Spring AOP功能

    Spring核心思想之一是AOP(Aspect Oriented Programming)，即面向切面编程的技术。 AOP让开发人员专注核心业务，而通用逻辑则由专人使用 AOP 技术进行横向切入处理，使得任务分离，提高开发和调试的效率，应用于权限管理、日志管理等。

   假设项目已完成Spring、SpringMVC配置，添加AOP应用

1.applicationContext.xml开启支持AspectJ注解　

<?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:context="http://www.springframework.org/schema/context"
	xmlns:p="http://www.springframework.org/schema/p"
	xmlns:aop="http://www.springframework.org/schema/aop"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:task="http://www.springframework.org/schema/task"
	xsi:schemaLocation="http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
		http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-4.1.xsd
		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
	<!-- 自动扫描与装配bean -->
	<context:component-scan base-package="com.product"></context:component-scan> 
    <!-- 启动对@AspectJ注解的支持 -->
    <aop:aspectj-autoproxy/>
    <aop:aspectj-autoproxy proxy-target-class="true" /> 
</beans>

2.编写日志切面实现

   2.1 定义日志注解类

@Inherited
@Target({ElementType.TYPE, ElementType.METHOD})    
@Retention(RetentionPolicy.RUNTIME)
public @interface AppLog {
    String value() default "";
}

　2.2 日志功能

package com.product.aop;

import java.util.Arrays;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;

/**
 * 日志demo
 *  
 *
 */
@Component
@Aspect
public class LogAspect {

	private static final Log logger = LogFactory.getLog(LogAspect.class);

	//抽取公共的切入点表达式
	@Pointcut("@annotation(com.product.aop.AppLog)")
	public void pointCut() {
	};

	//在目标方法之前切入
	@Before("pointCut()")
	public void logStart(JoinPoint joinPoint) {
		Object[] args = joinPoint.getArgs();
		System.out.println("" + joinPoint.getSignature().getName() + "运行以前:参数列表是：{" + Arrays.asList(args) + "}");
	}

	@After("com.product.aop.LogAspect.pointCut()")
	public void logEnd(JoinPoint joinPoint) {
		System.out.println("" + joinPoint.getSignature().getName() + "运行结束。");
	}

	// JoinPoint在参数表的第一位
	@AfterReturning(value = "pointCut()", returning = "result")
	public void logReturn(JoinPoint joinPoint, Object result) {
		System.out.println("" + joinPoint.getSignature().getName() + "返回运行结果：{" + result + "}");
	}

	@AfterThrowing(value = "pointCut()", throwing = "exception")
	public void logException(JoinPoint joinPoint, Exception exception) {
		System.out.println("" + joinPoint.getSignature().getName() + "异常,信息：{" + exception + "}");
	}

}

3.业务功能引入切面

import org.springframework.stereotype.Service;

import com.product.aop.AppLog;

@Service("userService")
public class UserService {

	/**
	 * 标记日志注解 
	 */
	@AppLog
	public boolean exists(String userid,String name){
		System.out.println("getUser");
		return true;
	}
}

　　

4.测试

   浏览器请求http://127.0.0.1:8080/aop/user/submit.do?userid=001&name=lilei

   控制台输出结果：

   exists运行以前:参数列表是：{[001, lilei]}
      getUser
   exists运行结束。
   exists返回运行结果：{true}