SpringAOP之注入AspectJ切面

来源：互联网发布：专业网络k歌声卡编辑：程序博客网时间：2024/06/02 00:43

写在开头：
本文参考资料为Spring In Action(第4版)，文中理解不对之处均为本人原因，与书籍无关。

Spring In Action中提到：“Spring AOP构建在动态代理之上，因此，Spring对AOP的支持局限于方法拦截”。

那么，当我们需要创建更细粒度的通知或想监测bean的创建时，Spring所支持的AOP就比较弱了，这时，可以选择使用AspectJ提供的构造器切点，并且可以借助Spring的依赖注入把bean装配进AspectJ切面中。下面就来举个栗子：

//定义表演接口package concert;public interface Performance {    void perform();     void finishPerform(String performer, String title); }

//定义钢琴表演package concert;public class PianoPerform implements Performance {    public PianoPerform(){        System.out.println("有请钢琴表演");    }    @Override    public void perform() {        System.out.println("钢琴表演开始");    }    @Override    public void finishPerform(String performer, String title) {        System.out.println(performer + "演奏钢琴曲：" + title);    }}

//定义小提琴表演package concert;public class ViolinPerform implements Performance {    public ViolinPerform(){        System.out.println("有请小提琴表演");    }    @Override    public void perform() {        System.out.println("小提琴表演开始");    }    @Override    public void finishPerform(String performer, String title){        System.out.println(performer + "演奏了小提琴曲：" + title);    }   }

//定义工作人员，将作为切面的协作beanpackage concert;public class Worker {    public void take(){        System.out.println("观众已全部交出手机");    }    public void sendMsg(String name){        System.out.println(name + "表演即将开始，请各位观众交出手机");    }    public void broadcast(String performer, String title){        System.out.println(performer + "演奏完毕，刚才演奏的曲子叫：" + title);    }}

//定义切面package concert;public aspect Audience {        private Worker worker;    public Audience(){}    //通过setter方法注入    public void setWorker(Worker worker){        this.worker = worker;        System.out.println("工作人员已入场");    }    //定义piano构造器切点和后置通知    pointcut piano():execution(concert.PianoPerform.new());    after():piano(){        worker.sendMsg("钢琴");    }    //定义violin构造器切点和后置通知    pointcut violin():execution(concert.ViolinPerform.new());    after():violin(){        worker.sendMsg("小提琴");    }    //定义不带参数方法切点和前置通知    pointcut perform():execution(* concert.Performance.perform());    before():perform(){        worker.take();    }    //定义带两个参数的切点和后置通知    pointcut finishPerform(String performer, String title):execution(* concert.Performance.finishPerform(String, String)) && args(performer, title);    after(String performer, String title):finishPerform(performer, title){        worker.broadcast(performer, title);    }}

XML配置文件：spring.xml

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">    <!--<bean id="piano" class="concert.PianoPerform" lazy-init="true"/>-->    <bean id="worker" class="concert.Worker"/>    <!--Spring需要通过静态方法aspectOf获得audience实例，Audience切面编译后的class文件附在文末-->    <bean class="concert.Audience" factory-method="aspectOf">        <property name="worker" ref="worker" /><!--通过Spring把协作的bean注入到切面中-->    </bean>    <!--这里注意一下bean的顺序，因为在构造器切点后置通知时调用了worker的sendMsg(String)方法，所以避免出现空指针异常，咱们先把worker声明在前-->    <!--如果要将piano或者violin声明在前，可以设置lazy-init="true"-->    <!--所以spring是从上到下解析并实例化bean？还是解析完整个文件再实例化呢？欢迎评论区留言交流-->    <bean id="piano" class="concert.PianoPerform"/>    <bean id="violin" class="concert.ViolinPerform"/></beans>

//主程序package concert;import org.springframework.context.support.ClassPathXmlApplicationContext;public class MainClass {    public static void main(String[] args) {        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring.xml");        Performance piano = context.getBean("piano", Performance.class);        piano.perform();        piano.finishPerform("亚莎·海菲兹", "致爱丽斯");        Performance violin = context.getBean("violin", Performance.class);        violin.perform();        violin.finishPerform("霍洛维茨", "爱之喜悦");    }}

用到的依赖：pom.xml

<dependencies>        <dependency>            <groupId>junit</groupId>            <artifactId>junit</artifactId>            <version>4.12</version>            <scope>test</scope>        </dependency>        <dependency>            <groupId>org.springframework</groupId>            <artifactId>spring-context</artifactId>            <version>4.3.8.RELEASE</version>        </dependency>        <dependency>            <groupId>org.springframework</groupId>            <artifactId>spring-core</artifactId>            <version>4.3.8.RELEASE</version>        </dependency>               <dependency>            <groupId>org.springframework</groupId>            <artifactId>spring-beans</artifactId>            <version>4.3.8.RELEASE</version>        </dependency>                <dependency>            <groupId>org.springframework</groupId>            <artifactId>spring-aop</artifactId>            <version>4.3.8.RELEASE</version>        </dependency>                <dependency>            <groupId>org.aspectj</groupId>            <artifactId>aspectjrt</artifactId>            <version>1.8.7</version>        </dependency>    </dependencies>    <build>        <plugins>        <!--编译aspect的插件，必须要将Audience.aj编译为class文件，            不然spring创建audience bean的时候找不到类-->            <plugin>                <groupId>org.codehaus.mojo</groupId>                <artifactId>aspectj-maven-plugin</artifactId>                <version>1.8</version>                <executions>                    <execution>                        <goals>                            <goal>compile</goal>                        </goals>                    </execution>                </executions>                <configuration>                    <complianceLevel>1.8</complianceLevel>                    <source>1.8</source>                    <target>1.8</target>                </configuration>            </plugin>        </plugins>    </build>

运行结果：
工作人员已入场
有请钢琴表演
钢琴表演即将开始，请各位观众交出手机
有请小提琴表演
小提琴表演即将开始，请各位观众交出手机
观众已全部交出手机
钢琴表演开始
亚莎·海菲兹演奏钢琴曲：致爱丽斯
亚莎·海菲兹演奏完毕，刚才演奏的曲子叫：致爱丽斯
观众已全部交出手机
小提琴表演开始
霍洛维茨演奏了小提琴曲：爱之喜悦
霍洛维茨演奏完毕，刚才演奏的曲子叫：爱之喜悦

Audience.class文件

package concert;import concert.Worker;import org.aspectj.lang.NoAspectBoundException;import org.aspectj.lang.annotation.After;import org.aspectj.lang.annotation.Aspect;import org.aspectj.lang.annotation.Before;@Aspectpublic class Audience {    private Worker worker;    static {        try {            ajc$postClinit();        } catch (Throwable var1) {            ajc$initFailureCause = var1;        }    }    public void setWorker(Worker worker) {        this.worker = worker;        System.out.println("工作人员已入场");    }    public Audience() {    }    @After(        value = "piano()",        argNames = ""    )    public void ajc$after$concert_Audience$1$dd71540a() {        this.worker.sendMsg("钢琴");    }    @After(        value = "violin()",        argNames = ""    )    public void ajc$after$concert_Audience$2$57c630b6() {        this.worker.sendMsg("小提琴");    }    @Before(        value = "perform()",        argNames = ""    )    public void ajc$before$concert_Audience$3$1cad9822() {        this.worker.take();    }    @After(        value = "finishPerform(performer, title)",        argNames = "performer,title"    )    public void ajc$after$concert_Audience$4$1840cdb9(String performer, String title) {        this.worker.broadcast(performer, title);    }    //Aspect提供的静态方法，返回Audience切面的一个实例，Spring即可通过factory-method属性获得该实例    //<bean class="concert.Audience" factory-method="aspectOf">    public static Audience aspectOf() {        if(ajc$perSingletonInstance == null) {            throw new NoAspectBoundException("concert_Audience", ajc$initFailureCause);        } else {            return ajc$perSingletonInstance;        }    }    public static boolean hasAspect() {        return ajc$perSingletonInstance != null;    }}

写在最后：
Spring所支持的AOP已经可以满足很多需求，如果要求更高，可以使用AspectJ提供的更丰富的切点类型，当然需要熟悉AspectJ语法。
本文只是简单的举出了部分切点类型和通知类型，更多的类型读者可以自行尝试。欢迎留言指正，感谢您的阅读！

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