File APIs for Java Developers
Manipulate DOC, XLS, PPT, PDF and many others from your application.
The moose likes Tomcat and the fly likes jpa, datasource and tomcat Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login

Win a copy of Groovy Fundamentals video training course this week in the Groovy forum!
JavaRanch » Java Forums » Products » Tomcat
Bookmark "jpa, datasource and tomcat" Watch "jpa, datasource and tomcat" New topic

jpa, datasource and tomcat

nimo frey
Ranch Hand

Joined: Jun 28, 2008
Posts: 580
I use JPA(Hibernate) and have a persistence.xml and a context.xml bound to my database - all works well.

However, in the documentation I found that I have also declare the resource-ref in web.xml:

But I have not declare it, and it s working. So my question:

Do I have to declare the resource-ref, when having a persistence.xml already?
Tim Holloway
Saloon Keeper

Joined: Jun 25, 2001
Posts: 16737

The resource-ref connects your webapp to the Tomcat connection pooler. It establishes the JNDI name of the datasource object (java:/comp/env/jdbc/mt\yDataSource).

However, if you use a brute-force JPA implementation, it will create its own connection manager within the webapp, so this object will not be referenced.

That's not entirely a good idea, since it's often desirable to manage resources at the server level, but there's nothing otherwise wrong with it.

Myself, I'm using Spring to manage JPA and I have Spring configured to get the persistence parameters from the JNDI definition, but it's a bit more complicated that way. On the other hand, because I'm using the external pool, I can switch from test to production databases without changing persistence.xml, web.xml, recompiling any classes or rebuilding the WAR. I manage everything from the external Tomcat definitions for the test/production server.

Customer surveys are for companies who didn't pay proper attention to begin with.
nimo frey
Ranch Hand

Joined: Jun 28, 2008
Posts: 580

so is it better to provide additionally this information in my web.xml?:

The problem is, when I provide the above information, then I get this error:

I use mySQL and have definitly the lib "mysql-connector-java" in the tomcat-lib-folder (not in the applications web-inf/lib).

When I do NOT provide the resource-ref-information, then I get NO errors and all works.

Do you know, what is wrong?

(Maybe the DBCP of tomcat and the use of Hibernate JPA? I guess, Hibernate has its own (better?) connection pool?)
I agree. Here's the link:
subject: jpa, datasource and tomcat