Which simple Java JPA ORM tool to use ?

Question

What Java ORM library implementing JPA that match following criteria would you recommend and why ?

• free & open source
• alive (at least bug fixes and a mailing list)
• with good documentation
• simple (simpler than hibernate)

I need to select a simple ORM tool that can be set up in minutes, without too much configuration and easy to understand, for setting simple CRUD DAOs. A query builder will be an interesting plus. Later I can have to move to Hibernate, that's why being JPA compliant is a must.

I have found some candidates on the web, but not so much feedback, so I will gladly take your advices on the topic.

----- EDIT ---------
I have been successfully testing ebean/avaje with a small test cases. Any one has a feedback on using these tools in production ?

Answer 1

If you only have a small data model to worry about, why not use JDBC or a wrapper around it (e.g. Spring JDBC) to handle the boilerplate? That plus an active record architecture (objects know how to save/update themselves) on your model classes isn't that difficult to understand or maintain, and you're leaving your options very open for another tool down the road if you decide you need full ORM later.

Answer 2

I'm currently using JPA/hibernate/hsqldb(test), mysql(deployment). Not very difficult to do especially if you use maven to handle dependencies. Failing that (and you don't want to use hibernate) - you could try OpenJPA.

Answer 3

I am late with my response, but I have a tool for you: https://sourceforge.net/apps/trac/jooq/wiki/Manual

Unfortunately, you won't have JPA-compliance there. But if you're used to jOOQ, you don't want to "go JPA" anymore :-)

Answer 4

Apache Cayenne is the unsung hero. Really sad no one is talking about it.

The killer feature of Apache Cayenne is the CayenneModeler which it is a GUI tool for database reverse engineering and generation, as well as a Velocity-based class generation engine.

Answer 5

I'm happy using MyBatis. In the past they called their approach "query mapping" opposed to "object mapping" since MyBatis does map (complex) SQL queries on results. This is a different concept than ORM.

Today they say this about their project:

The MyBatis data mapper framework makes it easier to use a relational database with object-oriented applications.

"Data mapper" seems to be a more general term.