java注解简化Swing的事件监听的实例

         在Swing的开发中常常要给Swing的组件添加相关的事件监听，编译之后生成一堆class的内部类的文件。

采用注解可以简化，组件添加事件代码的杂乱。

注解类：

package com.easyway.commons.ispace.dev.advances.dbmeta;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
 * 注解类
 * @author longgangbai
 * @date 2010-5-15
 * @version 1.0
 * @since JDK6.0
 */
@Target(ElementType.METHOD) //仅仅使用于方法
@Retention(RetentionPolicy.RUNTIME) //注解咋运行时，编译执行
public @interface ActionListenerFor {
    //注解针对的字段
	String source();
   
}

 

 注解使用的解析类：

package com.easyway.commons.ispace.dev.advances.dbmeta;

import java.awt.event.ActionListener;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
 * 运行时执行的相关的 注解代码
 * @author longgangbai
 * @date 2010-5-15
 * @version 1.0
 * @since JDK6.0
 */
public class ActionListenerInstaller {
	
	/**
	 * 注解类的处理
	 * @param o
	 */
	public static void processAnnotation(Object o) {
		try {
			Class<?> cls=o.getClass();
			for(Method m : cls.getDeclaredMethods())
			{
				ActionListenerFor actionListener=m.getAnnotation(ActionListenerFor.class);
				if(actionListener!=null){
					Field f=cls.getDeclaredField(actionListener.source());
					boolean flag=f.isAccessible();
					try{
						if(!flag){
							f.setAccessible(true);
						}
						addListener(f.get(o),o,m);
					}finally{
						f.setAccessible(flag);
					}
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	
	}
	
	/**
	 * 采用代理的形式注入相关的方法
	 * @param source
	 * @param param
	 * @param m
	 * @throws SecurityException
	 * @throws NoSuchMethodException
	 * @throws IllegalArgumentException
	 * @throws IllegalAccessException
	 * @throws InvocationTargetException
	 */
	public static void addListener(Object source,final Object param,final Method m) throws SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException{
		
		InvocationHandler handler=new InvocationHandler(){
			@Override
			public Object invoke(Object proxy, Method method, Object[] args)
					throws Throwable {
				 return m.invoke(param);
			}
		};
		Object listener=Proxy.newProxyInstance(null,new Class[]{ActionListener.class}, handler);
		Method addr=source.getClass().getMethod("addActionListener", ActionListener.class);
		addr.invoke(source, listener);
	}

}

 

 

SWing页面如下：

package com.easyway.commons.ispace.dev.advances.dbmeta;

import java.awt.Button;
import java.awt.Color;

import javax.swing.JFrame;
import javax.swing.JPanel;
/**
 * 注解的学习应用实例
 * @author longgangbai
 * @date 2010-5-15
 * @version 1.0
 * @since JDK6.0
 */
@SuppressWarnings("serial")
public class SwingActionListenerJPanel  extends JFrame{
	private JPanel panel;
	private Button yellowButton;
	private Button blueButton;
	private Button redButton;
	private static final int DEFAULTWIDTH=400;
	private static final int DEFAULTHEIGHT=500;
	
    public SwingActionListenerJPanel() {
    	setTitle("注解事件");
    	setSize(DEFAULTWIDTH,DEFAULTHEIGHT);
    	panel=new JPanel();
    	add(panel);
    	
    	yellowButton=new Button("Yellow");
    	blueButton=new Button("blue");
    	redButton=new Button("red");
    	panel.add(yellowButton);
    	panel.add(blueButton);
    	panel.add(redButton);
    	//注解的代码
    	ActionListenerInstaller.processAnnotation(this);
    } 
    //注解的方法
    @ActionListenerFor(source="redButton")
    public void redBackground(){
    	panel.setBackground(Color.RED);
    }
    @ActionListenerFor(source="blueButton")
    public void blueBackground(){
    	panel.setBackground(Color.BLUE);
    }
    @ActionListenerFor(source="yellowButton")
    public void yelllowBackground(){
    	panel.setBackground(Color.YELLOW);
    }
}