设计模式_代理模式 - 黑马程序员技术交流社区

[Java] 纯文本查看 复制代码

public interface Subject {



    void request();

}





// 请求的真实目标对象

public class RealSubject implements Subject {

    @Override

    public void request() {

        System.out.println("real subject execute request");

    }

}





// 代理对象

public class Proxy implements Subject {



    private RealSubject realSubject;



    public Proxy(RealSubject realSubject) {

        this.realSubject = realSubject;

    }



    @Override

    public void request() {

        System.out.println("before");

        try {

            realSubject.request();

        } catch (Exception e) {

            System.out.println("ex:" + e);

            throw e;

        } finally {

            System.out.println("after");

        }





    }

}

[Java] 纯文本查看 复制代码

public class JdkProxySubject implements InvocationHandler {



    private RealSubject realSubject;



    public JdkProxySubject(RealSubject realSubject) {

        this.realSubject = realSubject;

    }



    @Override

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

        System.out.println("before");

        Object result = null;

        try {

            result = method.invoke(realSubject, args);

        } catch (Exception e) {

            System.out.println("ex" + e);

            throw e;

        } finally {

            System.out.println("after");

        }





        return result;

    }

}

[Java] 纯文本查看 复制代码

public class Client {



    public static void main(String[] args) throws Exception {

        Subject subject = (Subject) Proxy.newProxyInstance(Client.class

                .getClassLoader(), new Class[]{Subject.class}, new JdkProxySubject(new RealSubject()));



        subject.request();



    }

}

上面讲了动态代理是解决代码重复的问题。我们来验证下
首先，在Subject 接口中增加一个hello方法

[Java] 纯文本查看 复制代码

public interface Subject {



    void request();



    void hello();

}





public class RealSubject implements Subject {

    @Override

    public void request() {

        System.out.println("real subject execute request");

    }



    @Override

    public void hello() {

        System.out.println("real subject execute hello");

    }

}

静态代理类如果想要代理hello 这个方法。就要在代理类中实现这个方法

[Java] 纯文本查看 复制代码

public class Proxy implements Subject {



    private RealSubject realSubject;



    public Proxy(RealSubject realSubject) {

        this.realSubject = realSubject;

    }





    @Override

    public void hello() {

        ...

    }

}

我们看动态代理类，无需改变，直接运行测试类

[Java] 纯文本查看 复制代码

public class Client {



    public static void main(String[] args) throws Exception {

        Subject subject = (Subject) Proxy.newProxyInstance(Client.class

                .getClassLoader(), new Class[]{Subject.class}, new JdkProxySubject(new RealSubject()));



        subject.hello();



    }

}

运行结果

[Java] 纯文本查看 复制代码

before

real subject execute hello

after

代理类

[Java] 纯文本查看 复制代码

public class DemoMethodInterceptor implements MethodInterceptor {

    @Override

    public Object intercept(Object object, Method method, Object[] args, MethodProxy proxy) throws Throwable {

        System.out.println("before in cglib");

        Object result = null;

        try {

            result = proxy.invokeSuper(object,args);

        }catch (Exception e){

            System.out.println("get ex :" + e.getMessage());

            throw e;

        }finally {

            System.out.println("after in cglib");

        }

        return result;

    }

}

调用

[Java] 纯文本查看 复制代码

public class Client {



    public static void main(String[] args) {

        Enhancer enhancer = new Enhancer();

        enhancer.setSuperclass(RealSubject.class);

        enhancer.setCallback(new DemoMethodInterceptor());

        Subject subject = (Subject) enhancer.create();

        subject.request();

    }

}

运行结果

[Java] 纯文本查看 复制代码

before in cglib

real subject execute request

after in cglib