notificationmonitor.java

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package org.sadun.jmx;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.LinkedList;
import java.util.List;

import javax.management.MBeanRegistration;
import javax.management.MBeanServer;
import javax.management.Notification;
import javax.management.NotificationListener;
import javax.management.ObjectName;

/**
 * A minimal notification monitor keeping core log
 * of JMX notifications.
 * 
 *
 * @author Cristiano Sadun
 */
public class NotificationMonitor implements MBeanRegistration, NotificationMonitorMBean,
        NotificationListener {

    private List notifications = new LinkedList();
    private int logSize = 100;
    private ObjectName mbeanName;

    public NotificationMonitor() {
        System.out.println("Notifications monitor v1.0 instance created");
    }

    public synchronized void handleNotification(Notification notification,
            Object handback) {
        System.out.println("Notification received: "+notification+" (total of "+notifications.size()+" registered so far)");
        if (notifications.size() > logSize)
            notifications.remove(notifications.size());
        notifications.add(0, notification);
    }

    public int getMaxLogSize() {
        return logSize;
    }

    public void setMaxLogSize(int logSize) {
        this.logSize = logSize;
    }

    public String listNotifications() {
        return head(-1);
    }

    public String tail(int n) {
        return list(n, false);
    }
    
    public int logSize() {
        return notifications.size();
    }
    
    public synchronized void cleanUp() {
        notifications.removeAll(notifications);
    }
    
    /*
    public void listenTo(String mbeanName) throws MBeanException {
        ArrayList a = MBeanServerFactory.findMBeanServer(null);
        MBeanServer mbs = (MBeanServer)a.get(0);
        try {
            mbs.addNotificationListener(new ObjectName(mbeanName), this, null, null );
        } catch (InstanceNotFoundException e) {
            throw new MBeanException(e);
        } catch (MalformedObjectNameException e) {
            throw new MBeanException(e);
        }
    }
    
    public void listenToDirectoryPoller() throws MBeanException {
        listenTo("user:service=DirectoryPoller");
    }*/

    private synchronized String list(int n, boolean forward) {
        int l = notifications.size();
        if (n == -1) {
            n = l;
        }

        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw);
        for (int i = 0; i < n; i++) {
            pw.println(notifications.get(forward ? i : l - i));
        }
        return sw.toString();
    }

    public String head(int n) {
        return list(n, true);
    }
    
    public void postDeregister() {
        // Do nothing
        
    }
    
    public void postRegister(Boolean arg0) {
        
    }
    
    public void preDeregister() throws Exception {
        // Do nothing
        
    }
    
    public ObjectName preRegister(MBeanServer arg0, ObjectName name) throws Exception {
        this.mbeanName=name;
        return name;
    }

}