Spring框架AOP添加日志记录功能

需求，在调用业务方法的时候，在被调用的业务方法的前面和后面添加上日志记录功能

整体架构：

 日志处理类：

package aop;

import java.util.Arrays;

import org.apache.log4j.Logger;
import org.aspectj.lang.JoinPoint;

//日志处理类  增强处理类-日志
public class UserServiceLogger {
    private Logger logger = Logger.getLogger(UserServiceLogger.class);

    // 前置增强
    public void before(JoinPoint joinPoint) {
        logger.info("调用" + joinPoint.getTarget() + "的"
                + joinPoint.getSignature() + "方法，方法参数是："
                + Arrays.toString(joinPoint.getArgs()));
    }

    // 后置增强
    public void afterReturning(JoinPoint joinPoint,Object result) {
        logger.info("调用" + joinPoint.getTarget() + "的"
                + joinPoint.getSignature() + "方法，方法的返回值是："
                +result);
    }
}

下面是一个三层架构模式： 
1 package dao;

import entity.User;

/**
 * 增加DAO接口,定义了所需的持久化方法
 */
public interface UserDao {
    public void save(User user);
}

package dao.impl;

import dao.UserDao;
import entity.User;

/**
 * 用户DAO类，实现IDao接口，负责User类的持久化操作
 */
public class UserDaoImpl implements UserDao {

    public void save(User user) {
        // 这里并未实现完整的数据库操作，仅为说明问题
        System.out.println("保存用户信息到数据库");
    }
}

package entity;

/**
 * 用户实体类
 */
public class User implements java.io.Serializable {
    private Integer id; // 用户ID
    private String username; // 用户名
    private String password; // 密码
    private String email; // 电子邮件

    // getter & setter
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    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;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

}

package service;

import entity.User;

/**
 * 用户业务接口，定义了所需的业务方法
 */
public interface UserService {
    public void addNewUser(User user);
}

package service.impl;

import service.UserService;
import dao.UserDao;
import entity.User;

/**
 * 用户业务类，实现对User功能的业务管理
 */
public class UserServiceImpl implements UserService {

    // 声明接口类型的引用，和具体实现类解耦合
    private UserDao dao;

    // dao 属性的setter访问器，会被Spring调用，实现设值注入
    public void setDao(UserDao dao) {
        this.dao = dao;
    }

    public void addNewUser(User user) {
        // 调用用户DAO的方法保存用户信息
        dao.save(user);
    }
}

编写单元测试方法：
package test;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import service.UserService;
import service.impl.UserServiceImpl;

import entity.User;


public class AopTest {

    @Test
    public void aopTest() {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService service = (UserService) ctx.getBean("service");
        
        User user = new User();
        user.setId(1);
        user.setUsername("test");
        user.setPassword("123456");
        user.setEmail("test@xxx.com");

        service.addNewUser(user);
    }

}

applicationContext.xml核心配置文件：

<?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:aop="http://www.springframework.org/schema/aop"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
    http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop-3.2.xsd">
    <bean id="dao" class="dao.impl.UserDaoImpl"></bean>
    <bean id="service" class="service.impl.UserServiceImpl">
        <property name="dao" ref="dao"></property>
    </bean>
    <!-- 声明增强方法所在的Bean -->
    <bean id="theLogger" class="aop.UserServiceLogger"></bean>
    <!-- 配置切面 -->
    <aop:config>
        <!-- 定义切入点 -->
        <aop:pointcut id="pointcut"
            expression="execution(public void addNewUser(entity.User))" />
        <!-- 引用包含增强方法的Bean -->
        <aop:aspect ref="theLogger">
            <!-- 将before()方法定义为前置增强并引用pointcut切入点 -->
            <aop:before method="before" pointcut-ref="pointcut"></aop:before>
            <!-- 将afterReturning()方法定义为后置增强并引用pointcut切入点 -->
            <!-- 通过returning属性指定为名为result的参数注入返回值 -->
            <aop:after-returning method="afterReturning"
                pointcut-ref="pointcut" returning="result" />
        </aop:aspect>
    </aop:config>
</beans>

运行结果：

12-29 15:13:06[INFO]org.springframework.context.support.ClassPathXmlApplicationContext
 -Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@2db0f6b2: startup date [Sun Dec 29 15:13:06 CST 2019]; root of context hierarchy
12-29 15:13:06[INFO]org.springframework.beans.factory.xml.XmlBeanDefinitionReader
 -Loading XML bean definitions from class path resource [applicationContext.xml]
12-29 15:13:06[INFO]org.springframework.beans.factory.support.DefaultListableBeanFactory
 -Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@3701eaf6: defining beans [userDao,service,theLogger,org.springframework.aop.config.internalAutoProxyCreator,pointcut,org.springframework.aop.aspectj.AspectJPointcutAdvisor#0,org.springframework.aop.aspectj.AspectJPointcutAdvisor#1]; root of factory hierarchy
12-29 15:13:06[INFO]aop.UserServiceLogger
 -调用service.impl.UserServiceImpl@3c130745的void service.UserService.addNewUser(User)方法，方法参数是：[entity.User@2e4b8173]
保存用户信息到数据库
12-29 15:13:06[INFO]aop.UserServiceLogger
 -调用service.impl.UserServiceImpl@3c130745的void service.UserService.addNewUser(User)方法，方法的返回值是：null