Programmatic deadlock detection in java

You can do this programmatically using the ThreadMXBean that ships with the JDK:

ThreadMXBean bean = ManagementFactory.getThreadMXBean();long[] threadIds = bean.findDeadlockedThreads(); // Returns null if no threads are deadlocked.if (threadIds != null) {    ThreadInfo[] infos = bean.getThreadInfo(threadIds);    for (ThreadInfo info : infos) {        StackTraceElement[] stack = info.getStackTrace();        // Log or store stack trace information.    }}

Obviously you should try to isolate whichever thread is performing this deadlock check - Otherwise if that thread deadlocks it won't be able to run the check!

Incidentally this is what JConsole is using under the covers.

One useful hint for investigation:

If you can catch the application red handed and suspect a deadlock has occurred, go and press "Ctrl-Break" in the java.exe console window (or "Ctrl-\" on Solaris/Linux).The jvm will dump the current status and stack trace of all threads, find out dead locks and precisely describe them.

It will look something like this:

Full thread dump Java HotSpot(TM) Client VM (1.5.0_09-b03 mixed mode):"[Test Timer] Request Queue" prio=6 tid=0x13d708d0 nid=0x1ec in Object.    wait() [0x1b00f000..0x1b00fb68]    at java.lang.Object.wait(Native Method)    at java.lang.Object.wait(Unknown Source)    at library.util.AsyncQueue.run(AsyncQueue.java:138)        - locked <0x02e70000> (a test.server.scheduler.SchedulerRequestQueue)    ...Found one Java-level deadlock:============================="Corba service":  waiting to lock monitor 0x13c06684 (object 0x04697d90, a java.lang.Object),  which is held by "[Server Connection] Heartbeat Timer""[Server Connection] Heartbeat Timer":  waiting to lock monitor 0x13c065c4 (object 0x0467e728, a test.proxy.ServerProxy), which is held by "Corba service"Java stack information for the threads listed above:==================================================="Corba service":    at test.proxy.ServerProxy.stopHBWatchDog(ServerProxy:695)    - waiting to lock <0x04697d90> (a java.lang.Object)    ...

You can detect the deadlocked threads programmatically using ThreadMXBean class.Here is the code,

    ThreadMXBean bean = ManagementFactory.getThreadMXBean();    long ids[] = bean.findMonitorDeadlockedThreads();    if(ids != null)    {        ThreadInfo threadInfo[] = bean.getThreadInfo(ids);        for (ThreadInfo threadInfo1 : threadInfo)        {            System.out.println(threadInfo1.getThreadId());    //Prints the ID of deadlocked thread            System.out.println(threadInfo1.getThreadName());  //Prints the name of deadlocked thread            System.out.println(threadInfo1.getLockName());    //Prints the string representation of an object for which thread has entered into deadlock.            System.out.println(threadInfo1.getLockOwnerId());  //Prints the ID of thread which currently owns the object lock            System.out.println(threadInfo1.getLockOwnerName());  //Prints name of the thread which currently owns the object lock.        }    }    else    {        System.out.println("No Deadlocked Threads");    }

Click here for more info on how to detect the deadlocked threads.