I am trying to run my batch job in parallel by utilizing java 8 parallel streams:
ForkJoinPool forkJoinPool = new ForkJoinPool(8);
forkJoinPool.execute(() -> tenants.parallelStream()
.forEach((tenant) -> getDataPerTenant(tenant)));
In getDataPerTenant(tenant), I am using jpa to access database and I am running a bunch of queries. The first problem I encountered was that the ContextClassLoader was null. I then tried to set the ContextClassLoader but followed this post: Parallel stream doesn't set Thread.contextClassLoader after tomcat upgrade and tried creating a ForkJoinPool.
However, threads maintained by ForkJoinPool throw an exception when creating an EntityManager:
No Persistence provider for EntityManager named TestService
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:85)
I believe this is because no Persistence Providers could be resolved.
Is there anyway to set the persistence provider for a thread? Just to clarify I have a persistence.xml and JPA works when threads are created by web application.
This problem only occurs when I try to spawn new threads that want to access JPA layer.
Any help will be greatly appreciated Thanks!
