Hibernate - java.lang.OutOfMemoryError: Java heap space

Question

I get this exception:

Exception in thread \"AWT-EventQueue-0\" java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOf(Arrays.java:2882)
    a         


        

Answer 1

A tip I picked up from many years of pain with this sort of thing: the answer is usually carefully hidden somewhere in first 10 lines of the stack trace. Always read the stack trace several times, and if that doesn't give enough help, read the source code of the methods where the failure happens.

In this case the problem comes from somewhere in Hibernate's pretty printer. This is a logging feature, so the problem is that Hibernate is trying to log some enormous string. Notice how it fails while trying to increase the size of a StringBuilder.

Why is it trying to log an enormous string? I can't say from the information you've given, but I'm guessing you have something very big in your Organization entity (maybe a BLOB?) and Hibernate is trying to log the objects that the query has pulled out of the database. It may also be a mistake in the mapping, whereby eager fetching pulls in many dependent objects - e.g. a child collection that loads the entire table due to a wrong foreign-key definition.

If it's a mistake in the mapping, fixing the mapping will solve the problem. Otherwise, your best bet is probably to turn off this particular logging feature. There's an existing question on a very similar problem, with some useful suggestions in the answers.