How to Monitor an existing Java class with JMX?

Question

I have an existing Java class as follows and I want to monitor number of method invocations for each method in this class using JMX. How do I do it? I tried google but I can't see the big picture on how the whole thing is connected. It would be great if I can see see some code examples

Public class RPCServer {

   public void storeSchema() { // want to count number of method invocations
       System.out.println("storeSchema");
   }

   public void getSchema() { // want to count number of method invocations
       System.out.println("getSchema");
   }

   public void storeRow() { // want to count number of method invocations
       System.out.println("storeRow");
   }

   public void getRow() {  //want to count number of method invocations
       System.out.println("getRow");
   }

} 

Answer 1

I you want to see how many time some methods are executed through JMX, I propose this solution

First you need an interface for your class. Only the methods of this interface are visible for JMX:

public interface RPCServerInterface {
  int countMethodInvocation(String method);
}

Then in the class you store how many time each function is call.

public class RPCServer implements RPCServerInterface{
  private int row;
  private Map<String,Integer> countByMethod = new HashMap<String,Integer>();

  // +1 to the number of time of execution of this method
  private void sumMethodInvocation(String method) {
   if ( countByMethod.containsKey(method) ) {
     int n = countByMethod.get(method);
     countByMethod.put(method, n+1);
   } else {
     countByMethod.put(method,1);
   }
  }

  // how many time the method has been invoked 
  @Override
  public int countMethodInvocation(String method){
    return countByMethod.containsKey(method)?countByMethod.get(method):0;
  }

  public void setRow(int i) { 
    // register each time is executed
    this.sumMethodInvocation("setRow"); 
    this.row = i;
  }
  public int getRow() {
    // register each time is executed
    this.sumMethodInvocation("getRow");
    return row;
  }
}}
} 

Then you have to register your Bean:

MBeanServer mBeanServer = ManagementFactory.getPlatformMBeanServer();
RPCServer rpcServer =  new RPCServer();
ObjectName objectName = new ObjectName("org.foo.RPCServer.jmx:type=RPCServerInterface");

StandardMBean standardMBean = new StandardMBean(rpcServer,RPCServerInterface.class);
mBeanServer.registerMBean(standardMBean, objectName);

The path org.foo.RPCServer.jmx is arbitrary.

Then your run jconsole and you find the process you are running.

Then you can run the command countMethodInvocation and you can get the number of execution time.

Like this:

This tutorial can be useful:

what-is-jmx-mbean-jconsole-tutorial