AOP面向切面编程

首先新建一个maven项目，在项目的pom.xml中添加spring aop相关的依赖项：
如下是完整的pom.xml：
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 <modelVersion>4.0.0</modelVersion>

 <groupId>cn.outofmemory</groupId>
 <artifactId>spring-aop-aspect</artifactId>
 <version>0.0.1-SNAPSHOT</version>
 <packaging>jar</packaging>

 <name>spring-aop-aspect</name>
 <url>http://maven.apache.org</url>
 <properties>
  <spring.version>3.1.1.RELEASE</spring.version>
 </properties>
 <dependencies>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-core</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-context</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-aop</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.aspectj</groupId>
   <artifactId>aspectjrt</artifactId>
   <version>1.6.12</version>
  </dependency>
  <dependency>
   <groupId>org.aspectj</groupId>
   <artifactId>aspectjweaver</artifactId>
   <version>1.6.12</version>
  </dependency>
  <dependency>
   <groupId>cglib</groupId>
   <artifactId>cglib</artifactId>
   <version>2.2</version>
  </dependency>
 </dependencies>
</project>
在maven中我们引入了spring aop相关的依赖，aspectj相关的包有两个

下面我们看Aspect类：
package arch.pub.aop;

import org.apache.log4j.Logger;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;

import arch.pub.util.UtilOut;

@Component
@Aspect
public class SimpleAspect {
 private static final Logger logger = Logger.getLogger(SimpleAspect.class.getName());
 
 @Pointcut("execution(* arch.demo.controller.*Ctrl*.*(..))")
 public void pointCut() {
 }

 @After("pointCut()")
 public void after(JoinPoint joinPoint) {
  logger.error("after aspect executed");
 }

 @Before("pointCut()")
 public void before(JoinPoint joinPoint) {
  //如果需要这里可以取出参数进行处理
  //Object[] args = joinPoint.getArgs();
  logger.error("before aspect executing");
 }

 @AfterReturning(pointcut = "pointCut()", returning = "returnVal")
 public void afterReturning(JoinPoint joinPoint, Object returnVal) {
  
  logger.error("afterReturning executed, return result is "
    + returnVal);
 }

 @Around("pointCut()")
 public Object around(ProceedingJoinPoint pjp) throws Throwable {
  logger.error("around start..");
  Object object = null;
  try {
   object = pjp.proceed();
  } catch (Throwable ex) {
   logger.error("ex:------------------------------------");
   logger.error(ex.toString(), ex);
   logger.error("ex:====================================");
   object = new String("ex"); //可修改返回结果
  }
  logger.error("around end");
  return object;
 }

 @AfterThrowing(pointcut = "pointCut()", throwing = "error")
 public void afterThrowing(JoinPoint jp, Throwable error) {
  logger.error("error:------------------------------------");
  logger.error(error.toString(), error);
  logger.error("error:====================================");
 }
}
SimpleAspect类中的第一个方法是pointCut()方法，此方法无任何执行内容，只有一个@Pointcut的注解，其他方法都会引用这个注解中指定的pointcut表达式。

其他几个方法是各种Advice类型的方法实现，在这些方法中都可以通过JoinPoint实例来获得方法执行的上下文信息，参数信息。需要注意AfterReturning和AfterThrowing，After三种不同Advice的执行顺序。

有了spring框架和aspectj以及cglib的支持，我们只需要实现上面两个类就可以使用spring aop的功能了，下面我们看下如何在spring的配置文件中配置spring aop。

<?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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
                           http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
                           http://www.springframework.org/schema/aop
                           http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
                           http://www.springframework.org/schema/context
                           http://www.springframework.org/schema/context/spring-context-3.1.xsd">
    <aop:aspectj-autoproxy />
    <context:component-scan base-package="cn.outofmemory" />
</beans>

 

package cn.outofmemory.spring_aop_aspect;

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

/**
 * Hello world!
 *
 */
public class App
{
    public static void main( String[] args )
    {
     ApplicationContext appContext = new ClassPathXmlApplicationContext("/appContext.xml");
     PersonService personService = appContext.getBean(PersonService.class);
     String personName = "Jim";
     personService.addPerson(personName);
     personService.deletePerson(personName);
     personService.editPerson(personName);
     ((ClassPathXmlApplicationContext)appContext).close();
    }
}