Java .parallelStream() with spring annotated methods

Question

I try using the parallelStream() in DAO with Spring @Transactional annotations and get so problem:

@Transactional
public void processCo         


        

Answer 1

Well, I have a guess consists of several guesses:

• You have session management policy as session-per-thread;
• Object you wrote in example is in fact some entity that uses lazy loading;
• processOne() method uses entity properties that are loaded lazily;
• Because of first point, threads, started for parallelStream() has no session available (probably in ThreadLocal, don't remember how technically sessions are bound to threads);

That altogether causing the problem you have. The behavior looks quite strange to me, so I suggest to do the following:

• Remove all lazy loading and try parallelStream() again;
• If that succeeds, you'll have to load the entities completely before performing parallelStream().

Alternative way to go: detaching all list elements from session before doing parallelStream().

Although as Marko wrote in comments, Session is not thread-safe, so that means you have to get rid of Session usage either by removing lazy loading, or by detaching all entities from session.