[hibernate-issues] [Hibernate-JIRA] Created: (HHH-2627) Generated properties leak prepared statements in Hibernate 3.2.3 and higher.

[Michael Werle (JIRA)]

Generated properties leak prepared statements in Hibernate 3.2.3 and higher.
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                 Key: HHH-2627
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2627
             Project: Hibernate3
          Issue Type: Bug
          Components: core
    Affects Versions: 3.2.4.sp1, 3.2.4, 3.2.3
         Environment: Hibernate 3.2.2-4sp1, Oracle 10g (Oracle9Dialect)
            Reporter: Michael Werle
         Attachments: generated-lazy-statement-leak.patch

The fix for HHH-2393, in combination with a change to AbstractBatcher 11333 to the Hibernate 3.2 branch (comment is "sybase testsuite"), created a PreparedStatement leak for generated properties.

The reason is that, in revision 11333, org.hibernate.jdbc.AbstractBatcher#closeQueryStatement() was changed to check for the existence of the prepared statement in the statementsToClose collection instead of closing it unconditionally.  The fix for HHH-2393 (revision 11117 in the Hibernate 3.2 branch) modified org.hibernate.persister.entity.AbstractEntityPersister#processGeneratedProperties() to make it use org.hibernate.jdbc.AbstractBatcher#closeQueryStatement() instead of org.hibernate.jdbc.AbstractBatcher#closeStatement(), which closes the statement without checking the statementsToClose collection.  This is a problem because the statement in AbstractEntityPersister#processGeneratedProperties() is created with AbstractBatcher#prepareSelectStatement(), which does not add the statement to the statementsToClose collection.

The attached patch to org.hibernate.persister.entity.AbstractEntityPersister changes processGeneratedProperties() back to using AbstractBatcher#closeStatement() and obtains the result set through ResultSet#executeQuery() instead of using the batcher.  This fixes the prepared statement leak and matches other usages of AbstractBatcher#prepareSelectStatement(), which also avoid using the batcher for their result sets.  It also makes the same change in AbstractEntityPersister#initializeLazyPropertiesFromDatastore() becuase it has exactly the same problem.

No existing test cases are broken by the attached patch.  I investigated ways to write a test case to explicitly verify that the result sets and statements were all being closed.  However, because the counts in AbstractBatcher are private, and I do not know of a generic way to obtain counts through the JDBC API, I could not figure out a good way to do so without using reflection to access the private fields, which none of the existing test cases seem to do.

The bug was discovered when running my web app against Oracle, which runs out of cursors when connections are leaked -- not exactly a practical way to write a test case, but sufficient to prove that the bug exists and is fixed by the patch.

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