Spring AOP（三）——通过@AspectJ注解切面
在Spring AOP（二）中给出了在XML中配置切面的方法，本节学习通过@AspectJ来注解切面，使用的例子仍然是Spring AOP（二）中的例子，前面讲的已经很详细了，具体原理不再说明，直接上代码：
1 注解切面
XML配置
<?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-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">
<aop:aspectj-autoproxy />
<bean id="drama" class="com.springinaction.aop.Drama" />
<bean id="audience" class="com.springinaction.aop.Audience" />
</beans>要点：
- 添加
<aop:aspectj-autoproxy />实现注解切面。 - 切面和切点的Bean还是需要定义。
注解切面
package com.springinaction.aop;
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;
@Aspect
public class Audience {
@Pointcut("execution(* com.springinaction.aop.Performer.perform(..))")
public void performance() {} // 定义切点
@Before("performance()")
public void takeSeats() {
// 节目开始之前
System.out.println("演出前——观众开始入座");
}
@Before("performance()")
public void turnOffCellPhones() {
// 节目开始之前
System.out.println("演出前——观众关机或静音");
}
@AfterReturning("performance()")
public void applaud() {
// 节目成功结束之后
System.out.println("演出很成功——观众鼓掌：啪啪啪");
}
@AfterThrowing("performance()")
public void demandRefund() {
// 节目表演失败之后
System.out.println("节目演出很失败——切！一点都不好看，我们要求退钱！");
}
}要点：
- 用@Aspect标注类
- 用@Pointcut标注切点
- 用@Before、@AfterReturning、@AfterThrowing标注前置、后置通知
测试类
package com.springinaction.aop;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class AudienceTest {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext(
"com/springinaction/aop/aop1.xml");
Performer drama = (Performer)ctx.getBean("drama");
drama.perform();
}
}输出结果
演出前——观众开始入座
演出前——观众关机或静音
话剧正在进行中——（重复一千次）
演出很成功——观众鼓掌：啪啪啪2 注解环绕通知
切面类的环绕通知方法
@Around("performance()")
public void watchPerformance(ProceedingJoinPoint joinpoint) {
try {
System.out.println("演出前——观众开始入座");
System.out.println("演出前——观众关机或静音");
long start = System.currentTimeMillis();
joinpoint.proceed(); // 执行被通知的方法
long end = System.currentTimeMillis();
System.out.println("演出很成功——观众鼓掌：啪啪啪");
System.out.println("演出持续了 " + (end - start) + " milliseconds");
} catch (Throwable e) {
System.out.println("节目演出很失败——切！一点都不好看，我们要求退钱！");
}
}测试类
package com.springinaction.aop;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class AudienceTest {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext(
"com/springinaction/aop/aop1.xml");
Performer drama = (Performer)ctx.getBean("drama");
drama.perform();
}
}输出结果
演出前——观众开始入座
演出前——观众关机或静音
话剧正在进行中——（重复一千次）
演出很成功——观众鼓掌：啪啪啪
演出持续了 37 milliseconds3 传递参数给注解的通知
XML配置
<?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-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">
<aop:aspectj-autoproxy />
<bean id="magician" class="com.springinaction.aop.Magician" />
<bean id="volunteer" class="com.springinaction.aop.Volunteer" />
</beans>切面
package com.springinaction.aop;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
@Aspect
public class Magician implements MindReader {
private String thoughts;
@Pointcut("execution(* com.springinaction.aop.Thinker.thinkOfSomething(String)) "
+ "&& args(thoughts)")
public void thinking(String thoughts) {}
@Before("thinking(thoughts)")
public void interceptThoughts(String thoughts) {
System.out.println("让我猜猜你在想什么？");
this.thoughts = thoughts;
System.out.println(this.getThoughts());
}
public String getThoughts() {
System.out.print("你在想：");
return thoughts;
}
}测试类
package com.springinaction.aop;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MagicianTest {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext(
"com/springinaction/aop/aop1.xml");
Thinker thinker = (Thinker) ctx.getBean("volunteer");
thinker.thinkOfSomething("你猜我在想什么？");
}
}输出结果
让我猜猜你在想什么？
你在想：你猜我在想什么？3 注解引入
注解引入所在切面
package com.springinaction.aop;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.DeclareParents;
@Aspect
public class Audience {
@DeclareParents(
value = "com.springinaction.aop.Performer+",
defaultImpl = GraciousAssist.class)
public static AssistPerformer assistPerformer;
}测试类
package com.springinaction.aop;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class AudienceTest {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext(
"com/springinaction/aop/aop1.xml");
AssistPerformer ap = (AssistPerformer) ctx.getBean("drama");
ap.assist();
}
}输出结果
GraciousAssist来助演了——OVER