Java動態代理核心思想

• 基於cglib的動態代理，在spring的core包中添加了cglib支持，cglib是基於代理類是一個普通類，沒有接口的時候使用繼承父類（目標類）的方式來實現動態代理

public class MyBeanFartory {
	
	public static UserService createUserService(){
		
		final UserService userService = new UserService();
		final MyAspect myAspect = new MyAspect();
		
		//cglib生成代理對象的核心類
		Enhancer enhancer = new Enhancer();
		//確定父類
		enhancer.setSuperclass(UserService.class);
		//設置回調函數
		enhancer.setCallback(new MethodInterceptor(){

			@Override
			public Object intercept(Object proxy, Method method, Object[] arg2, MethodProxy arg3) throws Throwable {
				// TODO 自動生成的方法存根
				
				//前
				myAspect.before();
				//執行目標方法
				Object obj = method.invoke(userService, arg2);
				//後
				myAspect.after();
				
				return obj;
			}});
		
		//創建代理類
		UserService proxyUserService = (UserService) enhancer.create();
		
		return proxyUserService;
	}
}

•  基於jdk的動態代理，該方式需要目標類是實現接口的類

public class MyBeanFartory {
	
	public static UserService createUserService(){
		
		final UserService userService = new UserServiceImpl();
		final MyAspect myAspect = new MyAspect();
		UserService proxyService = (UserService)Proxy.newProxyInstance(MyBeanFartory.class.getClassLoader(), 
				userService.getClass().getInterfaces(), 
				new InvocationHandler(){

					@Override
					public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
						//前
						myAspect.before();
						
						Object obj = method.invoke(userService, args);
						
						//後
						myAspect.after();
						return obj;
					}});
		return proxyService;
	}
}

• 動態代理的中心思想如下：