spring - Connecting multiple flex clients to a single java class -


i have multi-user application consisting of flex client , blazeds/spring/java backend - have main elements working fine ie. sending messages destination, consuming , producing. flex clients able send , retrieve string class no problem. want have 2 clients access same variable..in crude sample i'm sending guid each swf append string _players server side. happens when launch swf a, recieves guid fine, swf b. swf recieves guid swf b, swf b not recieve swf a. btw same swf code launched twice each in different browser.

can see i'm going wrong or might better solution?

public class gamefeed {      private static ganefeedthread thread;      private final messagetemplate template;      public gamefeed(messagetemplate template) {         this.template = template;     }      public void start() {         if (thread == null) {             thread = new ganefeedthread(this.template);             thread.start();         }     }      public void stop() {         thread.running = false;         thread = null;     }      public static class ganefeedthread extends thread {          public boolean running = false;          private final messagetemplate template;          public ganefeedthread(messagetemplate template) {             this.template = template;         }          private static string _players;          public void addplayer(string name)         {             _players += name + ",";         }         while (this.running) {                   this.template.send("game-feed", _players);          }

you have threading problem in class. not sure if cause of problem - could.

it seams sharing data though _player variable. variable not thread safe. has 2 major problem:

  • issue 1 : if 2 clients invoke addplayer method @ same time - not clear happen player variable - alt least have lost update
  • issue 2: (this maybe cause) - java memory model not guarantee _player variable updated in both threads without proper concurrency management.

to fix have 2 things:

  • first: wrap _players += name + ","; in synchronized block (for issue 1)
  • second: mark _players volatile (for issue 2)

@see http://jeremymanson.blogspot.com/2008/11/what-volatile-means-in-java.html


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