动态代理

Posted 2020-12-11 limoumou

tags:

篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了动态代理相关的知识，希望对你有一定的参考价值。

动态代理:是使用反射和字节码的技术,在运行期创建指定接口或类的子类(动态代理)以及其实例对象的技术,

通过这个技术可以无侵入性的为代码进行增强;

Java的动态代理技术实现主要有两种方式：

1.JDK原生动态代理

2.CGLIB动态代理

JDK原生动态代理：

Proxy : Proxy是所有动态代理的父类,它提供了一个静态方法来创建动态代理的class对象和实例;

InvocationHandler :每个动态代理实例都有一个关联的InvocationHandler。在代理实例上调用方法
时,方法调用将被转发到InvocationHandler的invoke方法;

 1 public class User {
 2     private String name;
 3     private int age;
 4     private String address;
 5 
 6     public User(String name, int age, String address) {
 7         this.name = name;
 8         this.age = age;
 9         this.address = address;
10     }
11 
12     public String getName() {
13         return name;
14     }
15 
16     public void setName(String name) {
17         this.name = name;
18     }
19 
20     public int getAge() {
21         return age;
22     }
23 
24     public void setAge(int age) {
25         this.age = age;
26     }
27 
28     public String getAddress() {
29         return address;
30     }
31 
32     public void setAddress(String address) {
33         this.address = address;
34     }
35 
36     @Override
37     public String toString() {
38         return "User{" +
39                 "name=‘" + name + ‘‘‘ +
40                 ", age=" + age +
41                 ", address=‘" + address + ‘‘‘ +
42                 ‘}‘;
43     }
44 }

public interface UserService {
   void addUser(User user);
}


public class UserServiceImp implements UserService {

    @Override
    public final void addUser(User user) {
        System.out.println("用户存入数据库成功，数据为："+user.toString());
    }
}

public class UserServiceInterceptor implements InvocationHandler {

    private Object relobj;
    private static Logger logger=Logger.getLogger(UserServiceInterceptor.class.getName());

    public Object getRelobj() {
        return relobj;
    }

    public void setRelobj(Object relobj) {
        this.relobj = relobj;
    }

    public UserServiceInterceptor(Object relobj) {
        this.relobj = relobj;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        if(args!=null&&args.length>0&&args[0] instanceof User){
            User user= (User) args[0];
            if(user.getName().length()<=1){
                throw new RuntimeException("用户名的长度需要大于1");
            }
        }
        Object ret=method.invoke(relobj,args);
        logger.info("操作成功");
        return ret;
    }
}

public class Client {
    public static void main(String[] args) {
        User user=new User("lhh",10,"北京");
        UserService us=new UserServiceImp();
        UserServiceInterceptor usi=new UserServiceInterceptor(us);
        UserService proxy= (UserService) Proxy.newProxyInstance
                (us.getClass().getClassLoader(),us.getClass().getInterfaces(),usi);
        proxy.addUser(user);
        System.out.println(proxy.hashCode());
    }
}