代理模式

• 意图: 为其它对象提供一种代理以控制这个对象的访问
• 应用: Spring AOP

实现

public interface Animal {
    void eat();
}

public class Dog implements Animal {

    private String name;

    public Dog(String name) {
        this.name = name;
    }

    @Override
    public void eat() {
        System.out.println(name + " is eating!");
    }
}

静态代理

public class AnimalStaticProxy implements Animal {

    private Dog dog;
    private String name;

    public AnimalStaticProxy(String name) {
        this.name = name;
        dog = new Dog(name);
    }

    @Override
    public void eat() {
        System.out.println("Dog eat before...");
        dog.eat();
        System.out.println("Dog eat after...");
    }
}

动态代理

public class AnimalDynamicProxy<T> implements InvocationHandler {

    private T target;

    public AnimalDynamicProxy(T target) {
        this.target = target;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("Dog eat before...");
        Object result = method.invoke(target, args);
        System.out.println("Dog eat after...");
        return result;
    }
}

调用

public class ProxyPatternDemo {
    public static void main(String[] args) {
        // static proxy
        System.out.println("== STATIC PROXY==");
        Animal animal1 = new AnimalStaticProxy("gigi");
        animal1.eat();

        // dynamic proxy
        System.out.println("== DYNAMIC PROXY==");
        Animal animal2 = (Animal) Proxy.newProxyInstance(Animal.class.getClassLoader(), new Class<?>[]{Animal.class}, new AnimalDynamicProxy<Dog>(new Dog("kiki")));
        animal2.eat();
    }
}

运行结果