Java 在@Async调用中正确使用EntityManager

我试图使用Spring框架的

@Async

功能来执行简单的索引任务

我面临的问题是，我觉得异步函数中使用的

EntityManager

以某种方式从以前的调用中重用，因此我的数据不是最新的，有时使用旧数据

下面是我作为示例编写的代码。目标是在使用Spring的

ApplicationEventPublisher

发布事件后，更新产品数据并对其进行异步索引：

产品服务

@Service
class ProductService {

    private final EntityManager entityManager;

    private final ApplicationEventPublisher eventPublisher;

    @Autowired
    public ProductService(EntityManager entityManager, ApplicationEventPublisher eventPublisher) {
        this.entityManager = entityManager;
        this.eventPublisher = eventPublisher;
    }

    @Transactional
    public void patchProduct (String id, ProductDto productDto) {
        Product product = this.entityManager.find(Product.class, id);
        product.setLabel(productDto.getLabel());
        this.entityManager.flush();
        this.eventPublisher.publishEvent(new ProductEvent(product, ProductEvent.EVENT_TYPE.UPDATED));
    }
}

EventListener

@Component
public class ProductEventListener {

    private final AsyncProcesses asyncProcesses;

    @Autowired
    public ProductEventListener (
        AsyncProcesses asyncProcesses
    ) {
        this.asyncProcesses = asyncProcesses;
    }

    @EventListener
    public void indexProduct (ProductEvent productEvent) {
        this.asyncProcesses.indexProduct(productEvent.getProduct().getPok());
    }
}

异步进程

@Service
public class AsyncProcesses {

    private final SlowProcesses slowProcesses;

    @Autowired
    public AsyncProcesses(SlowProcesses slowProcesses) {
        this.slowProcesses = slowProcesses;
    }

    @Async
    public void indexProduct (String id) {
        this.slowProcesses.indexProduct(id);
    }
}

@Service
public class SlowProcesses {

    private EntityManager entityManager;

    private ProductSearchService productSearchService;

    @Autowired
    public SlowProcesses(EntityManager entityManager, NewProductSearchService newProductSearchService) {
        this.entityManager = entityManager;
        this.newProductSearchService = newProductSearchService;
    }

    @Transactional(readonly = true)
    public void indexProduct (String pok) {
        Product product = this.entityManager.find(Product.class, pok);
        // this.entityManager.refresh(product); -> If I uncomment this line, everything works as expected
        this.productSearchService.indexProduct(product);
    }
}

慢进程

@Service
public class AsyncProcesses {

    private final SlowProcesses slowProcesses;

    @Autowired
    public AsyncProcesses(SlowProcesses slowProcesses) {
        this.slowProcesses = slowProcesses;
    }

    @Async
    public void indexProduct (String id) {
        this.slowProcesses.indexProduct(id);
    }
}

@Service
public class SlowProcesses {

    private EntityManager entityManager;

    private ProductSearchService productSearchService;

    @Autowired
    public SlowProcesses(EntityManager entityManager, NewProductSearchService newProductSearchService) {
        this.entityManager = entityManager;
        this.newProductSearchService = newProductSearchService;
    }

    @Transactional(readonly = true)
    public void indexProduct (String pok) {
        Product product = this.entityManager.find(Product.class, pok);
        // this.entityManager.refresh(product); -> If I uncomment this line, everything works as expected
        this.productSearchService.indexProduct(product);
    }
}

正如您在SlowProcesses文件中看到的，如果我在entityManager中刷新产品对象，我将获得正确的最新数据。如果没有，我可能会从以前的调用中获取旧数据

在异步调用中使用EntityManager的正确方法是什么？我真的必须刷新所有对象才能使一切正常工作吗？我还做错什么了吗？

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感谢您通读

，因为EntityManager的实例并不像Jordie所指出的那样是线程安全的，所以您可以尝试以下方法：

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与其注入EntityManager，不如注入EntityManager工厂。然后从EntityManager工厂检索一个新的EntityManager实例，该实例仅在所讨论的方法期间使用。

EntityManager实例不是线程安全的。