jmx-通信

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http://www.blogjava.net/hengheng123456789/articles/66095.html

Mbean之间的通信是必不可少的，Notification就起到了在Mbean之间沟通桥梁的作用。JMX notification 由四部分组成：

    * Notification 这个相当于一个信息包，封装了需要传递的信息
    * Notification broadcaster　这相当于一个广播器，把消息广播出去
    * Notification listerner　这是一个监听器，用于监听广播出来的Notification消息
    * Notification filter　这是一个过滤器，过滤掉不需要的Notification消息

　 Notification broadcaster不需要我们实现，JMX的内部已经有了。Notification filter一般也很少用。下面的例子主要用到了Notification、Notification listerner。

public interface JackMBean {

    void hi();

}

/**
 * 必需继承NotificationBroadcasterSupport
 * 此类只有一个hi方法，方法只有两句：创建一个Notification消息包，然后将包发出去
 * 如果你还要在消息包上附加其他数据，Notification还有一个setUserData方法可供使用
 */
public class Jack extends NotificationBroadcasterSupport implements JackMBean {

    private int seq = 0;
    @Override
    public void hi() {
        Notification n = new Notification(//创建一个信息包
                "jack.hi",//给这个Notification起个名称
                this, //由谁发出的Notification
                ++seq,//一系列通知中的序列号,可以设任意数值
                System.currentTimeMillis(),//发出时间
                "Jack");//发出的消息文本
        //发出去
        sendNotification(n);
    }

}

public class HelloListener implements NotificationListener {
    public void handleNotification(Notification n, Object handback) {
        System.out.println("type=" + n.getType());
        System.out.println("source=" + n.getSource());
        System.out.println("seq=" + n.getSequenceNumber());
        System.out.println("send time=" + n.getTimeStamp());
        System.out.println("message=" + n.getMessage());

        if (handback != null) {
            if (handback instanceof HelloWorld) {
                HelloWorld hello = (HelloWorld) handback;
                hello.printHello(n.getMessage());
            }
        }
    }
}

public class HelloNotifyAgent {

    public static void main (String args[]) throws Exception{
        MBeanServer server = ManagementFactory.getPlatformMBeanServer();
        ObjectName helloName = new ObjectName("HelloAgent:name=HelloWorld");
        HelloWorld hello=new HelloWorld();
        server.registerMBean(hello, helloName);
        ObjectName adapterName = new ObjectName("HelloAgent:name=htmlAdapter");
        HtmlAdaptorServer adapter = new HtmlAdaptorServer();
        server.registerMBean(adapter, adapterName);
        Jack jack = new Jack();
        server.registerMBean(jack, new ObjectName("HelloAgent:name=jack"));
        jack.addNotificationListener(new HelloListener(), null, hello);
        adapter.start();
        System.out.println("start.....");
    }


}

Notification和Java的事件模型是一样的，另外如果你买了《Eclipse从入门到精通》，你会发现第22.4节也使用了和Notification和Java的事件模型相同的设计方式。Notification在我们的实际项目中也用到了，象我们现在的给移动做的项目中（基于JMX实现)，分散在各地方的工作站的日志，就是通过Notification方式，把每条产生的日志封装在 Notification中实时发回主控服务器的。有机会我会发这一系统的关于日志的设计方案写一下，它实现了对各地工作站的集中的、实时的监控，非常实用。

another example

public interface HelloMBean {

    void sayHello();

    int add(int x, int y);

    String getName();

    int getCacheSize();

    void setCacheSize(int size);

}

/**
 * 要生成通知，MBean必须实现NotificationEmitter接口或
 * 继承NotificationBroadcasterSupport类。
 * 要发送一个通知必须构造Notification类的实例
 * 或者子类(如NotificationChangedAttribute),通知实例产生后，
 * 由NotificationBroadcasterSupport的sendNotification方法发送通知。
 */
public class Hello extends NotificationBroadcasterSupport implements HelloMBean {
    private final String name = "Reginald";
    private int cacheSize = DEFAULT_CACHE_SIZE;
    private static final int DEFAULT_CACHE_SIZE = 200;
    private long sequenceNumber = 1;

    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) {
        int oldSize = this.cacheSize;
        this.cacheSize = size;
        System.out.println("Cache size now " + this.cacheSize);

        /**
         * To send a notification,you need to construct an instance of class
         * Notification or a Subclass(such as AttributeChangedNotification),and
         * pass the instance to NotificationBroadcastSupport.sendNotification.
         *
         */
        Notification n = new AttributeChangeNotification(this,
                sequenceNumber++, System.currentTimeMillis(),
                "CacheSize changed", "CacheSize", "int", oldSize,
                this.cacheSize);

        sendNotification(n);
    }

    @Override
    public MBeanNotificationInfo[] getNotificationInfo() {
        String[] types = new String[] { AttributeChangeNotification.ATTRIBUTE_CHANGE };
        String name = AttributeChangeNotification.class.getName();
        String description = "An attribute of this MBean has changed";
        MBeanNotificationInfo info = new MBeanNotificationInfo(types, name,
                description);
        return new MBeanNotificationInfo[] { info };
    }
}


public class MBeanRun {

    public static void main(String[] args) throws Exception{
        MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
        ObjectName name = new ObjectName("com.jmx.demo:type=Hello");
        Hello mbean = new Hello();
        mbs.registerMBean(mbean, name);
        System.out.println("Waiting forever...");
        Thread.sleep(Long.MAX_VALUE);

    }

}

getNotificationInfo方法的作用，暂时只知道会让“”通知“”多一个子节点：

转载于:https://my.oschina.net/u/1380557/blog/798549