Question

我正在从事Spring Boot应用程序的事件驱动设计。

代码包含以下文件：

春季启动：ApplicationEvent文件，即MyBusinessEvent。{java

@Data
@AllArgsConstructor
public class MyBusinessEvent {

   private String data;

}

事件发布者文件：MyBusinessService.java

@Slf4j
@Service
public class MyBusinessService {

    private final ApplicationEventPublisher applicationEventPublisher;

    @Autowired
    public MyBusinessService(
            ApplicationEventPublisher applicationEventPublisher) {

        this.applicationEventPublisher = applicationEventPublisher;
    }

    @Override
    public void save() {
        String data = "Testing event data";
        MyBusinessEvent event = new MyBusinessEvent(data);
        applicationEventPublisher.publishEvent(event);
    }
}

EventListener：MyBusinessEventListener.java

@Slf4j
@Component
public class MyBusinessEventListener {

    @EventListener
    public void handleEvent(MyBusinessEvent myBusinessEvent) {
        log.info("[MyBusinessEventListener] New event received with following data: {}", myBusinessEvent);
    }
}

重点是，当侦听器文件包含@EventListener时，应用程序将按预期运行，但是当我执行@TransactionEventListener时。例如：

TransactionalEventListener：MyBusinessEventListener.java

@Slf4j
@Component
public class MyBusinessEventListener {

    @TransactionalEventListener
    public void handleEvent(MyBusinessEvent myBusinessEvent) {
        log.info("[MyBusinessEventListener] New event received with following data: {}", myBusinessEvent);
    }
}

对于@TransactionalEventListener，它根本不起作用。

应用程序没有遇到任何异常（即使在运行时也没有异常），但是没有按预期的记录。

是否缺少任何配置？

Answer 1

向@Transactional添加MyBusinessService.save注释应该可以解决此问题。

根据Java文档，@TransactionalEventListener在@Transactional范围内工作。

这是文档所说的

If the event is not published within the boundaries of a managed transaction, the
 * event is discarded unless the {@link #fallbackExecution} flag is explicitly set.

如果您不想在事务边界中使用服务方法，请使用@TransactionalEventListener(fallbackExecution = true)

编辑：解决上述问题的方法有三种。

i。将class标记为@Transactional视为可交易

@Transactional
@Service
public class MyBusinessService {

    private final ApplicationEventPublisher applicationEventPublisher;

    @Autowired
    public MyBusinessService(
            ApplicationEventPublisher applicationEventPublisher) {

        this.applicationEventPublisher = applicationEventPublisher;
    }

    @Override
    public void save() {
        String data = "Testing event data";
        MyBusinessEvent event = new MyBusinessEvent(data);
        applicationEventPublisher.publishEvent(event);
    }
 }

ii。将特定的服务方法设置为@Transactional

@Override
@Transactional
public void save() {
    String data = "Testing event data";
    MyBusinessEvent event = new MyBusinessEvent(data);
    applicationEventPublisher.publishEvent(event);
}

iii。如果您不希望在事务边界中使用服务方法，请使用

@Slf4j
@Component
public class MyBusinessEventListener {

    @TransactionalEventListener(fallbackExecution = true)
    public void handleEvent(MyBusinessEvent myBusinessEvent) {
        log.info("[MyBusinessEventListener] New event received with following data: {}", myBusinessEvent);
    }
}

Answer 2

您的ApplicationEventPublisher类应如下所示：@ Slf4j @Service public

class MyBusinessService {

    private final ApplicationEventPublisher applicationEventPublisher;

    @Autowired
    public MyBusinessService(
            ApplicationEventPublisher applicationEventPublisher) {

        this.applicationEventPublisher = applicationEventPublisher;
    }

    @Override
    @Transactional
    public void save() {
        String data = "Testing event data";
        MyBusinessEvent event = new MyBusinessEvent(data);
        applicationEventPublisher.publishEvent(event);
    }
 }

但是请注意，这种功能的可交易性特别是指数据库的可交易性。

如果您希望在事件监听器发生异常的情况下，如果事件监听器消耗的消息再次可用，则此功能不受支持，在这种情况下，您应该考虑像RabbitMQ这样的消息代理，它支持事务性消息传递

如果您尚未在应用程序中使用Spring Cloud，我建议您使用Spring Cloud Stream，它可以帮助您创建事件驱动的应用程序。

Spring云流的好处在于，它为您提供了一些与所使用的消息代理无关的抽象概念。

您可以在所有支持的活页夹之间切换，而无需更改应用程序中的任何内容

@TransactionalEventListener不起作用，因为@EventListener就像在同一上下文中的超级按钮一样

2 个答案: