After Throwing advice in Spring AOP – @AfterThrowing

简介

匹配的方法通过抛出异常完成/中止其执行后调用抛出通知之后。您已经知道，这种匹配方法的名称是 Joinpoint。您可以使用 @AfterThrowing 注释声明 After throwing advice。

您已经了解了上一篇文章中列出的 5 种建议类型，如下所示。

• Before advice – @Before
• After returning – @AfterReturning
• After throwing – @AfterThrowing
• After (finally) advice – @After
• Around advice – @Around

After throwing advice execution

您可以声明一个 After throwing 通知，如下所示。或者，您可以获取方法执行引发的异常和 Joinpoint 详细信息。

package com.jbd.saop.after.aspect;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.stereotype.Service;
@Service
@Aspect
public class AllAfterAspects {
  @AfterThrowing(
      pointcut = "execution(* c.jbd.saop.at.dao.*.*(..))",
      throwing = "exception")
  public void logDaoExceptions(JoinPoint joinPoint, RuntimeException exception) {
    System.out.println("Exception at: " + joinPoint.getSignature().toShortString());
    System.out.println("Exception details: " + exception);
  }
}

抛出子句还将匹配限制为仅抛出指定类型异常的那些方法执行。在这种情况下，它是 RuntimeException。

After throwing advice示例 – @AfterThrowing

问题陈述——假设我们有一个用户管理应用程序。我们想要记录方法抛出的所有异常。我们将使用上一篇文章中的相同示例，并将空值传递给 add() 和 delete() 方法。

步骤 1：添加依赖项

<dependencies>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-core</artifactId>
      <version>5.2.2.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>5.2.2.RELEASE</version>
    </dependency>
    <!-- Step-1 Add the dependencies -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-aop</artifactId>
      <version>5.2.2.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.aspectj</groupId>
      <artifactId>aspectjweaver</artifactId>
      <version>1.9.5</version>
    </dependency>
<dependencies>

步骤 2：创建用户存储库

我们将切面应用到 DAO 类。所以我们创建了示例代码——UserRepository 和 Java 配置来注册这个类，如下所示。正如我们之前讨论过的，注解@EnableAspectJAutoProxy 用于启用Spring-AOP。

UserRepository.java

package c.jbd.saop.at.dao;
import org.springframework.stereotype.Repository;
//A very stupid demo repository
@Repository
public class UserRepository {
  //Add a user
  public UserRepository add(String username){
    if(username == null) {
      throw new RuntimeException("username is null", new NullPointerException());
    }
    System.out.println("New user added: " + username);
    return this;
  }
  //Update an user
  public UserRepository update(String username, String email) {
    System.out.println("Update email: " + email);
    return this;
  }
  //Delete an user
  public boolean delete(String username){
    if (username == null) {
      throw new RuntimeException("username is null", new NullPointerException());
    }
    System.out.println("User deleted: " + username);
    return true;
  }
}

ApplicationConfig.java

package c.jbd.saop.at;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
@Configuration
@EnableAspectJAutoProxy
@ComponentScan("c.jbd.saop.at")
public class ApplicationConfig {
}

步骤 3：创建切入点表达式和通知

切入点表达式与所有 Dao 类方法匹配。如果 Dao 类方法中的任何一个抛出 RuntimeException，它将与这个切面进行匹配，并执行 logDaoExceptions() 中的代码。

package c.jbd.saop.at.aspect;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.context.annotation.Configuration;
@Configuration
@Aspect
public class ExceptionAspect {
  /**
   * Match with all dao methods.
   */
  @AfterThrowing(
      pointcut = "execution(* c.jbd.saop.at.dao.*.*(..))",
      throwing = "exception")
  public void logDaoExceptions(JoinPoint joinPoint, RuntimeException exception) {
    System.out.println("Exception at: " + joinPoint.getSignature().toShortString());
    System.out.println("Exception details: " + exception);
  }
}

第 4 步：测试示例

最后，我们将测试该示例以查看其输出。在运行测试用例之前，在 pom.xml 中添加测试依赖项。

<dependencies>
  ... 
   <!-- Test Dependencies-->
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-api</artifactId>
      <version>5.5.2</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-engine</artifactId>
      <version>5.5.2</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-test</artifactId>
      <version>5.2.2.RELEASE</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
...
<!-- Important for Jupiter-engine -->
<build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>3.0.0-M3</version>
      </plugin>
    </plugins>
  </build>
</project>

永远记得在使用 Junit-jupiter-* 时将 maven-surefire-plugin 升级到 3.0.0-M3 或更高版本。

添加测试依赖项后，在 src\test 中创建 Test 类。

package c.jbd.saop.at;
import c.jbd.saop.at.dao.UserRepository;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
@SpringJUnitConfig(ApplicationConfig.class)
public class TestAfterThrowing {
  @Autowired
  private UserRepository userRepository;
  @Test
  public void notNull() {
    Assertions.assertNotNull(userRepository);
  }
  @Test
  public void testThrows() {
    //Assert throws RuntimeException
    Assertions.assertThrows(RuntimeException.class, () -> {
      userRepository.add(null);
      userRepository.delete(null);
    });
    //Assert does not throw exception
    Assertions.assertDoesNotThrow(() -> {
      userRepository.delete("alexa");
    });
  }
}

测试用例应通过控制台中的以下输出。

我希望已经让您对@AfterThrowing – Spring AOP 中的投掷后建议有一个很好的理解。在实际用例中，您可能希望使用它对异常执行日志或分析。

After method - Exception at: UserRepository.add(..)
Exception details: java.lang.RuntimeException: username is null
User deleted: alexa