jdk动态代理举例

JDK动态代理是基于接口的代理，下面举例说明

• 代理类：proxy，代理动作必须要基于一个proxy实例来执行
• 代理执行类：实现InvocationHandler，案例中是TestInvocationHandler
• 被代理类：基于接口的用户自己的方法，案例中是SayImpl

首先说明下InvocationHandler的invoke

public interface InvocationHandler {

　　public Object invoke(Object proxy, Method method, Object[] args)
        　　throws Throwable;
}

proxy：方法基于哪个proxy实例来执行

method：执行proxy实例的哪个方法（proxy代理谁就执行谁的方法）

args：methed的入参

代码示例：

public interface Say {
    void sayHello(String words);
}

public class SayImpl implements Say {
    @Override
    public void sayHello(String words) {
        System.out.println("hello:" + words);
    }
}

public class TestInvocationHandler implements InvocationHandler {

    private Object target;
    public TestInvocationHandler(Object target) {
        this.target=target;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("invoke begin");
        System.out.println("method :"+ method.getName()+" is invoked!");
        method.invoke(target,args);
        System.out.println("invoke end");
        return null;
    }
}

    public static void main(String[] args) {

        TestInvocationHandler testInvocationHandler = new TestInvocationHandler(new SayImpl());
        Say say = (Say)Proxy.newProxyInstance(SayImpl.class.getClassLoader(), SayImpl.class.getInterfaces(), testInvocationHandler );
        say.sayHello("my dear");
    }

执行结果:

invoke begin
method :sayHello is invoked!
hello:my dear
invoke end