spring框架应用系列三:切面编程(带参数)
切面编程(带参数)
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解决问题
1、分离业务监控与业务处理。简单点说,让开发人员更专注业务逻辑开发,类似于打印日志、统计时间、监控等等独立成一个单独的类,在需要的时候,动态的将代码切入到类的指定方法上,使方法拥有更强大的功能;
2、解决代码重复性,降低代码复杂程度;
内容说明
1、通过@Component注解,扫描(Magician)bean并注册到spring容器中时,需在XML配置文件中引入 <context:component-scan base-package="com.spring.example.aspectArgs"/>;
2、明确切面、切点、通知概念,这里切面是Magician,切点是Volunteer的thinkOfSomething方法,通知是Magician中所包含方法,由xml或注解配置,下面会分别给出示例;
3、通过执行Volunteer的thinkOfSomething方法,从而执行Magician中相应的方法,达到通知的效果;
应用实例:截听志愿者内心真实想法
先列出相关接口以及类代码
切面实现接口MindReader(读心者)
package com.spring.example.aspectAspectJArgs; //读心者 public interface MindReader { void interceptThoughts(String thoughts); void getConclusion(String thoughts); }
切点类志愿者实现接口Thinker
package com.spring.example.aspectAspectJArgs; /** * 读心者赋予一个他需要截听内心感应的志愿者 */ public interface Thinker { void thinkOfSomething(String thoughts); }
志愿者实体类Volunteer
package com.spring.example.aspectAspectJArgs; import org.springframework.stereotype.Component; /** * Created by weixw on 2017/10/24. */ @Component public class Volunteer implements Thinker { private String thoughts; @Override public void thinkOfSomething(String thoughts) { this.thoughts = thoughts; } }
以下有两种方式实现此实例的切面编程:一、通过XML配置文件,二、AspectJ注解方式
其他代码都相同,不同处在spring 的xml配置文件以及切面类文件
一、通过XML配置文件:
切面(读心者)实体类
package com.spring.example.aspectArgs; /** * Created by weixw on 2017/10/24. */ import org.springframework.stereotype.Component; /** * 截听志愿者的内心感应和显示他们在想什么 */ @Component public class Magician implements MindReader { @Override public void interceptThoughts(String thoughts) { System.out.println("Intercepting volunteer's thoughts :" +thoughts); } @Override public void getConclusion(String thoughts) { System.out.println("For your thoughts :" +thoughts); System.out.println("I think you are right."); } }
spring 配置文件 aspect-args.xml
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<?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" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <context:component-scan base-package="com.spring.example.aspectArgs"/> <aop:config> <!--通过component-scan自动扫描,@Component注解将Magician注册到spring容器--> <aop:aspect ref="magician"> <aop:pointcut id="thinking" expression="execution(* com.spring.example.aspectArgs.Thinker.thinkOfSomething(String)) and args(thoughts)"/> <aop:before pointcut-ref="thinking" method="interceptThoughts" arg-names="thoughts"/> <aop:after pointcut-ref="thinking" method="getConclusion" arg-names="thoughts"/> </aop:aspect> </aop:config> </beans>
二 、AspectJ注解方式
切面(读心者)实体类
package com.spring.example.aspectAspectJArgs; /** * Created by weixw on 2017/10/24. */ import org.aspectj.lang.annotation.AfterReturning; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Before; import org.aspectj.lang.annotation.Pointcut; import org.springframework.stereotype.Component; /** * 截听志愿者的内心感应和显示他们在想什么 */ @Component @Aspect public class Magician implements MindReader { @Pointcut("execution(* com.spring.example.aspectAspectJArgs.Thinker.thinkOfSomething(String)) " + "&& args(thoughts)") //定义切点 public void thinkOfSomething(String thoughts){} @Before("thinkOfSomething(thoughts)") @Override public void interceptThoughts(String thoughts) { System.out.println("Intercepting volunteer's thoughts :" +thoughts); } @AfterReturning("thinkOfSomething(thoughts)") @Override public void getConclusion(String thoughts) { System.out.println("For your thoughts :" +thoughts); System.out.println("I think you are right."); } }
spring 配置文件 aspect-aspectJArgs.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" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <context:component-scan base-package="com.spring.example.aspectAspectJArgs"/> <aop:aspectj-autoproxy/> </beans>
测试代码
注解测试代码如下,配置文件测试代码只需将配置文件名称改成spring/aspect-args.xml即可
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package com.spring.example.aspectAspectJArgs;/** * Created by weixw on 2017/10/19. */ import javafx.application.Application; import javafx.stage.Stage; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Driver extends Application { public static void main(String[] args) { launch(args); } @Override public void start(Stage primaryStage) { try { ApplicationContext ctx = new ClassPathXmlApplicationContext("spring/aspect-aspectJArgs.xml"); Thinker thinker = (Thinker) ctx.getBean("volunteer"); thinker.thinkOfSomething("I'm stupid."); }catch (Exception e){ e.printStackTrace(); } } }
运行结果
总结
上述列出配置文件和注解两种方式都能实现切面编程。但对于自身业务开发,个人觉得注解方式较好,因为在修改某一切面类时不需要多处修改;
本文描述可能有不对或不全之处,欢迎大家吐槽!
不要让懒惰占据你的大脑,不要让妥协拖垮你的人生。青春就是一张票,能不能赶上时代的快车,你的步伐掌握在你的脚下。