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(){@Overridepublic 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);}}?
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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); }}?