jmx-通訊

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

Mbean之間的通訊是必不可少的，Notification就起到了在Mbean之間溝通橋樑的做用。JMX notification 由四部分組成：

    * Notification 這個至關於一個信息包，封裝了須要傳遞的信息
    * Notification broadcaster　這至關於一個廣播器，把消息廣播出去
    * Notification listerner　這是一個監聽器，用於監聽廣播出來的Notification消息
    * Notification filter　這是一個過濾器，過濾掉不須要的Notification消息

　 Notification broadcaster不須要咱們實現，JMX的內部已經有了。Notification filter通常也不多用。下面的例子主要用到了Notification、Notification listerner。

public interface JackMBean {

    void hi();

}

/**
 * 必需繼承NotificationBroadcasterSupport
 * 此類只有一個hi方法，方法只有兩句：建立一個Notification消息包，而後將包發出去
 * 若是你還要在消息包上附加其餘數據，Notification還有一個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(//建立一個信息包
                "jack.hi",//給這個Notification起個名稱
                this, //由誰發出的Notification
                ++seq,//一系列通知中的序列號,能夠設任意數值
                System.currentTimeMillis(),//發出時間
                "Jack");//發出的消息文本
        //發出去
        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的事件模型是同樣的，另外若是你買了《Eclipse從入門到精通》，你會發現第22.4節也使用了和Notification和Java的事件模型相同的設計方式。Notification在咱們的實際項目中也用到了，象咱們如今的給移動作的項目中（基於JMX實現)，分散在各地方的工做站的日誌，就是經過Notification方式，把每條產生的日誌封裝在 Notification中實時發回主控服務器的。有機會我會發這一系統的關於日誌的設計方案寫一下，它實現了對各地工做站的集中的、實時的監控，很是實用。

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必須實現NotificationEmitter接口或
 * 繼承NotificationBroadcasterSupport類。
 * 要發送一個通知必須構造Notification類的實例
 * 或者子類(如NotificationChangedAttribute),通知實例產生後，
 * 由NotificationBroadcasterSupport的sendNotification方法發送通知。
 */
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方法的做用，暫時只知道會讓「」通知「」多一個子節點：