java 动态代理实现原理

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1，UserService

public interface UserService {
public void save();
public void delete();

}

2，UserServiceImpl

public class UserServeceImpl implements UserService {

public void save() {
System.out.println("save user");
}

public void delete() {
System.out.println("delete user");

}

}

3,LogInterceptor

/**
*
* @author dwj
* 2015-7-26 下午06:43:34
*/
public class LogInterceptor implements InvocationHandler{
private Object target;//被代理对象
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-mm-dd HH:MM:ss SSS");
public void addLog(){
System.out.println("执行时间："+sdf.format(new Date()));
}
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
addLog();
method.invoke(target, args);//target 被代理的对象来调用， args是参数
return null;
}
public Object getTarget() {
return target;
}
public void setTarget(Object target) {
this.target = target;
}

}

4,ProxcyTest

public class ProxcyTest {
public static void main(String[] args){
//给哪个对象创建代理
UserService userService=new UserServeceImpl();
LogInterceptor log=new LogInterceptor();
log.setTarget(userService);
UserService userServiceProxy=(UserService) Proxy.newProxyInstance(userService.getClass().getClassLoader(), new Class[]{UserService.class}, log);
userServiceProxy.save();
userServiceProxy.delete();
}
}

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