一个简单的AOP实例

1. 创建接口类：UserService.java

package com.liaoli.service;
public interface UserService {
	public void add();
	public void delete();
	public void update();
	public void select();
}

2. 创建接口类的实现：UserServiceImpl.java

package com.liaoli.service;

public class UserServiceImpl implements UserService {
	public void add(){
		System.out.println("增加了一个用户");
	};
	public void delete(){
		System.out.println("删除了一个用户");
	};
	public void update(){
		System.out.println("修改了一个用户");
	};
	public void select(){
		System.out.println("查询了一个用户");
	};
}

3. 对接口的每个方法，不改变代码的情况下，都增加一个日志功能：
   前置日志：Log.java

package com.liaoli.log;

import java.lang.reflect.Method;
import org.springframework.aop.MethodBeforeAdvice;

public class Log implements MethodBeforeAdvice {
	public void before(Method method, Object[] args, Object target) throws Throwable {
		System.out.println(target.getClass().getName()+"被执行了");
	}
}

后置日志：AfterLog.java

package com.liaoli.log;

import java.lang.reflect.Method;
import org.springframework.aop.AfterReturningAdvice;

public class AfterLog implements AfterReturningAdvice {
	public void afterReturning(Object returnValue, Method method, Object[] args, Object target) throws Throwable {
		System.out.println("执行了:" + method.getName() + "返回结果为:" + returnValue);
	}
}

4. 配置AOP的XML配置文件：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" 
         xsi:schemaLocation="http://www.springframework.org/schema/beans 
         http://www.springframework.org/schema/beans/spring-beans.xsd
         http://www.springframework.org/schema/aop
         https://www.springframework.org/schema/aop/spring-aop.xsd">
         
         
    <!-- 注册 bean-->
    <bean id="userService" class="com.liaoli.service.UserServiceImpl"/>
	<bean id="log" class="com.liaoli.log.Log"/>
	<bean id="afterLog" class="com.liaoli.log.AfterLog"/>
	
	<!-- 配置AOP 导入AOP的约束-->
	<aop:config>
	  <!--切入点：expression表达式 execution（要执行的位置） -->
	  <aop:pointcut id="pointcut" expression="execution(* com.liaoli.service.UserServiceImpl.*(..))"/>
	  <aop:advisor advice-ref="log" pointcut-ref="pointcut" />
	  <aop:advisor advice-ref="afterLog" pointcut-ref="pointcut" />
	</aop:config>
</beans>

5. 测试类

package com.liaoli.service;

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

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

6. 运行结果
   新增
   
   删除
   

测试发现，接口的所有方法，都增加了日志功能。