Spring的AOP配置以及常见错误（内附代码）

来源：互联网发布：易游网络验证 c# 编辑：程序博客网时间：2024/05/29 17:48

首先我们可以新建一个包，目录结构如下：

User类：

package com.hqj.aop;
public class User {
   @Override
   public String toString() {
       return "User [username=" + username + ", password=" + password + "]";
   }

   private String username;
   private String password;

   public String getUsername() {
       return username;
   }

   public void setUsername(String username) {
       this.username = username;
   }

   public String getPassword() {
       return password;
   }

   public void setPassword(String password) {
       this.password = password;
   }
}

User类接口：

package com.hqj.aop;
public interface UserDao {
public void save(User user);
}

User类接口类实现：

package com.hqj.aop;
public class UserDaoImpl implements UserDao {
   public void save(User user) {
       System.out.println("User is saved successfully");
   }
}

LogInterceptor类：

public class LogInterceptor {
   public void before() {
       System.out.println("method state");
   }

   public void after() {
       System.out.println("method after");
   }

   public void AfterReturning() {
       System.out.println("method AfterReturning");
   }

   public void AfterThrowing() {
       System.out.println("method AfterThrowing");
   }
}

AOP XML文件：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
   xmlns:context="http://www.springframework.org/schema/context"
   xmlns:aop="http://www.springframework.org/schema/aop"
   xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
   http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop-4.1.xsd
   ">
   <bean id="user" class="com.hqj.aop.User">
       <property name="username" value="Tim"></property>
       <property name="password" value="123"></property>
   </bean>
   
   <bean id="UserDaoImpl" class="com.hqj.aop.UserDaoImpl"></bean>
   
   
   <bean id="logInterceptor" class="com.hqj.aop.LogInterceptor"></bean>
   
   <aop:config proxy-target-class="true">
       
       <aop:pointcut expression="execution(* com.hqj.aop.UserDao.save(..))"
           id="servicePointcut" />
       
       <aop:aspect id="logAspect" ref="logInterceptor">
           
           <aop:before method="before" pointcut-ref="servicePointcut" />
           <aop:after method="after" pointcut-ref="servicePointcut" />
       </aop:aspect>
   </aop:config>
</beans>

测试MAIN函数：

package com.hqj.aop;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {

   public static void main(String[] args) {
       // TODO Auto-generated method stub
       ApplicationContext ctx = new ClassPathXmlApplicationContext("aop.xml");
       UserDaoImpl UDI = (UserDaoImpl) ctx.getBean("UserDaoImpl");
       User user = (User) ctx.getBean("user");
       UDI.save(user);
   }
}

运行结果：

常见错误：

com.sun.proxy.$Proxy2 cannot be cast to com.hqj.aop.UserDaoImpl
at com.hqj.aop.Main.main(Main.java:12)

解决办法：

<tx:annotation-driven transaction-manager="transactionManager"
proxy-target-class="true"/>
　　注意：proxy-target-class属性值决定是基于接口的还是基于类的代理被创建。如果proxy-target-class 属性值被设置为true，那么基于类的代理将起作用（这时需要cglib库）。如果proxy-target-class属值被设置为false或者这个属性被省略，那么标准的JDK 基于接口的代理将起作用。
即使你未声明 proxy-target-class="true" ，但运行类没有继承接口，spring也会自动使用CGLIB代理。高版本spring自动根据运行类选择 JDK 或 CGLIB 代理package com.hqj.aop;

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