八：动态代理的几种实现方式及优缺点

绝地灬酷狼 2022-02-04 13:47 278阅读 0赞

1.  动态代理
    
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTcyNjk3_size_16_color_FFFFFF_t_70]  
    ![学的有点蒙，。。。。。后续再写吧。。。。。。][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTcyNjk3_size_16_color_FFFFFF_t_70 1]

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

1.  有个接口 UserService

package com.enjoylearning.dynamic.proxy.jdk;
    
    import com.enjoylearning.dynamic.proxy.User;
    
    public interface UserService {
    	
    	void addUser(User user);
    
    }

1.  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][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTcyNjk3_size_16_color_FFFFFF_t_70 2]  
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;
    	}
    
    }

1.  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);
    	}
    
    }

![在这里插入图片描述][20190510173314831.png]

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[20190510173314831.png]: /images/20220204/1eda7899e8274b3b8ad37e5c663a2d87.png