消息注册机制更加丰富了MessageHandle的流程，它把过程严格阶段化了，分成消息注册和通知消息处理两个部分，让人一目了然。

消息注册机制的总体思想是：一个对象中开辟一个空间用于存放Message，当调用regist方法时将Message存放进去，当其调用notify方法时将所有Message取出并发送到MessageQueue中等待处理。

下面是模拟程序，提供Registrant，RegistrantList，AsyncResult，MiddleUser类

package com.zte.liu.registermessage;

public class AsyncResult {

MessageParmeters parmList;
Object result;
Throwable exception;

public Throwable getException() {
return exception;
}

public void setException(Throwable exception) {
this.exception = exception;
}

AsyncResult(Object result, Throwable exception){
parmList = new MessageParmeters();
this.result = result;
this.exception = exception;
}

public MessageParmeters getMessageParms(){
return parmList;
}

public Object getResult(){
return result;
}

public void setResult(Object result){
this.result = result;
}

public AsyncResult refresh(Object parm){
parmList.refresh(parm);
return this;
}
}

package com.zte.liu.registermessage;

import com.zte.liu.messagehandler.Handler;

public class MiddleUser {

RegistrantList registrantList = new RegistrantList();

public void registForReason(Handler handler, int what, Object firstParms){
registrantList.add(handler, what, firstParms);
}

public void notifyRegistrant(Object secondParms, Throwable exception){
registrantList.notifyRegistrantList(secondParms, exception);
}

public void unRegistForReason(int what){
registrantList.remove(what);
}
}

package com.zte.liu.registermessage;

import com.zte.liu.messagehandler.Handler;
import com.zte.liu.messagehandler.Message;

public class Registrant {

private Message msg = null;

Registrant(Handler handler, int what, Object firstParms){
msg = new Message(what, handler, new AsyncResult(null, null).refresh(firstParms));
}

public void notifyRegistrant(Object secondParms, Throwable exception){
if(msg == null){
return;
}
AsyncResult asyncResult = (AsyncResult)msg.getObj();
asyncResult.refresh(secondParms).setException(exception);
msg.sendToTarget();
}

public Message getMessage(){
return msg;
}
}

package com.zte.liu.registermessage;

import java.util.ArrayList;

import com.zte.liu.messagehandler.Handler;

public class RegistrantList {

private ArrayList registrantList = new ArrayList();

public synchronized void add(Handler handler, int what, Object firstParms){
Registrant registrant = new Registrant(handler, what, firstParms);
registrantList.add(registrant);
}

public synchronized void remove(int what){
for(int i=0; i if(((Registrant)registrantList.get(i)).getMessage().getId() == what){
registrantList.remove(i);
}
}
}

public synchronized void notifyRegistrantList(Object secondParms, Throwable exception){
for(int i=0; i Registrant registrant = (Registrant)registrantList.get(i);
registrant.notifyRegistrant(secondParms, exception);
}
}

}