八：动态代理的几种实现方式及优缺点-蒲公英云

八：动态代理的几种实现方式及优缺点

动态代理

JDK 代码示例：需求， user 实体类值写入到数据库时，校验name 长度不能小于1
无侵入性增强

有个接口 UserService

package com.enjoylearning.dynamic.proxy.jdk;

import com.enjoylearning.dynamic.proxy.User;

public interface UserService {
```
void addUser(User user);
```
}
被增强的类必须要继承接口

package com.enjoylearning.dynamic.proxy.jdk;

import com.enjoylearning.dynamic.proxy.User;

public class UserServiceImpl implements UserService {
```
@Override
public final void addUser(User user) {
    System.out.println("用户数据入库成功，数据为：" + user.toString());
}
```
}

3.拦截器

package com.enjoylearning.dynamic.proxy.jdk;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.util.logging.Logger;
import com.enjoylearning.dynamic.proxy.User;
public class UserServiceInterceptor implements InvocationHandler{
    private Object realObj;
    private static Logger logger = Logger.getLogger(UserServiceInterceptor.class.getName());
    public Object getRealObj() {
        return realObj;
    }
    public void setRealObj(Object realObj) {
        this.realObj = realObj;
    }
    public UserServiceInterceptor(Object realObj) {
        super();
        this.realObj = realObj;
    }
    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().trim().length()<=1){
                throw new RuntimeException("用户姓名输入长度需要大于1！");
            }
        }
        Object ret = method.invoke(realObj, args);
        logger.info("数据库操作成功！");
        return ret;
    }
}

4.测试方法

package com.enjoylearning.dynamic.proxy.jdk;
import java.lang.reflect.Proxy;
import com.enjoylearning.dynamic.proxy.User;
public class Client {
    public static void main(String[] args) {
        User user = new User();
        user.setAddress("地址");
        user.setAge(20);
        user.setName("1ison");
        UserService us = new UserServiceImpl();
        UserServiceInterceptor usi = new UserServiceInterceptor(us);
        //1.类加载器
        //2. 服务接口信息
        //3. invocationhandler 本身
        UserService proxy = (UserService) Proxy.newProxyInstance(us.getClass().getClassLoader(), us.getClass().getInterfaces(), usi);
        //通过动态代理增强业务
        proxy.addUser(user);
//        System.out.println("---------------------");
//        System.out.println(proxy.hashCode());
    }
}

CGLIB 动态代理

在这里插入图片描述
1.被增强的方法，不需要继承接口

package com.enjoylearning.dynamic.proxy.cglib;
import com.enjoylearning.dynamic.proxy.User;
public class UserServiceImpl {
    public final void addUser(User user) {
        System.out.println("用户数据入库成功，数据为："+user.toString());
    }
}

2.拦截器实现intercept 方法

package com.enjoylearning.dynamic.proxy.cglib;
import java.lang.reflect.Method;
import java.util.logging.Logger;
import com.enjoylearning.dynamic.proxy.User;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
public class UserServiceInterceptor implements MethodInterceptor {
    private static Logger logger = Logger.getLogger(UserServiceInterceptor.class.getName());
    public Object intercept(Object obj, Method method, Object[] args,MethodProxy proxy) throws Throwable {
        if(args!=null && args.length>0 && args[0] instanceof User){
            User user = (User) args[0];
            if(user.getName().trim().length() <= 1){
                throw new RuntimeException("用户姓名输入长度需要大于1！");
            }
        }
        Object ret = proxy.invokeSuper(obj, args);
        logger.info("数据库操作成功！");
        return ret;
    }
}

测试类

package com.enjoylearning.dynamic.proxy.cglib;

import com.enjoylearning.dynamic.proxy.User;

import net.sf.cglib.proxy.Enhancer;

public class Client {
```
public static void main(String[] args) {
    User user = new User();
    user.setAddress("地址");
    user.setAge(20);
    user.setName("lison");
    Enhancer enhancer = new Enhancer();
    enhancer.setSuperclass(UserServiceImpl.class);
    enhancer.setCallback(new UserServiceInterceptor());
    UserServiceImpl usi1 = (UserServiceImpl) enhancer.create();
    usi1.addUser(user);
```
// System.out.println(“——————————-“);
// System.out.println(usi.hashCode());

// UserServiceImpl us = new UserServiceImpl();
// enhancer.setCallback(new UserServiceDelegateInterceptor(us));
// UserServiceImpl usi2 = (UserServiceImpl) enhancer.create();
// usi2.addUser(user);
```
}
```
}