Attaching to the J9VM using the Attach API

Question

What is the correct way to attach to IBM's J9VM using the Java Attach API?

I am trying the following (with having the JDK's tools.jar in my classpath):

private static final J9AttachProvider ATTACH_PROVIDER = new J9AttachProvider();


...snip...
        String pid = getPIDofRunningVM();
        Constructor<J9VirtualMachine> constructor = J9VirtualMachine.class.getConstructor(new Class[]{AttachProvider.class, String.class
                });
        constructor.setAccessible(true);
        J9VirtualMachine virtualMachine = constructor.newInstance(new Object[]{ATTACH_PROVIDER, pid});

I also tried doing it without the use of reflection but i keep getting

Exception in thread "main" java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:44)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:516)
    at de.test.Test.gogo(Test.java:34)
    at de.teset.Test.main(Test.java:26)
Caused by: java.lang.IllegalAccessError
    at ibm.tools.attach.J9VirtualMachine.<init>(J9VirtualMachine.java:24)
    ... 6 more

Does anybody know what the proper way to do this is?

score 2 · Answer 1 · answered Nov 21 '12 at 21:34

see the "//IBM" part inside

     private static final String CONNECTOR_ADDRESS =
     "com.sun.management.jmxremote.localConnectorAddress";

void retrieveSomeMXBean (String pid) throws Exception {
    com.sun.tools.attach.VirtualMachine vm =
            com.sun.tools.attach.VirtualMachine
            .attach(pid);
    String connectorAddress = vm.getAgentProperties().getProperty(
            CONNECTOR_ADDRESS);


    if (connectorAddress == null) {
        String agent = vm.getSystemProperties().getProperty("java.home")
                + File.separator + "lib" + File.separator
                + "management-agent.jar";
        vm.loadAgent(agent);

        connectorAddress = vm.getAgentProperties().getProperty(
                CONNECTOR_ADDRESS);
    }

    // IBM
    if (connectorAddress == null) {

        String agent = "instrument,"
                + vm.getSystemProperties().getProperty("java.home")
                + File.separator + "lib" + File.separator
                + "management-agent.jar=";
        vm.loadAgentLibrary(agent);

        connectorAddress = vm.getSystemProperties().getProperty(
                CONNECTOR_ADDRESS);
    }

    JMXServiceURL url = new JMXServiceURL(connectorAddress);
    JMXConnector connector = JMXConnectorFactory.connect(url);
    mbeanConn = connector.getMBeanServerConnection();

    memoryMXBean = new ObjectName("java.lang:type=Memory");

}

a couple of bugs that escaped into the code: 1. before instrumenting the IBM vm, one must test for the existence of the agent: i.e. insert this check before the line marked with //IBM if(null==connectorAddress) { (connectorAddress = vm.getSystemProperties().getProperty( CONNECTOR_ADDRESS)); } 2. the connector (JMXConnector connector...) retrieved from the JMXConnectorFactory must be closed when the mbean is no longer needed. so in this case the connector should be a member in the class to enable connector.close() later on. — nati ashush, Nov 22 '12 at 17:28

Attaching to the J9VM using the Attach API

1 Answers1