Monitor.java

/*
 * Copyright (c) 2012-2014, Parallel Universe Software Co. All rights reserved.
 * 
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *  
 *   or (per the licensee's choosing)
 *  
 * under the terms of the GNU Lesser General Public License version 3.0
 * as published by the Free Software Foundation.
 */
package co.paralleluniverse.common.monitoring;

import java.lang.management.ManagementFactory;
import java.lang.ref.WeakReference;
import javax.management.InstanceAlreadyExistsException;
import javax.management.MBeanRegistrationException;
import javax.management.MBeanServer;
import javax.management.MalformedObjectNameException;
import javax.management.NotCompliantMBeanException;
import javax.management.ObjectName;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;

/**
 *
 * @author pron
 */
public abstract class Monitor<T>implements InitializingBean, DisposableBean {
    private static final Logger LOG = LoggerFactory.getLogger(Monitor.class);
    private final String name;
    private boolean registered;
    private final WeakReference<T> monitored;

    public Monitor(String name, T monitored) {
        this.name = name;
        this.monitored = new WeakReference<T>(monitored);
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        registerMBean();
    }

    @Override
    public void destroy() throws Exception {
        unregisterMBean();
    }
    
    protected T getMonitored() {
        T m  = monitored.get();
        if(m == null)
            unregisterMBean();
        return m;
    }

    protected boolean isMonitoredObjectAlive() {
        return monitored == null || monitored.get() != null;
    }

    public void registerMBean() {
        try {
            LOG.info("Registering MBean {}", name);
            MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
            ObjectName mxbeanName = new ObjectName(name);
            mbs.registerMBean(this, mxbeanName);

            this.registered = true;
        } catch (InstanceAlreadyExistsException ex) {
            throw new RuntimeException(ex);
        } catch (MBeanRegistrationException ex) {
            throw new RuntimeException(ex);
        } catch (NotCompliantMBeanException ex) {
            throw new AssertionError(ex);
        } catch (MalformedObjectNameException ex) {
            throw new AssertionError(ex);
        }
    }

    public void unregisterMBean() {
        try {
            if (registered) {
                LOG.info("Unregistering MBean {}", name);
                ManagementFactory.getPlatformMBeanServer().unregisterMBean(new ObjectName(name));
            }
            this.registered = false;
        } catch (Exception e) {
            LOG.warn("Exception:", e);
        }
    }

}