Java的动态代理

// 定义接口
public interface HelloInterface {
    void sayHello();
}

// 实现接口
public class Hello implements HelloInterface {
    public void sayHello() {
        System.out.println("Hello");
    }
}

// 构建一个handler类来实现InvocationHandler接口
public class ProxyHandler implements InvocationHandler{
    private Object object;
    public ProxyHandler(Object object){
        this.object = object;
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("Before invoke "  + method.getName());
        method.invoke(object, args);
        System.out.println("After invoke " + method.getName());
        return null;
    }
}

public class demo {
    public static void main(String[] args) {
        HelloInterface hello = new Hello();

        HelloInterface proxyHello = (HelloInterface) Proxy.newProxyInstance(
            hello.getClass().getClassLoader(),
            hello.getClass().getInterfaces(),
            new ProxyHandler(hello)
        );

        proxyHello.sayHello();
    }
}

// 匿名内部类实现
public class demo {
    public static void main(String[] args) {

        final Hello hello = new Hello();

        HelloInterface proxyInstance = (HelloInterface) Proxy.newProxyInstance(
            hello.getClass().getClassLoader(),
            hello.getClass().getInterfaces(),
            new InvocationHandler() {
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                System.out.println("Before invoke " + method.getName());
                method.invoke(hello, args);
                System.out.println("After invoke " + method.getName());
                return null;
            }
        });
        proxyInstance.sayHello();
    }
}