RFC: Netx - Set JNLPClassloader as the classloader for system created threads

[Deepak Bhole]

* Omair Majid <omajid at redhat.com> [2009-07-09 11:58]:
> Hi,
>
> The attached patch makes JNLPClassLoader the context classloader for  
> threads created before the JNLP application starts. This deals with the  
> case where the JNLP application needs a previously created thread (such  
> as the Swing Event Dispatch Thread) to load a resource provided by the  
> application.
>
> Bugs:
> https://bugzilla.redhat.com/show_bug.cgi?id=509301
> http://kenai.com/jira/browse/TRIDENT-1?focusedCommentId=15776&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_15776
>
>
> ChangeLog:
> 2009-07-09  Omair Majid <omajid at redhat.com>
>
>   * rt/net/sourceforge/jnlp/Launcher.java
>   (launchApplication): Call setContextClassLoaderForAllThreads.
>   (setContextClassLoaderForAllThreads): New function.
>
> Any comments?
>
> Cheers,
> Omair

> diff -r b4bb02c70835 rt/net/sourceforge/jnlp/Launcher.java
> --- a/rt/net/sourceforge/jnlp/Launcher.java	Tue Jul 07 13:44:35 2009 -0400
> +++ b/rt/net/sourceforge/jnlp/Launcher.java	Thu Jul 09 11:16:04 2009 -0400
> @@ -23,6 +23,8 @@
>  import java.io.File;
>  import java.io.IOException;
>  import java.io.InputStream;
> +import java.lang.management.ManagementFactory;
> +import java.lang.management.ThreadMXBean;
>  import java.lang.reflect.Method;
>  import java.net.URL;
>  import java.util.LinkedList;
> @@ -425,8 +427,7 @@
>              Method main = mainClass.getDeclaredMethod("main", new Class[] {String[].class} );
>              String args[] = file.getApplication().getArguments();
>  
> -            // required to make some apps work right
> -            Thread.currentThread().setContextClassLoader(app.getClassLoader());
> +            setContextClassLoaderForAllThreads(app.getClassLoader());
>  
>              if (splashScreen != null) {
>                  if (splashScreen.isSplashScreenValid()) {
> @@ -447,6 +448,45 @@
>          }
>      }
>  
> +    /**
> +     * Set the classloader as the context classloader for all threads. This is
> +     * required to make some applications work. For example, an application that
> +     * provides a custom Swing LnF may ask the swing thread to load resources
> +     * from their JNLP, which would only work if the Swing thread knows about
> +     * the JNLPClassLoader.
> +     * 
> +     * @param classLoader the classloader to set as the context classloader
> +     */
> +    private void setContextClassLoaderForAllThreads(ClassLoader classLoader) {
> +        ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
> +        ThreadGroup root;
> +        
> +        root = Thread.currentThread().getThreadGroup();
> +        while (root.getParent() != null) {
> +            root = root.getParent();
> +        }
> +
> +        /* be prepared for change in thread size */
> +        int threadCountGuess = threadBean.getThreadCount();
> +        Thread[] threads;
> +        do {
> +            threadCountGuess = threadCountGuess * 2;
> +            threads = new Thread[threadCountGuess];
> +            root.enumerate(threads, true);
> +        } while (threads[threadCountGuess-1] != null);
> +        
> +        
> +        for (Thread thread: threads) {
> +            if (thread != null) {
> +                if (JNLPRuntime.isDebug()) {
> +                    System.err.println("Setting " + classLoader + " as the classloader for thread " + thread.getName());
> +                }
> +                thread.setContextClassLoader(classLoader);
> +            }
> +        }
> +        
> +    }
> +


Assuming you have tested this, go ahead and apply.

Deepak

>      /** 
>       * Launches a JNLP applet. This method should be called from a
>       * thread in the application's thread group.<p>