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

The problem is not with parallel stream .In spring transaction is created using AOP.
When your processCollection method is executed spring create a proxy object of this and transaction is started. Calling anyother method in same class ,spring will not run that method in New transaction even if you specified @Transaction . To get it run move that method process() to new service and then execute your problem.your program will work fine.

Answer 2

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.