Spring AOP简单实现

　Spring AOP - Aspect Oriented Programming面向切面编程，在不修改源码的情况下对程序行为进行拓展。AOP的做法是将通用、与业务无关的功能抽象封装为切面类，切面可配置在目标方法的执行前、后运行，真正做到即插即用。

 用AOP实现在所有方法调用前打印时间

　在pom.xml中依赖AspectJ——实现切面类MethodAspect和切面方法printExecutionTime——在applicationContext中配置切面类——定义PointCut，描述切面的作用范围——配置Adivice通知，说明切面的执行时机

<dependencies>
    <dependency>
        <groupId>org.springframeworkgroupId>
        <artifactId>spring-contextartifactId>
        <version>5.3.17version>
    dependency>
    <dependency>
        <groupId>org.aspectjgroupId>
        <artifactId>aspectjweaverartifactId>
        <version>1.9.9.1version>
    dependency>
dependencies>

package com.spring.aoc.dao;

public class EmployeeDao {
    public void insert(){
        System.out.println("新增员工数据");
    }
}

package com.spring.aoc.dao;

public class UserDao {
    public void insert(){
        System.out.println("新增用户数据");
    }
}

package com.spring.aoc.service;

import com.spring.aoc.dao.EmployeeDao;

/**
 * 员工服务
 */
public class EmployeeService {
    private EmployeeDao employeeDao;

    public void entry(){
        System.out.println("执行员工入职业务逻辑");
        employeeDao.insert();
    }

    public EmployeeDao getEmployeeDao() {
        return employeeDao;
    }

    public void setEmployeeDao(EmployeeDao employeeDao) {
        this.employeeDao = employeeDao;
    }
}

package com.spring.aoc.service;

import com.spring.aoc.dao.UserDao;

public class UserService {
    private UserDao userDao;

    public void createUser(){
        System.out.println("执行创建用户业务逻辑");
        userDao.insert();
    }

    public String generateRandomPassword(String type , Integer length){
        System.out.println("按" + type + "方式生成" + length + "位随机密码");
        return "JIUjKJ51";
    }

    public UserDao getUserDao() {
        return userDao;
    }

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
}

package com.spring.aoc.aspect;

import org.aspectj.lang.JoinPoint;

import java.text.SimpleDateFormat;
import java.util.Date;

//切面类
public class MethodAspect {
    //切面方法，用于扩展额外的功能，JoinPoint 连接点
    //通过连接点可以获取目标类/目标方法的信息
    public void printExecutionTime(JoinPoint joinPoint){
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss SSS");
        String now = sdf.format(new Date());
        String className = joinPoint.getTarget().getClass().getName();//获取目标类的名称
        String methodName = joinPoint.getSignature().getName();//获取目标方法的名称
        System.out.println("---->" + now + ":" + className + "." + methodName);
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns="http://www.springframework.org/schema/beans"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd">
    <bean id="userDao" class="com.spring.aoc.dao.UserDao"/>
    <bean id="employeeDao" class="com.spring.aoc.dao.EmployeeDao"/>
    <bean id="userService" class="com.spring.aoc.service.UserService">
        <property name="userDao" ref="userDao"/>
    bean>
    <bean id="employeeService" class="com.spring.aoc.service.EmployeeService">
        <property name="employeeDao" ref="employeeDao"/>
    bean>
    
    <bean id="methodAspect" class="com.spring.aoc.aspect.MethodAspect">bean>
    <aop:config>
        
        
        <aop:pointcut id="pointcut" expression="execution(public * com.spring..*.*(..))"/>
        
        <aop:aspect ref="methodAspect">
            
            <aop:before method="printExecutionTime" pointcut-ref="pointcut"/>
        aop:aspect>
    aop:config>
beans>

package com.spring.aoc;

import com.spring.aoc.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringApplication {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
        UserService userService = context.getBean("userService", UserService.class);
        userService.createUser();
    }
}