Request java heap dump (core dump) from within application

Question

I need a way to request a heap dump from within the application.

Rationale: When I encounter a specific error condition, I'd like to dump heap, so that I can see what is holding on to the memory.

But I would like to automate this (For example, when I detect that some specific condition has occurred. Or when a watchdog doesn't gets its pings anymore. When some test fails). Thus I need a way to dump the heap from within the application itself. I can't seem to find it with the MX beans stuff. Although the MX Beans can give very nice stack traces with monitor and "ownable synchronizer" info, deadlock and contention info, I can't seem to find a way to request a heap dump. Are there any such way? Or by some indirect means, for example how does these JVisualVM things do it? And one can tell the JVM to dump core on OutOfMemoryExceptions..?

Answer 1

If it's not enough to use the -XX:HeapDumpOnOutOfMemoryError command line argument to dump heap on OutOfMemoryError, there's a HotSpot-specific way of programmatically dumping heap from Java applications:

MBeanServer mBeanServer = ManagementFactory.getPlatformMBeanServer();
String dumpFilePath = "./banana.hprof";
HotSpotDiagnosticMXBean hotSpotDiagnosticMXBean = ManagementFactory.newPlatformMXBeanProxy(
    mBeanServer,
    "com.sun.management:type=HotSpotDiagnostic",
    HotSpotDiagnosticMXBean.class);
hotSpotDiagnosticMXBean.dumpHeap(dumpFilePath, true);