Spring 之定义切面尝试（基于注解）

【Spring 之定义切面尝试】

1、标记为深红色的依赖包是必须的

            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-context</artifactId>
                <version>4.3.9.RELEASE</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-test</artifactId>
                <version>4.3.5.RELEASE</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-core</artifactId>
                <version>4.3.7.RELEASE</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-beans</artifactId>
                <version>4.3.9.RELEASE</version>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
                <scope>test</scope>
            </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>1.8.10</version>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.8.10</version>
        </dependency>

2、相对于表演定义一个观众切面。

package concert;

import org.springframework.stereotype.Component;

@Component
public class TheShow implements Performance {
    public void perform() {
        System.out.println("Doing performance!");
    }
}

package concert;

import org.aspectj.lang.annotation.*;

@Aspect
public class Audience {

    @Pointcut("execution(* concert.Performance.perform(..))")
    public void performance() {}

    @Before("performance()")
    public void silenceCellPhones() {
        System.out.println("silencing cell phones");
    }

    @Before("performance()")
    public void takeSeats() {
        System.out.println("Taking seats");
    }

    @AfterReturning("performance()")
    public void applause() {
        System.out.println("CLAP CLAP CLAP!!!");
    }

    @AfterThrowing("performance()")
    public void demandRefund() {
        System.out.println("Demanding a refund");
    }
}

等价的环绕通知：

package concert;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;

@Aspect
public class Audience {

    @Pointcut("execution(* concert.Performance.perform(..))")
    public void performance() {}

    @Around("performance()")
    public void watchPerformance(ProceedingJoinPoint jp) {
        try {
            System.out.println("Silencing cell phones");
            System.out.println("Taking seats");
            jp.proceed();
            System.out.println("CLAP CLAP CLAP!!!");
        } catch (Throwable e) {
            System.out.println("Demanding a refund");
        }
    }
}

3、启用 AspectJ 注解的自动代理有两种方式：JavaConfig 和 XML

package concert;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;

@Configuration
@EnableAspectJAutoProxy
@ComponentScan
public class ConcertConfig {

    @Bean
    public Audience audience() {
        return new Audience();
    }

}

<?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:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

    <context:component-scan base-package="concert" />

    <aop:aspectj-autoproxy />

    <bean class="concert.Audience" />

</beans>

启用 AspectJ 注解的自动代理的结果是：这个代理会围绕着所有该切面切点所匹配的 bean （关于代理书上有个特别形象的图片）

4、测试切面

package concert;

import static org.junit.Assert.*; 
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = ConcertConfig.class)
public class TheShowTest {

    @Autowired
    Performance theShow;

    @Test
    public void theShowShouldNotBeNull() {
        assertNotNull(theShow);
    }

    @Test
    public void test() {
        theShow.perform();
    }
}