Question

I have a problem about the mbeans. I have created a simple mbean and I have registered it on the default mBeanServer that is run (Via eclipse or java -jar mbean.jar) and in the same process if I try to fouund the mbean registered with a simple query:

for (ObjectInstance instance : mbs.queryMBeans(ObjectNameMbean, null)) {
    System.out.println(instance.toString());
}

the query retuerns my mbean, but if I start another process and try to search this mbean registered the mbeas is not found! why?

The approch is : (Process that is running)

public static void main(String[] args) throws Exception
{
    MBeanServer mbeanServer =ManagementFactory.getPlatformMBeanServer(); 
    ObjectName objectName = new ObjectName(ObjectNameMbean);
    Simple simple = new Simple (1, 0);
    mbeanServer.registerMBean(simple, objectName);
    while (true)
    {
       wait (Is this necessary?)
    }
}

So this is the first process that is running (that has the only pourpose to registry the mbean, because there is another process that want to read these informations.
So I start another process to search this mbean but nothing.
I ‘m not using jboss but the local Java virtual Machine but my scope is to deploy this simple application in one ejb (autostart) and another ejb will read all informations.
All suggestions are really apprecciated.

This example should be more useful :

Object Hello:

public class Hello implements HelloMBean { 
    public void sayHello() { 
    System.out.println("hello, world"); 
    } 

    public int add(int x, int y) { 
    return x + y; 
    } 

    public String getName() { 
    return this.name; 
    } 


    public int getCacheSize() { 
    return this.cacheSize; 
    } 

    public synchronized void setCacheSize(int size) { 
    this.cacheSize = size; 

    System.out.println("Cache size now " + this.cacheSize); 
    } 

    private final String name = "Reginald"; 
    private int cacheSize = DEFAULT_CACHE_SIZE; 
    private static final int DEFAULT_CACHE_SIZE = 200; 
} 

Interface HelloBean (implemented by Hello)

public interface HelloMBean { 

    public void sayHello(); 
    public int add(int x, int y); 

    public String getName(); 

    public int getCacheSize(); 
    public void setCacheSize(int size); 
} 

Simple Main

import java.lang.management.ManagementFactory;
import java.util.logging.Logger;

import javax.management.MBeanServer;
import javax.management.ObjectName;

public class Main { 


    static Logger aLog = Logger.getLogger("MBeanTest");

    public static void main(String[] args)  {

        try{

            MBeanServer mbs = ManagementFactory.getPlatformMBeanServer(); 

            ObjectName name = new ObjectName("ApplicationDomain:type=Hello"); 

            Hello mbean = new Hello(); 

            mbs.registerMBean(mbean, name); 

            //      System.out.println(mbs.getAttribute(name, "Name"));
            aLog.info("Waiting forever..."); 
            Thread.sleep(Long.MAX_VALUE);
        }
        catch(Exception x){
            x.printStackTrace();
            aLog.info("exception");
        }
    } 
} 

So now I have exported this project as jar file and run it as “java -jar helloBean.jar” and by eclipse I have modified the main class to read informations of this read (Example “Name” attribute) by using the same objectname used to registry it .

Main to read :

public static void main(String[] args)  {

    try{

        MBeanServer mbs = ManagementFactory.getPlatformMBeanServer(); 

        ObjectName name = new ObjectName("ApplicationDomain:type=Hello"); 

        System.out.println(mbs.getAttribute(name, "Name"));

    }
    catch(Exception x){
        x.printStackTrace();
        aLog.info("exception");
    }
} 

But nothing, the bean is not found.

Project link : here!

Any idea?

Answer 1

I suspect the issue here is that you have multiple MBeanServer instances. You did not mention how you acquired the MBeanServer in each case, but in your second code sample, you are creating a new MBeanServer instance which may not be the same instance that other threads are reading from. (I assume this is all in one JVM…)

If you are using the platform agent, I recommend you acquire the MBeanServer using the ManagementFactory as follows:

MBeanServer mbs = java.lang.management.ManagementFactory.getPlatformMBeanServer() ;

That way, you will always get the same MBeanServer instance.