代理模式

1. 介绍

代理模式给某一个对象提供一个代理对象，并由代理对象控制对原对象的引用。通俗的来讲代理模式就是我们生活中常见的中介。

2. 应用场景

日志记录,在一个方法处理前后增加自己的功能

3. 代码实现

3.1 静态代理

3.1.1 代理接口

public interface Moveable {
     void go();
}

3.1.2 接口实现类

public class Bike implements Moveable {
    @Override
    public void go() {
        System.out.println(" bike 蹬蹬蹬");
    }
}

public class Car implements Moveable {
    @Override
    public void go() {
        System.out.println("car 咻咻咻......");
    }
}

3.1.3 代理类

public class LogProxy implements Moveable {
    private Moveable m;

    public LogProxy(Moveable m) {
        this.m = m;
    }

    @Override
    public void go() {
        System.out.println("开始记录日志");
        m.go();
        System.out.println("结束记录日志");

    }
}

public class TimeProxy implements Moveable {
    private Moveable m;

    public TimeProxy(Moveable m) {
        this.m = m;
    }

    @Override
    public void go() {
        System.out.println("开始发动时间");
        m.go();
        System.out.println("发动结束");

    }
}

3.1.4 调用入口

public class Main {
    public static void main(String[] args) {
        Moveable a = new TimeProxy(new LogProxy(new Car()));
        a.go();
        System.out.println("===========================================");
        Moveable b = new TimeProxy(new LogProxy(new Train()));
        b.go();
    }
}

3.2 jdk动态代理

必须继承接口

3.2.1 接口类

public interface Moveable {
     void go();
}

3.2.2 接口实现类

public class Bike implements Moveable {
    @Override
    public void go() {
        System.out.println(" bike 蹬蹬蹬");
    }
}

public class Car implements Moveable {
    @Override
    public void go() {
        System.out.println("car 咻咻咻......");
    }
}

3.2.3 代理类

public class TimeHandler implements InvocationHandler {
    private Moveable m;

    public TimeHandler(Moveable m) {
        this.m = m;
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("开始发动时间");
        Object obj = method.invoke(m, args);
        System.out.println("发送结束");
        return obj;
    }
}

3.2.4 调用入口

public class Main {
    public static void main(String[] args) {
        System.setProperty("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");

        Moveable car = new Car();
        //reflection 通过二进制字节码分析类的属性和方法
        Moveable m = (Moveable)Proxy.newProxyInstance(Moveable.class.getClassLoader(),
                new Class[]{Moveable.class}, //tank.class.getInterfaces()
                new TimeHandler(car)
        );

        m.go();
    }
}

3.3 cglib代理

pom文件

 <!-- https://mvnrepository.com/artifact/cglib/cglib -->
<dependency>
    <groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>3.3.0</version>
</dependency>

3.3.1 实现类

可以不继承接口

public class Bike implements Moveable {
    @Override
    public void go() {
        System.out.println(" bike 蹬蹬蹬");
    }
}

3.3.2 代理类

public class TimeProxy implements MethodInterceptor {
    @Override
    public Object intercept(Object o, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
        System.out.println("开始发动");
        Object result = methodProxy.invokeSuper(o, args);
        System.out.println("发送结束");
        return result;
    }
}

3.3.4 调用入口

public class TimeProxy implements MethodInterceptor {
    @Override
    public Object intercept(Object o, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
        System.out.println("开始发动");
        Object result = methodProxy.invokeSuper(o, args);
        System.out.println("发送结束");
        return result;
    }
}

来源：oschina

链接：https://my.oschina.net/u/4160362/blog/4295231