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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<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
</dependency>

2.攔截規則的註解

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@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Action {
String name();
}

2.註解的被攔截類

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@Service
public class DemoAnnotationService {
@Action(name = "註解式攔截的add操作")
public void add() {
System.out.println("======DemoAnnotationService方法add()=========");
}
}

3.方法規則被攔截類

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@Service
public class DemoMethodService {
public String add() throws Exception{
System.out.println("======DemoMethodService方法add()=========");
int i=100/0;
return "SUCCESS";
}
}

4.編寫切面

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@Aspect
@Component
public class LogAspect {
@Pointcut("@annotation(com.gemdale.gmap.spring.boot.demo.Action)")
public void annotationPointCut() {
}
@After("annotationPointCut()")
public void after(JoinPoint joinPoint) {
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
Method method = signature.getMethod();
Action action = method.getAnnotation(Action.class);
System.out.println("註解式攔截 " + action.name());
}
@Before("execution(* com.gemdale.gmap.spring.boot.demo.DemoMethodService.*(..))")
public void methodBefore(JoinPoint joinPoint) {
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
Method method = signature.getMethod();
System.out.println("before方法規則式攔截 " + method.getName());
}
@After("execution(* com.gemdale.gmap.spring.boot.demo.DemoMethodService.*(..))")
public void methodAfter(JoinPoint joinPoint) {
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
Method method = signature.getMethod();
System.out.println("after方法規則式攔截 " + method.getName());
}
@AfterReturning(pointcut = "execution(* com.gemdale.gmap.spring.boot.demo.DemoMethodService.*(..))", returning = "result")
public void methodAfterResult(JoinPoint joinPoint, Object result) {
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
Method method = signature.getMethod();
System.out.println("after result方法規則式攔截 " + method.getName() + "result=" + result);
}
@AfterThrowing(pointcut = "execution(* com.gemdale.gmap.spring.boot.demo.DemoMethodService.*(..))", throwing = "e")
public void methodAfterException(JoinPoint joinPoint, Exception e) {
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
Method method = signature.getMethod();
System.out.println("after exception方法規則式攔截 " + method.getName() + " e=" + e.getMessage());
}
}

5.配置類

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@Configuration
@ComponentScan("com.gemdale")
@EnableAspectJAutoProxy
public class AppliactionConfig {
}

6.執行類

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public class Start {
public static void main(String[] args) throws Exception{
AnnotationConfigApplicationContext configApplicationContext = new AnnotationConfigApplicationContext(
AppliactionConfig.class);
// UseFunctionService
// useFunctionService=configApplicationContext.getBean(UseFunctionService.class);
// System.out.println(useFunctionService.sayHello("Gengchong"));
DemoAnnotationService demoAnnotationService = configApplicationContext.getBean(DemoAnnotationService.class);
DemoMethodService demoMethodService = configApplicationContext.getBean(DemoMethodService.class);
demoAnnotationService.add();
demoMethodService.add();
configApplicationContext.close();
}
}

Java 面向切面程式設計AOP

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