Multiple persistence-unit tags in one persistence.xml

Question

I'm working now with a JPA 2.0 project (in Eclipse Indigo). In my persistence.xml file I need to specify two <persistence-unit> tags, because I have two different database to work with. Doing this, I get the following warning:

Multiple persistence units defined - only the first persistence unit will be recognized

Even more, if I create my entities and put it in my second <persistence-unit>, I get an error saying that my entity isn't declared in a persistence-unit:

Class "my.package.MyClass" is mapped, but is not included in any persistence unit

So, the question is: is possible to declare (and use them as expected) many <persistence-unit> tags in persistence.xml file? If yes, what do I need to do for getting the accurate behavior?

Thanks!

Answer 1

JPA does not limit number of persistence units defined in persistence.xml. This warning just tells about limitation of tool in Eclipse IDE. This is told for example here http://www.eclipse.org/webtools/dali/gettingstarted.php :

Currently Dali only supports one Persistence Unit and one Persistence XML file per project. Other configurations can exist in a JPA project, but the validation and defaults processing may not be correct when multiple persistence units are used.

I guess there is no known way to get this work in Eclipse IDE.

Answer 2

While this is JPA valid, you may also turn off the resulting (annoying) error notifications on a per-project basis by going into

Project Properties => JPA => Errors/Warnings

Activate Enable project specific settings and under Type, change the notification level for Class is mapped but is not in a persistence unit from Error to anything else you're comfortable with.

Update for Eclipse Luna:

The location and name of the setting has changed in Luna. The new location is:

Project Properties => JPA => Errors/Warnings

Check Enable project specific settings

Expand Project group

Change Multiple persistence units defined: to Ignore.