Spring AOP @Aspect support annotation

还是这个例子，我们用完全annotation的方法来实现。代码我就不重复了，跟前面XML配置是同一套。
修改配置文件：

<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"> <!-- Configure Target Objects --> <bean id="zoo" class="com.edi.poc.Zoo"> <constructor-arg value="People"/> </bean> <bean id="dinoHall" class="com.edi.poc.DinoHall"/> <bean id="jack" class="com.edi.poc.Tourer"> <constructor-arg value="Jack"/> </bean> <bean id="myAspect" class="com.edi.poc.aop.MyAspect"/> <aop:aspectj-autoproxy/> </beans>

修改Aspect类

@Aspect public class MyAspect { @Before("execution(* com.edi.poc.Zoo.enter(..))") public void before(JoinPoint joinPoint) { System.out.println("Before method..."); Statistic.increaseTotalTraffic(); } @After("execution(* com.edi.poc.ifc.Hall.visit(..))") public void after(JoinPoint joinPoint) { System.out.println("After return..."); Statistic.increaseIncome(HALL_NAME.DINOSAUR, BigDecimal.valueOf(2l)); } }

运行，输出为：
Dinosaur hall is opened.
The People Zoo is opened.
Before method...
Charge Jack $1.00 for ticket.
Jack needs to be charged first.
Dianosaur hall charges Jack $2.00
Jack visited diano hall.
After return...
Current traffic: 1
Income of DINOSAUR: ￥2.00
Dinosaur hall is closed.
The People Zoo is closed.

一模一样。而且更加简单了。世界如此美好~如此清净……

可以看到用annotation来做AOP，实在是简单的不得了。这里唯一没有摆脱XML的，就是Spring的容器的配置文件。当然，Spring这段配置也可以完全用annotation来做，这样就完全不要applicationContext.xml这个文件了。参考如下步骤：

先把Main类改改，让它支持配置

@ComponentScan @Configuration @EnableAspectJAutoProxy public class Main { …. }

这里@ComponentScan是为了让Spring自动识别
@Configuration是让该类变成配置类
@EnableAspectJAutoProxy是启动AutoProxy

将几个让Spring自己加载的类变成Component，Spring可以自动识别加载

@Component public class Zoo { … } @Component public class DinoHall implements Hall { … } @Aspect @Component public class MyAspect { … }

如果不想让Spring来管理，可以在原类里面把@Component去掉，然后在Main类里面加上

public class Main { @Bean(name="dinoHall") public Hall getDinoHall() { return new DinoHall(); } }

这样就可以通过ctx.getBean("dinoHall")
来获得实例。

最终修改调用过程如下：

public static void main(String[] args) { ApplicationContext ctx = new AnnotationConfigApplicationContext(Main.class); Zoo zoo = (Zoo) ctx.getBean(Zoo.class); zoo.init("People"); Hall dinoHall = (Hall)ctx.getBean("dinoHall"); zoo.addHall(HALL_NAME.DINOSAUR, dinoHall); Tourer jack = new Tourer("Jack"); zoo.open(); jack.visit(zoo, HALL_NAME.DINOSAUR); System.out.println("Current traffic: " + Statistic.getTotalTraffic()); NumberFormat currency = NumberFormat.getCurrencyInstance(); System.out.println("Income of " + HALL_NAME.DINOSAUR + ": "+ currency.format(Statistic.getIncome(HALL_NAME.DINOSAUR))); zoo.close(); }

输出：

Dinosaur hall is opened.

The People Zoo is opened.

Before method...

Charge Jack $1.00 for ticket.

Jack needs to be charged first.

Dianosaur hall charges Jack $2.00

Jack visited diano hall.

After return...

Current traffic: 1

Income of DINOSAUR: ￥2.00

Dinosaur hall is closed.

The People Zoo is closed.

总结

完全的annotation是非常方便的，就像ejb。但是，Spring的annotation做的还不是非常的完善，有些地方还需要提高。例如，在

Hall dinoHall = (Hall)ctx.getBean("dinoHall");
这里，我们如果不定义

@Bean(name="dinoHall")

public Hall getDinoHall()

{

return new DinoHall();

}
在DinoHall上加上@Component后，用
Hall dinoHall = (Hall)ctx.getBean(Hall.class);
来获得实例，这里有个问题就是，后面传参的class，如果该类实现了接口，必须得传入其接口才行，否则就会报异常：
org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.edi.poc.DinoHall] is defined
这个我怀疑是因为Spring的容器智能的选择了JDK的动态代理来反射生成实际类，而JDK的动态代理要求Target必须实现接口。理论上改成强制CGLIB应该能解决问题，但是我找了下，并没找到如何用annotation来标示强制使用CGLIB……

还例如，Spring3现在支持JSR-250定义的@PostConsturct等生命周期管理的注解，但是，我也没有找到如何使用annotation来启用。网上和官方文档都是给出了修改配置文件来使其支持。

本文源码：
https://github.com/EdisonXu/POC/tree/master/intro-aop