How to debug applet if there are two JVMs started?

Question

I need to debug an applet which is started by another java application(webstart) by opening the browser window. It was working fine with older versions of java, but with Java 1.7_45, the debug works only for the first JVM(which is the webstart application).

I use these parameters in the jcontrol:

-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8086

I think there's nothing wrong with this, because the debugger attaches correctly. The only problem is, I can only debug the webstart application and not the applet which is run after that.

In the console of both the webstart application and the applet shows this:

Java Plug-in 10.45.2.18
Using JRE version
1.7.0_45-b18 Java HotSpot(TM) 64-Bit Server VM

The JNLP java process starts with the agentlib options I set in the jcontrol:

/usr/lib/jvm/java-7-oracle/jre/bin/java -Xmx512m -Xms128m 
-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8086 
-Xbootclasspath/a:/usr/lib/jvm/java-7-oracle/jre/lib/javaws.jar:/usr/lib/jvm/java-7-oracle/jre/lib/deploy.jar:/usr/lib/jvm/java-7-oracle/jre/lib/plugin.jar 
-classpath /usr/lib/jvm/java-7-oracle/jre/lib/deploy.jar 
-Djnlpx.vmargs="-Xmx512m -Xms128m 
-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=8086" 
-Djnlpx.jvm=/usr/lib/jvm/java-7-oracle/jre/bin/java
....

When I open an applet I want to debug from this webstart app, new tab in firefox is opened and three processes are started:

/opt/firefox/plugin-container /usr/lib/jvm/java-7-oracle/jre/lib/amd64/libnpjp2.so -greomni /opt/firefox/omni.ja -appomni /opt/firefox/browser/omni.ja -appdir /opt/firefox/browser 13665 true plugin

/usr/lib/jvm/java-7-oracle/jre/bin/java -D__jvm_launched=8315888593 -D__applet_launched=8315738716 -Xbootclasspath/a:/usr/lib/jvm/java-7-oracle/jre/lib/deploy.jar:/usr/lib/jvm/java-7-oracle/jre/lib/javaws.jar:/usr/lib/jvm/java-7-oracle/jre/lib/plugin.jar -Djava.class.path=/usr/lib/jvm/java-7-oracle/jre/classes -Dsun.awt.warmup=true sun.plugin2.main.client.PluginMain write_pipe_name=/tmp/.com.sun.deploy.net.socket.13900.6946726655044877700.AF_UNIX

/usr/lib/jvm/java-7-oracle/jre/bin/java -D__jvm_launched=8317712180 -D__applet_launched=8315738716 -Xbootclasspath/a:/usr/lib/jvm/java-7-oracle/jre/lib/deploy.jar:/usr/lib/jvm/java-7-oracle/jre/lib/javaws.jar:/usr/lib/jvm/java-7-oracle/jre/lib/plugin.jar -Djava.class.path=/usr/lib/jvm/java-7-oracle/jre/classes -Djnlpx.session.data=/tmp/session6916520025949955515 -Dsun.awt.warmup=true sun.plugin2.main.client.PluginMain write_pipe_name=/tmp/.com.sun.deploy.net.socket.13900.3102318208570708149.AF_UNIX

As you can see, the debug port is not passed as a parameter to commands executing applet

I've tried to add new debug parameters to the applet tag(I've tried both Xdebug and agentlib), but it does nothing:

<param name="java_arguments" value="-Djnlp.packEnabled=true -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8087">

I've also tried to use appletviewer and after resolving problems with pack200 libraries, I'm stuck on this exception:

java.lang.NoClassDefFoundError: netscape/javascript/JSException
at java.lang.Class.getDeclaredConstructors0(Native Method)

But I wouldn't consider this as a solution because appletviewer doesn't work with pack200 and I'd have to add duplicate libraries to the server.

Is it somehow possible to:

1. Define separate jdwp ports for webstart app and plugins?
2. Listen on the same port for both?
3. Choose for which one the debug will be used?

I use 64 bit oracle JDK 1.7.0_45-b18 and 64 bit Firefox on Linux.

Answer 1

Not really a solution, but there's a workaround for my problem.

• Clear the java parameters in jcontrol
• Start the webstart application
• Add the java parameters again
• Run applet

After that, the parameters are passed to applet only and debug works.