# Spring AOP AspectJ `@Before`注解示例 > 原文： [https://howtodoinjava.com/spring-aop/aspectj-before-annotation-example/](https://howtodoinjava.com/spring-aop/aspectj-before-annotation-example/) 在這個 Spring aop 示例中，我們將學習使用 Aspectj `@Before`注解。 `@Before`帶注解的方法恰好在所有與切入點表達式匹配的方法之前運行。 在此示例中，我們將創建簡單的 spring 應用程序，添加日志記錄切面，然后基于在`@Before`注解中傳遞的切入點信息來調用切面方法。 ## AspectJ `@Before`注解的用法 您可以按以下方式使用`@Before`注解。 ```java @Aspect public class LoggingAspect { @Before("execution(* com.howtodoinjava.app.service.impl.EmployeeManagerImpl.*(..))") public void logBeforeAllMethods(JoinPoint joinPoint) { ... } @Before("execution(* com.howtodoinjava.app.service.impl.EmployeeManagerImpl.getEmployeeById(..))") public void logBeforeGetEmployee(JoinPoint joinPoint) { ... } } ``` ## 項目結構  Spring AOP 項目結構 ## Spring AOP AspectJ Maven 依賴關系 我添加了 spring core，spring aop 和 Aspectj 依賴項。 ```java <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd; <modelVersion>4.0.0</modelVersion> <groupId>com.howtodoinjava</groupId> <artifactId>SpringAOPExamples</artifactId> <version>0.0.1-SNAPSHOT</version> <name>Spring AOP Examples</name> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>4.3.2.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context-support</artifactId> <version>4.3.2.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-aop</artifactId> <version>4.3.2.RELEASE</version> </dependency> <dependency> <groupId>org.aspectj</groupId> <artifactId>aspectjrt</artifactId> <version>1.8.9</version> </dependency> <dependency> <groupId>org.aspectj</groupId> <artifactId>aspectjweaver</artifactId> <version>1.8.9</version> </dependency> </dependencies> </project> ``` ## 啟用 AspectJ 支持 在 XML 配置文件中，您可以添加`aop:aspectj-autoproxy`元素以啟用`@AspectJ`注解支持。 ```java <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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd "> <!-- Enable @AspectJ annotation support --> <aop:aspectj-autoproxy /> <!-- Employee manager --> <bean id="employeeManager" class="com.howtodoinjava.app.service.impl.EmployeeManagerImpl" /> <!-- Logging Aspect --> <bean id="loggingAspect" class="com.howtodoinjava.app.aspect.LoggingAspect" /> </beans> ``` ## 需要執行切面的服務方法 `EmployeeManager.java`和`EmployeeManagerImpl.java` ```java public interface EmployeeManager { public EmployeeDTO getEmployeeById(Integer employeeId); public List<EmployeeDTO> getAllEmployee(); public void createEmployee(EmployeeDTO employee); public void deleteEmployee(Integer employeeId); public void updateEmployee(EmployeeDTO employee); } public class EmployeeManagerImpl implements EmployeeManager { public EmployeeDTO getEmployeeById(Integer employeeId) { System.out.println("Method getEmployeeById() called"); return new EmployeeDTO(); } public List<EmployeeDTO> getAllEmployee() { System.out.println("Method getAllEmployee() called"); return new ArrayList<EmployeeDTO>(); } public void createEmployee(EmployeeDTO employee) { System.out.println("Method createEmployee() called"); } public void deleteEmployee(Integer employeeId) { System.out.println("Method deleteEmployee() called"); } public void updateEmployee(EmployeeDTO employee) { System.out.println("Method updateEmployee() called"); } } ``` ## 編寫 AspectJ 注解的類和方法 用切入點信息編寫 aspectj 注解的類和方法。 ```java @Aspect public class LoggingAspect { @Before("execution(* com.howtodoinjava.app.service.impl.EmployeeManagerImpl.*(..))") public void logBeforeAllMethods(JoinPoint joinPoint) { System.out.println("****LoggingAspect.logBeforeAllMethods() : " + joinPoint.getSignature().getName()); } @Before("execution(* com.howtodoinjava.app.service.impl.EmployeeManagerImpl.getEmployeeById(..))") public void logBeforeGetEmployee(JoinPoint joinPoint) { System.out.println("****LoggingAspect.logBeforeGetEmployee() : " + joinPoint.getSignature().getName()); } @Before("execution(* com.howtodoinjava.app.service.impl.EmployeeManagerImpl.createEmployee(..))") public void logBeforeCreateEmployee(JoinPoint joinPoint) { System.out.println("****LoggingAspect.logBeforeCreateEmployee() : " + joinPoint.getSignature().getName()); } } ``` ## 測試 Spring AspectJ 的配置和執行 現在，我們來測試以上配置的切面是否在給定的切入點信息上執行。 ```java import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.howtodoinjava.app.model.EmployeeDTO; import com.howtodoinjava.app.service.EmployeeManager; public class TestMain { @SuppressWarnings("resource") public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); EmployeeManager manager = (EmployeeManager) context.getBean("employeeManager"); manager.getEmployeeById(1); manager.createEmployee(new EmployeeDTO()); } } ``` ```java ****LoggingAspect.logBeforeAllMethods() : getEmployeeById ****LoggingAspect.logBeforeGetEmployee() : getEmployeeById Method getEmployeeById() called ****LoggingAspect.logBeforeAllMethods() : createEmployee ****LoggingAspect.logBeforeCreateEmployee() : createEmployee Method createEmployee() called ``` 顯然，在相關聯的關節上執行切面建議。 學習愉快！ 參考文獻： [Spring AOP 參考](https://docs.spring.io/spring/docs/current/spring-framework-reference/html/aop.html) [`@Before`注解](https://eclipse.org/aspectj/doc/next/aspectj5rt-api/org/aspectj/lang/annotation/Before.html) [`@Aspect`注解](https://eclipse.org/aspectj/doc/next/aspectj5rt-api/org/aspectj/lang/annotation/Aspect.html) [AspectJ 注解配置示例](https://howtodoinjava.com/spring/spring-aop/spring-aop-aspectj-example-tutorial-using-annotation-config/) [不同切入點表達式以及示例](https://howtodoinjava.com/spring/spring-aop/writing-spring-aop-aspectj-pointcut-expressions-with-examples/)