1. 概要
AspectJ 支持 5 种类型的通知注解:
@Before: 前置通知,在方法执行之前执行
@After: 后置通知,在方法执行之后执行
@AfterRunning: 返回通知,在方法返回结果之后执行
@AfterThrowing: 异常通知,在方法抛出异常之后
@Around: 环绕通知,围绕着方法执行
前置通知:@Before
@Aspect
public class AudienceAdvice {
@Before("execution(* WelcomeService.*(..))")
public void takeSeats(){..}
@Before("execution(* WelcomeService.*(..))")
public void turnOffCellphone(JoinPoint jp){..}
JoinPoint参数可访问连接点细节,入方法名和参数等.
jp.getTarget()//目标对象
jp.getThis()//当前的代理对象
jp.getArgs();//方法调用参数
jp.getSignature().getName()//方法签名
后置通知:@After
@After("execution(* *..WelcomeService.*(..))")
public void applaud(){..}
后置通知在目标方法执行完成之后执行.一个切面aspect包含很多通知.
@After
后置通知表明目标方法执行完之后,不论是否抛异常,都会织入该通知.
@AfterReturning
方法返回后通知只在目标方法返回以后执行,若抛异常不执行.
@AfterReturning(pointcut="",returning="res")
public void xxx(Joinput jp,Object res)
在后置通知中可接收到返回值.res即是用来接收返回值的对象.
环绕通知:@Around
@Around("execution(* *..WelcomeService.*(..))")
public void around(ProceedingPointCut jp){..}
注意:可以控制目标方法是否调用,以及返回完全不同的对象,要慎用.
指定优先级:
@Aspect
@Order(0)
public class xxx{...}
加上@Order注解可以指定加入切面的优先级(先后顺序,值越小,优先级越高)
引入通知:
@Aspect
public class MyAspectjIntroduction {
@DeclareParents(value="*..*Service*",
defaultImpl=ModifyDateImpl.class)
private ModifyDate md ;
}
value:指定哪些类可以应用该属性
defaultImpl:指定接口的实现类
典型Aspectj切入点表达式定义:
execution(* cn.itcast.WelcomeServiceImpl.*(..))
execution(public * *..WelcomeServiceImpl.*(..))
execution(public void *..WelcomeServiceImpl.*(..))
execution(public void *..*Service.*(double,double))..
切入点表达式运算(&& || !)
@Pointcut("execution(..) || execution(..)")
2. 示例代码：
Performer.java 演员接口
public interface Performer {
public void show();
}
Singer.java 接口实现
public class Singer implements Performer {
public void show() {
System.out.println("其实我是个演员!");
// String str = null ;
// str.toString();
}
}
Audience.java 观众类， 即通知类
package cn.itcast.spring.aop.aspectj;
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.DeclareParents;
import org.aspectj.lang.annotation.Pointcut;
/**
* 观众， 需要添加 @Aspect
*/
@Aspect
public class Audience {
/**
* 引入通知,
*/
@DeclareParents(value="cn.itcast.spring.aop.aspectj.Singer",defaultImpl=ModifyDateImpl.class)
private ModifyDate md ;
/**
* 定义在切入点， 切入点表达式
*/
//任意返回值 Performer中 任意方法 任意参数
@Pointcut("execution(* cn.itcast.spring.aop.aspectj.Performer.*(..))")
public void perform(){
}
/**
* 坐好
*/
@Before(value="perform()")
public void takeSeat(){
System.out.println("takeSeat");
}
/**
* 关机
*/
@Before(value="perform()")
public void turnOffCellphone(JoinPoint jp){
System.out.println(jp.getSignature().getName());
System.out.println(jp.getArgs());
System.out.println(jp.getTarget());
System.out.println(jp.getThis());
System.out.println("turnOffCellphone");
}
/**
* returning:指定哪个参数接受方法的返回值
*/
@AfterReturning(pointcut="perform()",returning="ret")
public void applaud(Object ret){
System.out.println("applaud");
System.out.println("ret = " + ret);
}
/**
* 退票
* throwing:指定哪个参数接受异常信息
*/
@AfterThrowing(pointcut="perform()",throwing="e")
public void demandMoney(Exception e){
System.out.println("demandMoney");
System.out.println("出事了 " + e.getMessage());
}
@After("perform()")
public void goHome(){
System.out.println("goHome");
}
/*
* 环绕通知
*/
@Around(value="perform()")
public Object watch(ProceedingJoinPoint pjp){
try {
System.out.println("takeSeat");
System.out.println("turnOffCellphone");
Object o = pjp.proceed();
System.out.println("applaud");
return o;
} catch (Throwable e) {
System.out.println("demandMoney");
}
finally{
System.out.println("goHome");
}
return null ;
}
}
ModifyDate.java 引入通知接口
/**
* 修改日期
*/
public interface ModifyDate {
public void setModifyDate(Date date);
public Date getModifyDate();
}
ModifyDateImpl.java 引入通知实现
public class ModifyDateImpl implements ModifyDate {
private Date date ;
public Date getModifyDate() {
return date;
}
public void setModifyDate(Date date) {
this.date = date ;
}
}
aspectj.xml 配置文件
<?xml version="1.0"?>
<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-2.5.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-2.5.xsd ">
<!-- 观众通知 -->
<bean id="audience" class="cn.itcast.spring.aop.aspectj.Audience" />
<!-- 歌手 -->
<bean id="singer" class="cn.itcast.spring.aop.aspectj.Singer" />
<!-- 使用aspectj自动产生代理 -->
<aop:aspectj-autoproxy />
</beans>
App.java 测试代码
public class App {
public static void main(String[] args) {
ApplicationContext ac = new ClassPathXmlApplicationContext(
"cn/itcast/spring/aop/aspectj/aspectj.xml");
Performer p = (Performer) ac.getBean("singer");
p.show();
//测试引入通知
((ModifyDate)p).setModifyDate(new Date());
System.out.println(((ModifyDate)p).getModifyDate());
}
}
3. 使用pojo+xml开发aop
基于注解的aspectj声明优先于xml配置.基于xml的配置是spring专有的.aspectj得到越来越多的支持,具备更好的重用性.
其他bean 和 通知类 都不会改变， 只会不再需要用注解， 改用xml文件
pojo.xml 引入通知， 前置 后置 异常通知
<?xml version="1.0"?>
<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-2.5.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-2.5.xsd ">
<!-- 观众 -->
<bean id="audience" class="cn.itcast.spring.aop.pojo.Audience" />
<!-- 歌手 -->
<bean id="singer" class="cn.itcast.spring.aop.pojo.Singer" />
<!-- aop配置 -->
<aop:config>
<aop:aspect ref="audience">
<!-- 引入通知 -->
<aop:declare-parents types-matching="cn.itcast.spring.aop.pojo.Singer"
implement-interface="cn.itcast.spring.aop.pojo.ModifyDate"
default-impl="cn.itcast.spring.aop.pojo.ModifyDateImpl"/>
<!-- 单独定义切入点表达式 -->
<aop:pointcut id="audiencePointcut" expression="execution(* cn.itcast.spring.aop.pojo.Performer.*(..))"/>
<!-- 前置通知 -->
<aop:before method="takeSeat" pointcut-ref="audiencePointcut" />
<aop:before method="turnOffCellphone" pointcut-ref="audiencePointcut"/>
<!-- 后置通知,ret指定哪个参数接受返回值 -->
<aop:after-returning method="applaud" pointcut-ref="audiencePointcut" returning="ret"/>
<!-- throwing:指定哪个参数接受异常信息 -->
<aop:after-throwing method="demandMoney" pointcut-ref="audiencePointcut" throwing="ex"/>
<!-- -->
<aop:after method="goHome" pointcut-ref="audiencePointcut"/>
</aop:aspect>
</aop:config>
</beans>
pojoAround.xml 环绕通知
<?xml version="1.0"?>
<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-2.5.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-2.5.xsd ">
<!-- 观众 -->
<bean id="audience" class="cn.itcast.spring.aop.pojo.AudienceAround" />
<!-- 歌手 -->
<bean id="singer" class="cn.itcast.spring.aop.pojo.Singer" />
<!-- aop配置 -->
<aop:config>
<aop:aspect ref="audience">
<aop:around method="watch" pointcut="execution(* cn.itcast.spring.aop.pojo.Performer.*(..))"/>
</aop:aspect>
</aop:config>
</beans>