Java 面向切面程式設計AOP

百聯達發表於2017-02-15
Java程式設計
一：背景
Spring的AOP的存在目的是為了解耦。AOP可以讓一組類共享相同的行為。在OOP中只能透過繼承類和實現介面，來是程式碼的耦合度增強，且類繼承只能為單繼承，阻礙更多行為新增到一組類上，AOP彌補了OPP的不足。

二：概述  Spring支援AspectJ的註解方式切面程式設計

1.使用@Aspect 宣告一個切面。

2.使用@After,@Before,@Around 定義建言（advice）,可直接將攔截規則（切點）作為引數。

3.其中@After,@Before,@Around引數的攔截規則為切點（PointCut） ,為了使切點複用，可使用@PointCut 專門定義攔截規則，然後在@After,@Before,@Around的引數中呼叫。

4.其中符合條件的每一個被攔截處為連線點（JoinPoint）

三：程式碼例項

1.pom.xml


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  1. <dependency>
  2.             <groupId>org.springframework</groupId>
  3.             <artifactId>spring-core</artifactId>
  4.         </dependency>
  5.         <dependency>
  6.             <groupId>org.springframework</groupId>
  7.             <artifactId>spring-beans</artifactId>
  8.         </dependency>

  10.         <dependency>
  11.             <groupId>org.springframework</groupId>
  12.             <artifactId>spring-context</artifactId>
  13.         </dependency>

  15.         <dependency>
  16.             <groupId>org.springframework</groupId>
  17.             <artifactId>spring-aop</artifactId>
  18.         </dependency>

  20.         <dependency>
  21.             <groupId>org.aspectj</groupId>
  22.             <artifactId>aspectjrt</artifactId>
  23.         </dependency>

  25.         <dependency>
  26.             <groupId>org.aspectj</groupId>
  27.             <artifactId>aspectjweaver</artifactId>
  28.         </dependency>
2.攔截規則的註解


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  1. @Target(ElementType.METHOD)
  2. @Retention(RetentionPolicy.RUNTIME)
  3. @Documented
  4. public @interface Action {
  5.     String name();
  6. }
2.註解的被攔截類


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  1. @Service
  2. public class DemoAnnotationService {

  4.     @Action(name = "註解式攔截的add操作")
  5.     public void add() {
  6.        System.out.println("======DemoAnnotationService方法add()=========");
  7.     }
  8. }
3.方法規則被攔截類


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  1. @Service
  2. public class DemoMethodService {
  3.     public String add() throws Exception{
  4.         System.out.println("======DemoMethodService方法add()=========");
  5.         int i=100/0;
  6.         return "SUCCESS";
  7.     }
  8. }

4.編寫切面


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  1. @Aspect
  2. @Component
  3. public class LogAspect {

  5.     @Pointcut("@annotation(com.gemdale.gmap.spring.boot.demo.Action)")
  6.     public void annotationPointCut() {
  7.     }

  9.     @After("annotationPointCut()")
  10.     public void after(JoinPoint joinPoint) {
  11.         MethodSignature signature = (MethodSignature) joinPoint.getSignature();
  12.         Method method = signature.getMethod();
  13.         Action action = method.getAnnotation(Action.class);

  15.         System.out.println("註解式攔截 " + action.name());
  16.     }

  18.     @Before("execution(* com.gemdale.gmap.spring.boot.demo.DemoMethodService.*(..))")
  19.     public void methodBefore(JoinPoint joinPoint) {
  20.         MethodSignature signature = (MethodSignature) joinPoint.getSignature();
  21.         Method method = signature.getMethod();
  22.         System.out.println("before方法規則式攔截 " + method.getName());
  23.     }

  25.     @After("execution(* com.gemdale.gmap.spring.boot.demo.DemoMethodService.*(..))")
  26.     public void methodAfter(JoinPoint joinPoint) {
  27.         MethodSignature signature = (MethodSignature) joinPoint.getSignature();
  28.         Method method = signature.getMethod();
  29.         System.out.println("after方法規則式攔截 " + method.getName());
  30.     }

  32.     @AfterReturning(pointcut = "execution(* com.gemdale.gmap.spring.boot.demo.DemoMethodService.*(..))", returning = "result")
  33.     public void methodAfterResult(JoinPoint joinPoint, Object result) {
  34.         MethodSignature signature = (MethodSignature) joinPoint.getSignature();
  35.         Method method = signature.getMethod();
  36.         System.out.println("after result方法規則式攔截 " + method.getName() + "result=" + result);
  37.     }

  39.     @AfterThrowing(pointcut = "execution(* com.gemdale.gmap.spring.boot.demo.DemoMethodService.*(..))", throwing = "e")
  40.     public void methodAfterException(JoinPoint joinPoint, Exception e) {
  41.         MethodSignature signature = (MethodSignature) joinPoint.getSignature();
  42.         Method method = signature.getMethod();
  43.         System.out.println("after exception方法規則式攔截 " + method.getName() + " e=" + e.getMessage());
  44.     }

  46. }
5.配置類


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  1. @Configuration
  2. @ComponentScan("com.gemdale")
  3. @EnableAspectJAutoProxy
  4. public class AppliactionConfig {

  6. }

6.執行類


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  1. public class Start {
  2.     public static void main(String[] args) throws Exception{

  4.         AnnotationConfigApplicationContext configApplicationContext = new AnnotationConfigApplicationContext(
  5.                 AppliactionConfig.class);
  6.         // UseFunctionService
  7.         // useFunctionService=configApplicationContext.getBean(UseFunctionService.class);
  8.         // System.out.println(useFunctionService.sayHello("Gengchong"));
  9.         DemoAnnotationService demoAnnotationService = configApplicationContext.getBean(DemoAnnotationService.class);
  10.         DemoMethodService demoMethodService = configApplicationContext.getBean(DemoMethodService.class);

  12.         demoAnnotationService.add();

  14.         demoMethodService.add();

  16.         configApplicationContext.close();
  17.     }
  18. }


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