spring aop

spring aop是面向切面的编程，是面向对象编程的一个拓展。面向切面是指不侵入源代码的情况下，让主业务暴露一个切点，通过切点实现添加的非主业务。这样实现了解耦，提高代码的灵活性，重用性。实现aop有四种方法

1.经典的基于代理的AOP
2.@AspectJ注解驱动的切面
3.纯POJO切面
4.注入式AspectJ切面

这里我们只介绍第二种方法

1.实现接口UserDao

package com.bjsxt.dao.impl;
import org.springframework.stereotype.Component;
import com.bjsxt.dao.UserDAO;
import com.bjsxt.model.User;
@Component("u") 
public class UserDAOImpl implements UserDAO {
    public void save(User user) {
        //Hibernate
        //JDBC
        //XML
        //NetWork
        System.out.println("user saved!");
        //throw new RuntimeException("exeption!");
    }

}

2.service层

package com.bjsxt.service;
import javax.annotation.Resource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;
import com.bjsxt.dao.UserDAO;
import com.bjsxt.model.User;
@Component("userService")
public class UserService {
    private UserDAO userDAO;  
    public void init() {
        System.out.println("init");
    }
    
    public void add(User user) {
        userDAO.save(user);
    }
    public UserDAO getUserDAO() {
        return userDAO;
    }
    
    @Resource(name="u")
    public void setUserDAO( UserDAO userDAO) {
        this.userDAO = userDAO;
    }
    public void destroy() {
        System.out.println("destroy");
    }
}

3.LogInterceptor

package com.bjsxt.aop;
import org.aspectj.lang.ProceedingJoinPoint;
//@Aspect
//@Component
public class LogInterceptor {
    //@Pointcut("execution(public * com.bjsxt.service..*.add(..))")
    public void myMethod(){};
    
    //@Before("myMethod()")
    public void before() {
        System.out.println("method before");
    }
    public void after(){
        System.out.println("method after");
    }
    
    //@Around("myMethod()")
    public void aroundMethod(ProceedingJoinPoint pjp) throws Throwable {
        System.out.println("method around start");
        pjp.proceed();
        System.out.println("method around end");
    }
    
}

4.applicationContext.xml

<?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:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
      http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-3.0.xsd
           http://www.springframework.org/schema/aop
           http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">
    <context:annotation-config />
    <context:component-scan base-package="com.bjsxt"/>
    <!-- <aop:aspectj-autoproxy></aop:aspectj-autoproxy> -->
    <bean id="logInterceptor" class="com.bjsxt.aop.LogInterceptor"></bean>
    <aop:config>
        
        <aop:aspect id="logAspect" ref="logInterceptor">
            <aop:before method="before" pointcut="execution(public * com.bjsxt.service..*.add(..))" />
            <aop:after method="after" pointcut="execution(public * com.bjsxt.service..*.add(..))"/>
        </aop:aspect>
    
    </aop:config>


</beans>

5.test

public class UserServiceTest {
    public static void main(String[] args){
        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService service = (UserService)ctx.getBean("userService");
        System.out.println(service.getClass());
        service.add(new User());
        ctx.destroy();
        
    
    }

上面是使用xml方式

如果使用annotation方式的话将3.logInterceptor的注释打开

applicationContext.xml

<context:annotation-config />
    <context:component-scan base-package="com.bjsxt"/>
     <aop:aspectj-autoproxy />

这里就实现了aop

aop主要用来

日志记录，性能统计，安全控制，事务处理，异常处理 等等