Java Spring ApplicationEvent 代码示例解析

@Getter
public static final class ImportedKnowledgeEvent extends ApplicationEvent {
    private final Knowledge knowledge;
    private final KWDocument document;
    // 构造器1：只有knowledge
    public ImportedKnowledgeEvent(Object source, Knowledge knowledge) {
        super(source);
        this.knowledge = knowledge;
        this.document = null;
    }
    // 构造器2：knowledge + document
    public ImportedKnowledgeEvent(Object source, Knowledge knowledge, KWDocument document) {
        super(source);
        this.knowledge = knowledge;
        this.document = document;
    }
}

@Service
public class KnowledgeService {
    @Autowired
    protected ApplicationEventPublisher eventPublisher;
    public void imports() {
        // 发布简单知识导入事件
        eventPublisher.publishEvent(new ImportedKnowledgeEvent(this, new Knowledge()));
        // 发布知识+文档导入事件
        eventPublisher.publishEvent(new ImportedKnowledgeEvent(this, new Knowledge(), new KWDocument()));
    }
}

@Service
public class KnowledgeRagflowService extends KnowledgeService {
    @EventListener
    public void importedKnowledge(KnowledgeService.ImportedKnowledgeEvent event) {
        if (event.getDocument() != null) {
            dealDocument(event.getKnowledge(), event.getDocument());
        } else {
            dealKnowledge(event.getKnowledge());
        }
    }
    private void dealDocument(Knowledge knowledge, Document document) {
        // 处理文档逻辑
    }
    private void dealKnowledge(Knowledge knowledge) {
        // 处理知识逻辑
    }
}

@EventListener(condition = "#event.document != null")
public void handleDocumentEvent(ImportedKnowledgeEvent event) {
    // 仅处理包含document的事件
}

@Async
@EventListener
public void asyncHandleEvent(ImportedKnowledgeEvent event) {
    // 异步处理耗时操作
}

@Configuration
@EnableAsync
public class AsyncConfig implements AsyncConfigurer {
    @Override
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(5);
        executor.setMaxPoolSize(10);
        executor.setQueueCapacity(25);
        executor.initialize();
        return executor;
    }
}

@Order(1)
@EventListener
public void firstListener(ImportedKnowledgeEvent event) {
    // 最先执行
}
@Order(2)
@EventListener
public void secondListener(ImportedKnowledgeEvent event) {
    // 其次执行
}

@TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
public void afterCommitEvent(ImportedKnowledgeEvent event) {
    // 事务提交后执行
}

@EventListener
public void handleEvent(ImportedKnowledgeEvent event) {
    try {
        // 业务处理
    } catch (Exception e) {
        // 1. 记录错误日志
        // 2. 发布错误处理事件
        // 3. 重试机制（如Spring Retry）
    }
}

@SpringBootTest
class KnowledgeEventTest {
    @Autowired
    private ApplicationEventPublisher eventPublisher;
    @MockBean
    private KnowledgeRagflowService ragflowService;
    @Test
    void shouldTriggerListenerWhenPublishEvent() {
        // 准备测试事件
        ImportedKnowledgeEvent event = new ImportedKnowledgeEvent(this, new Knowledge());
        // 发布事件
        eventPublisher.publishEvent(event);
        // 验证监听器调用
        verify(ragflowService, timeout(1000)).importedKnowledge(event);
    }
}

@EventListener
public void onApplicationReady(ContextRefreshedEvent event) {
    // 应用启动完成后初始化资源
}

@EventListener
public void auditLog(ImportedKnowledgeEvent event) {
    log.info("Knowledge imported: {}", event.getKnowledge().getId());
}

// 使用标记防止循环
public void imports() {
    if (!EventContext.isEventProcessing()) {
        eventPublisher.publishEvent(...);
    }
}