclude-filter type="aspectj" expression="cz.instance.transl.model..* &amp;&amp; cz.instance.transl.service..* &amp;&amp; cz.instance.transl.hooks..*"/> </context:component-scan> Where classes in packages like cz.instance.transl.service.* should not be subject of scanning, but everything else in here cz.instance.transl.* should be scanned through. But PathMatchingResourcePatternResolver marks everything as matching resources. It is the same with regex. BTW: in xml style configuration, one can have many components that share a common.xml beans via "import resource" when loading context. How this is done when Annotation-based container configuration is used ?

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• C++ RPC library suggestions

  - by Oxsnarder

  I'm looking for suggestions regarding RPC libraries implemented in C++, for C++ developers. Some requirements constraints: Should work on both linux/unix and win32 systems Be able to execute free function and class methods Hopefully written in modern C++ not 90's/java-esque C++ Be able to function over networks and hetrogenous architectures Not too slow or inefficient Hopefully provide interfaces for TR1 style std::function's et al. My example usage is to invoke the free function foo on a remote machine. ---snip--- // foo translation unit int foo(int i, int j) { return i + j; } ---snip--- ---snip--- // client side main int main() { //register foo on client and server //setup necassary connections and states int result; if (RPCmechanism.invoke("foo",4,9,result)) std::cout << "foo(4,9) = " result << std::endl; else std::cout << "failed to invoke foo(4,9)!" << std::endl; return 0; } ---snip--- Something that can achieve the above or similar would be great.

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• Method returns an IDisposable - Should I dispose of the result, even if it's not assigned to anythin

  - by mjd79

  This seems like a fairly straightforward question, but I couldn't find this particular use-case after some searching around. Suppose I have a simple method that, say, determines if a file is opened by some process. I can do this (not 100% correctly, but fairly well) with this: public bool IsOpen(string fileName) { try { File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None); } catch { // if an exception is thrown, the file must be opened by some other process return true; } } (obviously this isn't the best or even correct way to determine this - File.Open throws a number of different exceptions, all with different meanings, but it works for this example) Now the File.Open call returns a FileStream, and FileStream implements IDisposable. Normally we'd want to wrap the usage of any FileStream instantiations in a using block to make sure they're disposed of properly. But what happens in the case where we don't actually assign the return value to anything? Is it still necessary to dispose of the FileStream, like so: try { using (File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None)); { /* nop */ } } catch { return true; } Should I create a FileStream instance and dispose of that? try { using (FileStream fs = File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None)); } ... Or are these totally unnecessary? Can we simply call File.Open and not assign it to anything (first code example), and let the GC dispose of it right away?

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• log activity. intrusion detection. user event notification ( interraction ). messaging

  - by Julian Davchev

  Have three questions that I somehow find related so I put them in same place. Currently building relatively large LAMP system - making use of messaging(activeMQ) , memcache and other goodies. I wonder if there are best practices or nice tips and tricks on howto implement those. System is user aware - meaning all actions done can be bind to particular logged user. 1. How to log all actions/activities of users? So that stats/graphics might be extracted later for analysing. At best that will include all url calls, post data etc etc. Meaning tons of inserts. I am thinking sending messages to activeMQ and later cron dumping in DB and cron analysing might be good idea here. Since using Zend Framework I guess I may use some request plugin so I don't have to make the log() call all over the code. 2.How to log stuff so may be used for intrusion detection? I know most things might be done on http level using apache mods for example but there are also specific cases like (5 failed login attempts in a row (leads to captcha) etc etc..) This also would include tons of inserts. Here I guess direct usage of memcache might be best approach as data don't seem vital to be permanantly persisted. Not sure if cannot use data from point 1. 3.System will notify users of some events. Like need approval , something broke..whatever.Some events will need feedback(action) from user, others are just informational. Wonder if there is common solutions for needs like this. Example: Based on occuring event(s) user will be notifed (user inbox for example) what happend. There will be link or something to lead him to details of thingy that happend and take action accordingly. Those seem trivial at first look but problem I see if coding it directly is becoming really fast hard to maintain.

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• SharePoint Lists.asmx's UpdateListItems() returns too much data

  - by Philipp Schmid

  Is there a way to prevent the UpdateListItems() web service call in SharePoint's Lists.asmx endpoint from returning all of the fields of the newly created or updated list item? In our case an event handler attached to our custom list is adding some rather large field values which are turned to the client unnecessarily. Is there a way to tell it to only return the ID of the newly created (or updated) list item? For example, currently the web service returns something like this: <Results xmlns="http://schemas.microsoft.com/sharepoint/soap/"> <Result ID="1,Update"> <ErrorCode>0x00000000</ErrorCode> <z:row ows_ID="4" ows_Title="Title" ows_Modified="2003-06-19 20:31:21" ows_Created="2003-06-18 10:15:58" ows_Author="3;#User1_Display_Name" ows_Editor="7;#User2_Display_Name" ows_owshiddenversion="3" ows_Attachments="-1" ows__ModerationStatus="0" ows_LinkTitleNoMenu="Title" ows_LinkTitle="Title" ows_SelectTitle="4" ows_Order="400.000000000000" ows_GUID="{4962F024-BBA5-4A0B-9EC1-641B731ABFED}" ows_DateColumn="2003-09-04 00:00:00" ows_NumberColumn="791.00000000000000" xmlns:z="#RowsetSchema" /> </Result> ... </Results> where as I am looking for a trimmed response only containing for example the ows_ID attribute: <Results xmlns="http://schemas.microsoft.com/sharepoint/soap/"> <Result ID="1,Update"> <ErrorCode>0x00000000</ErrorCode> <z:row ows_ID="4" /> </Result> ... </Results> I have unsuccessfully looked for a resource that documents all of the valid attributes for both the <Batch> and <Method> tags in he updates XmlNode parameter of UpdateListItems() in the hope that I will find a way to specify the fields to return. A solution for WSS 3.0 would be preferable over an SP 2010-only solution.

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• Custom API requirement

  - by Jonathan.Peppers

  We are currently working on an API for an existing system. It basically wraps some web-requests as an easy-to-use library that 3rd party companies should be able to use with our product. As part of the API, there is an event mechanism where the server can call back to the client via a constantly-running socket connection. To minimize load on the server, we want to only have one connection per computer. Currently there is a socket open per process, and that could eventually cause load problems if you had multiple applications using the API. So my question is: if we want to deploy our API as a single standalone assembly, what is the best way to fix our problem? A couple options we thought of: Write an out of process COM object (don't know if that works in .Net) Include a second exe file that would be required for events, it would have to single-instance itself, and open a named pipe or something to communicate through multiple processes Extract this exe file from an embedded resource and execute it None of those really seem ideal. Any better ideas?

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• Minimizing server load in case of many XMLHttpRequest calls

  - by user1888975

  I am making a website where users are to like some articles. Whenever the like button is clicked I am sending a XMLHttpRequest to the server to run a file called like_clicked.php along with the get data of article id and user id. This file takes article id and user id and updates the sql database and also adds a node in an xml file related to the user. This is the first time I am doing something for mass usage. I am worried about the server load when too many users call the like_clicked.php file. Please help me, if this method is ok. I am also thinking of an alternative in case the above method fails. I am thinking of making many like_clicked files (namely like_clicked1.php, like_clicked2.php ... ) to minimize load on a single i-node. Is there a method to detect that it is better to call the next like_clicked file. Here we would need to detect how many calls per unit time are coming for the particular file. How do we handle this? Thanks in advance.

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• Transferring HashMap between client and server using Sockets (JAVA)

  - by sar

  I am working on a JAVA project in which there are multiple terminals. These terminals act as client and servers. For example if there are 3 terminals A,B and C.Then at any given point in time one of them say A, will be a client making broadcast request. The other two terminals, B and C, will reply. I am using sockets to make them communicate. Once the reply is received from all the other terminals A will check the pool of channels to see if any one of the channel is free. It takes up the free channel and making it availabilty false. The channelpool is implemented using HashMAp: HashMap channelpool = new HashMap(); channelpool = 1=true, 2=true, 3=false, 4=true, 5=true, 6=true, 7=true, 8=true, 9=true, 10=true So initially all the channels are true, any terminal can take any channel. But once the channel is taken it is set to false for the period of use and then reset to true. Now this Hashmap has to be shared among the distributed terminals. Also it should be kept up to date. I can not used a shared resource among the terminals to store the HashMap.Can someone tell me an easy way to transfer the HashMap between the terminals. I will appreciate if someone could point me to a website which discusses this.

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• How to avoid concurrent execution of a time-consuming task without blocking?

  - by Diego V

  I want to efficiently avoid concurrent execution of a time-consuming task in a heavily multi-threaded environment without making threads wait for a lock when another thread is already running the task. Instead, in that scenario, I want them to gracefully fail (i.e. skip its attempt to execute the task) as fast as possible. To illustrate the idea considerer this unsafe (has race condition!) code: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing running = true; try { runExpensiveTask(); } finally { running = false; } } I though about using a variation of Double-Checked Locking (consider that running is a primitive 32-bit field, hence atomic, it could work fine even for Java below 5 without the need of volatile). It could look like this: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing synchronized (ThisClass.class) { if (running) return; running = true; try { runExpensiveTask(); } finally { running = false; } } } Maybe I should also use a local copy of the field as well (not sure now, please tell me). But then I realized that anyway I will end with an inner synchronization block, that still could hold a thread with the right timing at monitor entrance until the original executor leaves the critical section (I know the odds usually are minimal but in this case we are thinking in several threads competing for this long-running resource). So, could you think in a better approach?

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• refactoring my code. My headers (Header Guard Issues)

  - by numerical25

  I had a post similar to this awhile ago based on a error I was getting. I was able to fix it but since then I been having trouble doing things because headers keep blocking other headers from using code. Honestly, these headers are confusing me and if anyone has any resources that will address these types of issues, that will be helpful. What I essentially want to do is be able to have rModel.h be included inside RenderEngine.h. every time I add rModel.h to RenderEngine.h, rModel.h is no longer able to use RenderEngine.h. (rModel.h has a #include of RenderEngine.h as well). So in a nutshell, RenderEngine and rModel need to use each others functionalities. On top of all this confusion, the Main.cpp needs to use RenderEngine. stdafx.h #include "targetver.h" #define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows headers // Windows Header Files: #include <windows.h> // C RunTime Header Files #include <stdlib.h> #include <malloc.h> #include <memory.h> #include <tchar.h> #include "resource.h" main.cpp #include "stdafx.h" #include "RenderEngine.h" #include "rModel.h" // Global Variables: RenderEngine go; rModel *g_pModel; ...code........... rModel.h #ifndef _MODEL_H #define _MODEL_H #include "stdafx.h" #include <vector> #include <string> #include "rTri.h" #include "RenderEngine.h" ........Code RenderEngine.h #pragma once #include "stdafx.h" #include "d3d10.h" #include "d3dx10.h" #include "dinput.h" #include "rModel.h" .......Code......

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• Whether to put method code in a VB.Net data storage class, or put it in a separate class?

  - by Alan K

  TLDR summary: (a) Should I include (lengthy) method code in classes which may spawn multiple objects at runtime, (b) does doing so cause memory usage bloat, (c) if so should I "outsource" the code to a class that is loaded only once and have the class methods call that, or alternatively (d) does the code get loaded only once with the object definition anyway and I'm worrying about nothing? ........ I don't know whether there's a good answer to this but if there is I haven't found it yet by searching in the usual places. In my VB.Net (2010 if it matters) WinForms project I have about a dozen or so class objects in an object model. Some of these are pretty simple and do little more than act as data storage repositories. The ones further up the object model, however, have an increasing number of methods. There can be a significant number of higher level objects in use though the exact number will be runtime dependent so I can't be more precise than that. As I was writing the method code for one of the top level ones I noticed that it was starting to get quite lengthy. Memory optimisation is something of a lost art given how much memory the average PC has these days but I don't want to make my application a resource hog. So my questions for anyone who knows .Net way better than I do (of which there will be many) are: Is the code loaded into memory with each instance of the class that's created? Alternatively is it loaded only once with the definition of the class, and all derived objects just refer to that definition? (I'm not really sure how that could be possible given that, for example, event handlers can be assigned dynamically, but no harm asking.) If the answer to the first one is yes, would it be more efficient to write the code in a "utility" object which is loaded only once and called from the real class' methods? Any thoughts appreciated.

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