Installing JAD on Eclipse

GREAT instructions are here http://jadclipse.sourceforge.net/wiki/index.php/Main_Page

.... more to come...

Since I am behind corporate proxy, Eclipse Marketplace is blocked (as usual....)... so I had to download the jar and put in in ECLIPSE_HOME\plugin folder... and restart Eclipse.

In Eclipse, check that JadClipse menu appears in Windows/Preferences/Java. Remember to set path to jad (you will have to download it separately).

Java Mission Control, the Swiss Knife of Monitoring

I have extensively used JRockit Mission Control and really missed when I moved to Sun-JVM projects.... now that we use WebLogic 12 we have Java 1.7 (> u40) and so we can use Java Mission Control (JMC), which is exactly like the JRockit version..... with its fantastic Flight Recorder...

Awesome presentation here ( a bit blabla in the first few minutes.... just be patient...)


Here the code used in the example:

package com.pierre;

public class DeadlockGenerator {
    private static class AllocThread extends Thread {
 public void run() {
     while (true) {
  Thread.yield();
  try {
      sleep(20 * 1000);
  } catch (Exception e) {

  }
  for (int i = 0; i < 40000; i++) {
      char[] tmp = new char[1024 * 1024];
      tmp[1] = 'a';
  }
     }
 }
    }

    private static class LockerThread extends Thread {
 Object l1;
 Object l2;

 public void init(Object lock1, Object lock2) {
     l1 = lock1;
     l2 = lock2;
 }

 public void run() {
     while (true) {
  synchronized (l1) {
      try {
   Thread.sleep(1000);
      } catch (InterruptedException e) {
      }
      ;
  }
  synchronized (l2) {
      try {
   Thread.sleep(1000);
      } catch (InterruptedException e) {
      }
      ;
  }
  System.out.println("Got one!");
     }
 }
    }

    public static void main(String[] args) {
 AllocThread allocThread = new AllocThread();
 Object lock1 = new Object();
 Object lock2 = new Object();
 LockerThread first = new LockerThread();
 LockerThread second = new LockerThread();
 first.init(lock1, lock2);
 second.init(lock2, lock1);
 allocThread.start();
 first.start();
 second.start();

    }
}

This video is much shorter and at the end it shows how to solve locking issues

monitoring remotely with jvisualvm and jstatd

If you run jstatd on a machine, you will get:

could not create remote object
access denied ("java.util.PropertyPermission" "java.rmi.server.ignoreSubClasses" "write")
java.security.AccessControlException: access denied ("java.util.PropertyPermission" "java.rmi.server.ignoreSubClasses" "write")
        at java.security.AccessControlContext.checkPermission(AccessControlContext.java:372)
        at java.security.AccessController.checkPermission(AccessController.java:559)
        at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
        at java.lang.System.setProperty(System.java:783)
        at sun.tools.jstatd.Jstatd.main(Jstatd.java:139)

So, create a jstatd.policy file and enter:

grant codebase "file:D:/pierre/Java/jdk1.7.0_79/lib/tools.jar" {
permission java.security.AllPermission;
};

(full documentation of policy files here )

then run "jstatd -J-Djava.security.policy=jstatd.policy"

Now in jvisualvm you can add remote host, then right-click on the host, "add jstatd connection" and this will connect to the default 1099 port on remote host (it's a RMI server, so it uses the default RMI port)

use "jps " from your local machine to check that the jstatd is actually reachable.

See also http://www.nljug.org/nieuws/blog-profiling-remote-jvm-using-visualvm/ for a more complete list of options. Particularly useful the -p option and the -J-Djava.rmi.server.hostname=x.x.x.x .