When I add @Async, entityManager.flush() will raise an exception

问题

I'm using Spring framework.

The structure of my project is Controller ➡️ Service ➡️ Logic.

I added @Transactional in Logic class. I am using EntityManager to do DB operations. After every db operation(select, update...), I am calling entityManager.flush() method. Everything is fine.

But in order to improve performance, I added @Async in Service class. Then an exception is raised when I am calling entityManager.flush().

javax.persistence.TransactionRequiredException: no transaction is in progress
    at org.hibernate.internal.SessionImpl.checkTransactionNeeded(SessionImpl.java:3505)
    at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1427)
    at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1423)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:350)
    at com.sun.proxy.$Proxy150.flush(Unknown Source)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:305)
    at com.sun.proxy.$Proxy150.flush(Unknown Source)

I debugged the source and found that EntityManager is bound to thread by using ThreadLocal, but when I added @Async, there will be a new thread, this new thread will create a new EntityManager, that is OK. But when I call entityManager.flush(), it will check Transaction and call JdbcResourceLocalTransactionCoordinatorImpl.isJoined() method,physicalTransactionDelegate is null, so the exception will be raised.

physicalTransactionDelegate is initialized in main thread.

What should I do if I want to execute entityManager.flush()? Or is my understanding about the source wrong?

Controller.java

@GetMapping(value = "/getTest", produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
    public ResponseDto execute(@Valid final RequestDto requestDto) {
        List<CompletableFuture<Dto>> completableFutures = new ArrayList<>();
        for (ItemRequestDto item : requestDto.getItemRequestDtoList()) {
            completableFutures.add(service.execute(item));
        }
    }

Service.java

@Async("taskExecutor")
    public CompletableFuture<InventoryInfoListDto> execute(final ItemRequestDto item) {
        return CompletableFuture.completedFuture(logic.execute(item));
    }

Logic.java

@Transactional(rollbackFor = Throwable.class, timeout = 60)
public ResponseDto execute(final ItemRequestDto item) {
    // process...
}

I created an issue in github. https://github.com/spring-projects/spring-framework/issues/23325

回答1:

I found the solution. Just add entityManager.joinTransaction();.

回答2:

I think this is a bug.

• With No @Async
  • When request comes, TransactionSynchronizationManager.bindResource((Object key, Object value) will be called, and a new EntityManager will be bound to current thread.
  • Then, EntityManagerFactoryUtils.doGetTransactionalEntityManager(EntityManagerFactory emf, @Nullable Map<?, ?> properties, boolean synchronizedWithTransaction) is called to get the bound EntityManager. Inside this method, it will call EntityManager.joinTransaction(). This method will call JdbcResourceLocalTransactionCoordinatorImpl.getTransactionDriverControl() to initialize TransactionDriverControlImpl physicalTransactionDelegate.
  • When we call EntityManager.flush(). JdbcResourceLocalTransactionCoordinatorImpl.isJoined()will be called to check.
• With @Async
  • When request comes, TransactionSynchronizationManager.bindResource((Object key, Object value) will be called, and a new EntityManager will be bound to current thread.
  • If there is a @Async, a new thread will be created.
  • Then, EntityManagerFactoryUtils.doGetTransactionalEntityManager(EntityManagerFactory emf, @Nullable Map<?, ?> properties, boolean synchronizedWithTransaction) is called to get the bound EntityManager. But in this new thread, there is no bound EntityManager, so a new one will be created, but EntityManager.joinTransaction() will not be called. So TransactionDriverControlImpl physicalTransactionDelegate will not be initialized.
  • When we call EntityManager.flush(). Since TransactionDriverControlImpl physicalTransactionDelegate is null, an exception will be raised.

Why EntityManager.joinTransaction() is not called when a new EntityManager is created in a new thread?

来源：https://stackoverflow.com/questions/57129912/when-i-add-async-entitymanager-flush-will-raise-an-exception