Java静态代理和动态代理总结

Posted 2020-08-31 LZHL

静态代理

第一种实现(基于接口)：

1》接口

public interface Hello {

    void say(String msg);
}

2》目标类，至少实现一个接口

public class HelloImpl implements Hello {
    public void say(String msg) {
        System.out.println("Hi,"+msg);
    }
}

3》代理类(与目标类实现相同接口，从而保证功能一致)

public class HelloProxy implements Hello{

    private Hello hello;

    public HelloProxy(Hello hello){
        this.hello = hello;
    }

    public void say(String msg){
        before();
        hello.say(msg);
        after();
    }
    private void before(){
        System.out.println("Before");
    }
    private void after(){
        System.out.println("After");
    }
}

3》测试

/**
 * @Author LZHL
 * @Create 2017-02-19 10:26
 * @Description
 */
public class Main {
    public static void main(String[] args) throws Exception {
        HelloImpl target = new HelloImpl();
        HelloProxy proxy = new HelloProxy(target);
        proxy.say("LZHL");
    }
}

第二种实现(基于目标类)：

1>目标类

public class HelloTarget {
    public void sayHello(String name){
        System.out.println("Hi,"+name);
    }
}

2>代理类(通过继承目标类，保证功能一致)

public class HelloProxy extends HelloTarget{
　　private HelloTarget target;
　　public HelloProxy(HelloTarget target){
　　　　this.target = target;
　　} 
　　@Override
    public void sayHello(String name) {
        this.before();
        target.sayHello(name);
        this.after();
    }
    private void before(){
        System.out.println("Before");
    }
    private void after(){
        System.out.println("After");
    }
}

3>测试

public class Main {
    public static void main(String[] args) throws Exception {
       HelloTarget target = new HelloTarget(); 
　　　　HelloProxy proxy= new HelloProxy(target);
       proxy.sayHello("LZHL");
    }
}

 

动态代理

动态代理的代理类是在程序运行期间动态生成的，也有两种实现，一种是JDK动态代理，一种是CGLib动态代理

1》JDK动态代理(基于接口实现，与目标类实现相同接口，从而保证功能一致)

/**
 * @Author LZHL
 * @Create 2017-02-19 12:46
 * @Description
 */
public class Main {
    public static void main(String[] args){

        final HelloImpl target = new HelloImpl();

        Object proxyInstance = Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), new InvocationHandler() {
            /*
             * proxy: 代理对象
             * method: 目标对象的方法对象
             * args: 目标对象方法的参数
             * return: 目标对象方法的返回值
             */
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                System.out.println("before");
                Object retValue = method.invoke(target, args);
                System.out.println("after");
                return retValue;
            }
        });
        Hello proxy = (Hello) proxyInstance;
        proxy.say("LYX");

        //可以把InvocationHandler提取出来，单独写一个类，为了方便大家看，这里我用内部类的形式

        class JDKProxy implements InvocationHandler {
            private Object target;
            public JDKProxy(Object target){
                this.target = target;
            }
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                before();
                Object result = method.invoke(target, args);
                after();
                return result;
            }
            private void before(){
                System.out.println("Before");
            }
            private void after(){
                System.out.println("After");
            }
        }
        InvocationHandler ih = new JDKProxy(target);
        Object proxyInstance2 = Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), ih);
        Hello proxy2 = (Hello) proxyInstance2;
        proxy2.say("LZHL");
    }
}

2》CGLib动态代理(基于目标类，通过继承目标类，从而保证功能一致)，需要导入cglib-3.2.4.jar包

pom.xml

<dependencies>
    <!-- https://mvnrepository.com/artifact/cglib/cglib -->
    <dependency>
        <groupId>cglib</groupId>
        <artifactId>cglib</artifactId>
        <version>3.2.4</version>
    </dependency>

</dependencies>

1)目标类

public class Hi {
    public void sayHi(String msg){
        System.out.println("Hi,"+msg);
    }
}

2)测试

/**
 * @Author LZHL
 * @Create 2017-02-19 13:19
 * @Description
 */
public class Main {
    public static void main(String[] args) {
        Enhancer enhancer = new Enhancer();
        //设置父类
        enhancer.setSuperclass(Hi.class);
        //设置回调函数
        enhancer.setCallback(new MethodInterceptor() {
            public Object intercept(Object target, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
                System.out.println("before");
                Object retValue = methodProxy.invokeSuper(target, args);
                System.out.println("after");
                return retValue;
            }
        });
        Object proxy = enhancer.create();
        Hi hi = (Hi) proxy;
        hi.sayHi("LXY");

        //可以把MethodInterceptor提取出来，单独写一个类，为了方便大家看，这里我用内部类的形式
        class CGLibProxy implements MethodInterceptor {

            public <T> T getProxy(Class<T> clazz){
                return (T) Enhancer.create(clazz, this);
            }
            public Object intercept(Object target, Method method, Object[] args, MethodProxy proxy) throws Throwable {
                before();
                Object result = proxy.invokeSuper(target, args);
                after();
                return result;
            }
            private void before(){
                System.out.println("Before");
            }
            private void after(){
                System.out.println("After");
            }
        }

        CGLibProxy cgLibProxy = new CGLibProxy();
        Hi hi2 = cgLibProxy.getProxy(Hi.class);
        hi2.sayHi("LZHL");
    }
}