There are so many JavaPersistence frameworks, these days.  It's hard to choose between them.  But when you're choosing, don't neglect lowly JDBC as an alternative.

JDBC has some real advantages, and in my experience, is often all you need.
 * It's simple.
 * The SQL queries are just that, and can be tuned by any competent DBA.  (versus EJBQL used by entity beans)
 * Performance is good.

JDBC gets a bad rap for difficulty because so many people take such an ad-hoc approach.  To mitigate the difficulty, and the fragile, error-prone approaches I've seen far too often, I've released a JDBC implementation under a BSD-like license: [[http://idiacomputing.com/idia-1.0.src.zip]]. ('''The zip is complete, now.  I'd forgotten to include the tests that access the database.''')

This package provides a couple of abstract base classes (one for reading and one for writing) that you can extend for your needs.  These base classes take care of the common actions, leaving you to implement methods to furnish the database connection (so that you can take advantage of pooling or whatever container your code uses), the SQL, and to bind variables to the SQL.  In the case of reads, you provide a method for processing a single row of the resultset.  No matter what happens, all of the JDBC resources will get closed.  There are hooks for logging and for reading single rows, also.