Spring 註解實現 AOP：從 Maven 配置到切面測試完整指南

Spring 註解驅動 AOP 開發實戰

本文將帶你完整走一遍 Spring 基於註解的 AOP 開發流程，涵蓋 Maven 依賴管理、核心業務類編寫、切面定義、XML 配置啟用以及 JUnit 測試驗證。適合初學者快速掌握 Spring AOP 核心概念與實踐。

一、專案依賴管理 (pom.xml)

使用 Maven 管理專案，核心依賴包含 Spring Context、AspectJ、AOP Alliance 及 JUnit：

<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.dzg</groupId>
  <artifactId>spring_study</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion>
  </properties>
  <dependencies>
    <!-- Spring 核心容器 -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>4.3.2.RELEASE</version>
    </dependency>
    <!-- AspectJ 運行時與織入器 -->
    <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>
    <!-- AOP Alliance 標準介面 -->
    <dependency>
      <groupId>aopalliance</groupId>
      <artifactId>aopalliance</artifactId>
      <version>1.0</version>
    </dependency>
    <!-- 測試框架 -->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
    </dependency>
  </dependencies>
</project>

二、領域模型與業務層

1. 實體類 User

package com.dzg.spring.model;

public class User {
    private int id;
    private String username;
    private String password;
    // 省略 getter/setter
}

2. DAO 介面與實現

// UserDAO.java
package com.dzg.spring.dao;
import com.dzg.spring.model.User;
public interface UserDAO {
    void save(User user);
}

// UserDAOImpl.java
package com.dzg.spring.dao.impl;
import org.springframework.stereotype.Component;
import com.dzg.spring.dao.UserDAO;
import com.dzg.spring.model.User;

@Component("u")
public class UserDAOImpl implements UserDAO {
    @Override
    public void save(User user) {
        System.out.println("user saved!");
    }
}

3. Service 層

package com.dzg.spring.service;
import javax.annotation.Resource;
import org.springframework.stereotype.Component;
import com.dzg.spring.dao.UserDAO;
import com.dzg.spring.model.User;

@Component
public class UserService {
    private UserDAO userDAO;

    public void add(User user) {
        userDAO.save(user);
    }

    @Resource(name = "u")
    public void setUserDAO(UserDAO userDAO) {
        this.userDAO = userDAO;
    }
}

三、切面類定義

使用 @Aspect 標識切面，@Before 定義前置通知，針對 UserDAOImpl.save 方法切入：

package com.dzg.spring.aop;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;

@Aspect
@Component("log")
public class LogInterceptor {
    @Before("execution(public void com.dzg.spring.dao.impl.UserDAOImpl.save(com.dzg.spring.model.User))")
    public void beforeMethod() {
        System.out.println("save start!");
    }
}

四、Spring 容器配置 (beans.xml)

啟用註解掃描與 AspectJ 自動代理：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="https://www.springframework.org/schema/beans"
       xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="https://www.springframework.org/schema/context"
       xmlns:aop="https://www.springframework.org/schema/aop"
       xsi:schemaLocation="
         https://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
         https://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd
         https://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop.xsd">

    <context:annotation-config/>
    <context:component-scan base-package="com.dzg.spring"/>
    <aop:aspectj-autoproxy/>
</beans>

五、JUnit 整合測試

package com.dzg.spring.service;
import org.junit.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.dzg.spring.model.User;

public class UserServiceTest {
    @Test
    public void testAdd() throws Exception {
        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");
        UserService service = (UserService) ctx.getBean("userService");
        System.out.println(service.getClass()); // 觀察代理類類型
        User u = new User();
        u.setUsername("zhangsan");
        u.setPassword("zhangsan");
        service.add(u);
        ctx.close();
    }
}

六、執行結果分析

class com.dzg.spring.service.UserService$$EnhancerBySpringCGLIB$$21c652e7
save start!
user saved!

控制台輸出顯示 Spring 使用 CGLIB 為 UserService 生成了代理類，切面邏輯 save start! 在目標方法執行前成功織入，驗證 AOP 配置生效。

七、總結

• Maven 引入 aspectjweaver 是啟用 @AspectJ 註解的關鍵。
• <aop:aspectj-autoproxy/> 開啟自動代理，容器會掃描 @Aspect Bean 並生成代理。
• 切入點表達式精確匹配目標方法簽名，實現關注點分離。

完整示例代碼結構清晰，可直接作為 Spring AOP 註解開發的參考模板。