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I am a newbie to Hibernate.

I am considering Hibernate for an application that uses a database that is used by a number of other applications. These applications can insert and update rows in the database.

Can I use Hibernate in this situation without making changes to the other applications.

(My concern is in how the special Hibernate tables and indexes will be updated if the other programs don't use Hibernate.)

A variant on this question: if i have a legacy database I want to use with Hibernate are there tools that can make the db Hibernate readable.

Any responses or pointers to areas of the documentation that I might have missed would be much appreciated.

Sure you can. Considerations are the same regardless of the technique being used to access the database concurrently from multiple applications. Note: Hibernate does not require special tables or indexes to work correctly.

Middlegen is currently the recommended tool (Hibernate 2.x) to reverse engineer the database. See Wiki and Middlegen pages. Hibernate 3.x toolset will include database reverse engineering tools - it is being actively worked on at the moment.

A couple of notes from my experience with this:

1) Don't use the Increment generator. It only updates its counter once per SessionFactory.

2) Be careful about how you configure an L2 cache. I have a web application with multiple frames that load the same information on different HttpRequests. As a result I get big benefits from L2 caching. There are several tables, updated often using VB apps that I read from often but rarely write to. On these tables I use timeToLiveSeconds=30. This is long enough for each of the frames to load without having to hit the database repeatedly but short enough that changes made by other applications are available almost immediately. Of course, this strategy should not be used for financial or safety-critical data.