JMX, SNMP, Java, etc...

    
/*
 * InstanceOfExample.java
 *
 * Created on March 14, 2007, 4:40 PM
 *
 * SCCS: %W%
 * Copyright (c) Sun Microsystems, 2007 - All rights reserved.
 */

package instanceofpkg;

import java.lang.management.ManagementFactory;
import java.util.logging.Logger;
import javax.management.MBeanServer;
import javax.management.ObjectName;
import javax.management.Query;
import javax.management.StandardMBean;

/**
 * Class InstanceOfExample
 * @author Sun Microsystems, 2005 - All rights reserved.
 */
public class InstanceOfExample {
    
    /**
     * A logger for this class.
     **/
    private static final Logger LOG =
            Logger.getLogger(InstanceOfExample.class.getName());
    
    /** Creates a new instance of InstanceOf */
    public InstanceOfExample() {
    }
    
    // ---------------------------------------------------------
    // A Wombat MBean...
    //
    public static interface WombatMBean {
        public String getDescription();
    }
    public static class Wombat implements WombatMBean {
        public String getDescription() { return "I am a wombat"; }
        
    }
    
    // ---------------------------------------------------------
    // A subclass of Wombat. It's also a WombatMBean...
    //
    public static class TypedWombat extends Wombat { 
        public TypedWombat(String wombatType) {
            type=wombatType;
        }
        final String type;
        public String getDescription() { 
            return "I am a "+
                ((type==null)?"":(type+" "))+ "wombat";
        }
        public final String getKind() {
            return type;
        }
    }
    
    // ---------------------------------------------------------
    // A DomesticWombat. It has a pet name. Ours is called "Totor"...
    //
    public static interface DomesticWombatMBean extends WombatMBean {
        public String getPetName();
    }
    
    public static class DomesticWombat extends TypedWombat
        implements DomesticWombatMBean {
        public DomesticWombat() {
            super("domestic");
        }
        public String getPetName() { return "Totor"; }
    }
    
    // ---------------------------------------------------------
    // A FeralWombat. Those are very ferocious. Never mess with 
    // them...
    //
    public static interface FeralWombatMBean extends WombatMBean {
        public boolean isFerocious();
    }
    
    public static class FeralWombat  extends TypedWombat
            implements FeralWombatMBean {
        public FeralWombat() {
            super("feral");
        }
        public  boolean isFerocious() { return true; }
    }
    
    // ---------------------------------------------------------
    
    /**
     * A method that demonstrate various possibilities...
     *
     * @param args the command line arguments
     */
    public static void main(String[] args) throws Exception {

        final MBeanServer server = ManagementFactory.getPlatformMBeanServer();
        
        // We can decide that all our wombat type names end with "Wombat".
        // This will enable us to get all instance of Wombat with a simple
        // ObjectName pattern: "australia:*,type=*Wombat"
        //
        final ObjectName wombatName = 
                new ObjectName("australia:type=Wombat,name=anonymous");
        final ObjectName typedName = 
                new ObjectName("australia:type=Wombat,name=strange");
        final ObjectName domesticName = 
                new ObjectName("australia:type=DomesticWombat,name=Totor");
        final ObjectName feralName = 
                new ObjectName("australia:type=FeralWombat,name=SuperWombat");
        
        // We can also use isInstanceOf(), but there's a catch. We need to
        // use a subclass of StandardMBean loaded by a ClassLoader that can
        // also load our wombat classes. An easy (though probably not optimal
        // way to do that is to add a trailing {} to new StandardMBean(...)
        //
        // Notice the {} in 'new StandardMBean(...){}'  below...
        //
        // A better way would be to declare a:
        //
        // public static class WombatStandardMBean extends StandardMBean {
        //     public WombatStandardMBean(....) {
        //            super(...);
        //     }
        // }
        //
        // and use that. I was too lazy to do it ;-\
        //
        server.registerMBean(new StandardMBean(new Wombat(),WombatMBean.class){},wombatName);
        server.registerMBean(new StandardMBean(new TypedWombat("strange"),WombatMBean.class){},typedName);
        server.registerMBean(new StandardMBean(new DomesticWombat(),DomesticWombatMBean.class){},domesticName);
        server.registerMBean(new StandardMBean(new FeralWombat(),FeralWombatMBean.class){},feralName);
        
        // Method 1: use an ObjectName pattern. This is possible in our case
        //     because we have taken care that all our Wombat instances are
        //     named "type=XxxxWombat". 
        // However, using such a simple naming pattern may not always be 
        // feasible. In particular, if we have a deep class hierarchy.
        // For instance, we wouldn't be able to get all instance of 
        // "TypedWombat" in this way.
        //
        System.out.println("query with pattern: "+
                server.queryNames(new ObjectName("australia:*,type=*Wombat"), 
                null));
        
        // Method 2: use queryNames with an isInstanceOf query.
        // This works only on JDK 6 because that's when Query.isInstanceOf was added.
        //
        //
        // We pass a query that will call isInstanceOf() for each selected
        // MBean... This works - provided that DynamicMBeans have been properly
        // instantiated.
        //
        // This method would allow us to query for all "TypedWombat" too...
        //
        final String className = WombatMBean.class.getName();
        
        System.out.println("query with isInstanceOF: "+
                server.queryNames(new ObjectName("australia:*"), 
                Query.isInstanceOf(Query.value(className))));
        
        // Method 3: use queryNames with a wildcard, then check
        //    whether the MBean match our expectation. Here we call
        //    isInstanceof(), but we could also have tried to analyze
        //    its MBeanInfo, for instance...
        //
        // We call server.isInstanceOf() for each selected
        // MBean... This works - provided that DynamicMBeans have been properly
        // instantiated.
        // This method works also on JDK 5
        //
        System.out.println("loop...");
        for (ObjectName n:server.queryNames(new ObjectName("australia:*"), null)) {
             if (server.isInstanceOf(n,className)) 
                System.out.println(n+" is a "+className);
        }
    }
    
}