Spring源码分析之事件机制——观察者模式（三）

自定义事件

事件监听器

事件发布者（服务层）

使用示例controller层

Spring源码分析之事件机制——观察者模式（一）-CSDN博客

Spring源码分析之事件机制——观察者模式（二）-CSDN博客

这两篇文章是这个篇章的前篇，感兴趣的读者可以阅读一下，从spring源码分析观察者模式

接下来说明一下Spring事件机制使用案例，就一个模拟用户注册场景的场景吧，事件机制其实还可以运用到更加广泛的作用。

说实话，个人感觉Spring事件机制真的好用。

自定义事件

java">public class UserRegisteredEvent extends ApplicationEvent {private final String username;private final String email;private final LocalDateTime registeredTime;public UserRegisteredEvent(Object source, String username, String email) {super(source);this.username = username;this.email = email;this.registeredTime = LocalDateTime.now();}// getter方法public String getUsername() {return username;}public String getEmail() {return email;}public LocalDateTime getRegisteredTime() {return registeredTime;}
}

事件监听器

java">@Component
@Order(1)  // 定义监听器执行顺序
public class EmailNotificationListener implements ApplicationListener<UserRegisteredEvent> {private final EmailService emailService;@Autowiredpublic EmailNotificationListener(EmailService emailService) {this.emailService = emailService;}@Overridepublic void onApplicationEvent(UserRegisteredEvent event) {// 发送欢迎邮件emailService.sendWelcomeEmail(event.getEmail(), event.getUsername());log.info("Welcome email sent to user: {}", event.getUsername());}
}

java">@Component
@Order(2)
public class UserCacheListener implements ApplicationListener<UserRegisteredEvent> {private final CacheManager cacheManager;@Autowiredpublic UserCacheListener(CacheManager cacheManager) {this.cacheManager = cacheManager;}@Overridepublic void onApplicationEvent(UserRegisteredEvent event) {// 更新用户缓存cacheManager.putUserCache(event.getUsername());log.info("User cache updated for: {}", event.getUsername());}
}

事件发布者（服务层）

java">@Service
@Transactional
public class UserService {private final UserRepository userRepository;private final ApplicationEventPublisher eventPublisher;@Autowiredpublic UserService(UserRepository userRepository, ApplicationEventPublisher eventPublisher) {this.userRepository = userRepository;this.eventPublisher = eventPublisher;}public User registerUser(String username, String email, String password) {// 验证用户数据validateUserData(username, email, password);// 创建用户User user = new User(username, email, password);user = userRepository.save(user);// 发布用户注册事件eventPublisher.publishEvent(new UserRegisteredEvent(this, username, email));log.info("User registered and event published: {}", username);return user;}private void validateUserData(String username, String email, String password) {// 数据验证逻辑}
}

使用示例controller层

java">@RestController
@RequestMapping("/api/users")
public class UserController {private final UserService userService;@Autowiredpublic UserController(UserService userService) {this.userService = userService;}@PostMapping("/register")public ResponseEntity<UserDTO> registerUser(@RequestBody UserRegistrationRequest request) {User user = userService.registerUser(request.getUsername(),request.getEmail(),request.getPassword());return ResponseEntity.ok(UserDTO.fromUser(user));}
}

用户注册时，UserService发布UserRegisteredEvent事件，EmailNotificationListener同步处理邮件发送，UserCacheListener同步更新缓存，AsyncAnalyticsListener异步处理统计数据，通过@Order注解控制监听器执行顺序。

这种实现方式将用户注册的核心逻辑与后续的处理操作解耦，使得系统更容易维护和扩展。每个监听器都专注于自己的职责，可以独立地添加、移除或修改，而不会影响其他部分的代码。