【反射】代理

1.静态代理

package proxy;

public interface Greeting {
    void sayHello(String name);
}

package proxy;

public class GreetingImpl implements Greeting {
    @Override
    public void sayHello(String name) {
        System.out.println("Hello," + name);
    }
}

package proxy;

import java.util.logging.Level;
import java.util.logging.Logger;

public class GreetingProxy implements Greeting {

    private Logger logger = Logger.getLogger(this.getClass().getName());
    private Greeting greetingObj;

    public GreetingProxy(Greeting greetingObj) {
        this.greetingObj = greetingObj;
    }

    @Override
    public void sayHello(String name) {
        logger.log(Level.INFO, "sayHello method starts...");

        greetingObj.sayHello(name);

        logger.log(Level.INFO, "sayHello method ends...");
    }
}

2.动态代理

package proxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.logging.Level;
import java.util.logging.Logger;

public class LogHandler implements InvocationHandler {

    private Logger logger = Logger.getLogger(this.getClass().getName());
    private Object originalObj;

    public Object bind(Object obj){
        this.originalObj = obj;
        return Proxy.newProxyInstance(originalObj.getClass().getClassLoader(),
                originalObj.getClass().getInterfaces(),
                this
                );
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        Object result = null;
        logger.log(Level.INFO,"method starts..."+method);
        result = method.invoke(originalObj,args);
        logger.log(Level.INFO,"method ends..."+method);
        return result;
    }
}

3.调用

package proxy;

public class Client {
    public static void welcome(Greeting greeting,String name){
        greeting.sayHello(name);
    }

    public static void main(String[] args) {
        GreetingImpl greeting = new GreetingImpl();
        welcome(greeting,"张三");
        System.out.println("-----------------------------");
        //使用代理
        GreetingProxy greetingProxy = new GreetingProxy(greeting);
        welcome(greetingProxy,"李四");

        //动态代理
        Greeting handler = (Greeting)new LogHandler().bind(greeting);
        handler.sayHello("王五");
    }

}