OpenJPA > Is it possible to define persistence xml file somewhere else than META-INF with name persistence.xml - openjpa

Question

I am a new OpenJPA 2.2.2 user. I noticed that the database configuration has to be defined in META-INF/persistence.xml. This sounds to be too inflexible. Moreover, I found from the OpenJPA 2.2.2 documentation:
The OpenJPA runtime includes a comprehensive system of configuration defaults and overrides:
OpenJPA first looks for an optional openjpa.xml resource. OpenJPA searches for this resource in each top-level directory of your CLASSPATH. OpenJPA will also find the resource if you place it within a META-INF directory in any top-level directory of the CLASSPATH. The openjpa.xml resource contains property settings in JPA's XML format.
You can customize the name or location of the above resource by specifying the correct resource path in the openjpa.properties System property.
On base the introduction above, it seems that the database configuration file name is only possible to be persistence.xml. Moreover, I tried to place it in the top-level directory of my CLASSPATH, i.e., not inside the META-INF directory, it didn't work at all! Is there is any way to define this database persistence xml more flexibly, say in somewhere else than META-INF and with other name than persistence.xml?

Answer 1

First, there is no replacement for persistence.xml (p.xml for short). This is needed no matter what. Furthermore, the location of this file is clearly defined in the JPA specification (e.g. see "8.2 Persistence Unit Packaging" in JPA 2.0 spec). You MUST follow those rules on packaging. OpenJPA first and foremost follows the rules of the spec in regards to this file and its settings. No JPA provider is going to ignore the rules w.r.t p.xml file.
The section of text you copy/pasted is from here in the OpenJPA documentation:
http://openjpa.apache.org/builds/2.2.2/apache-openjpa/docs/manual#ref_guide_conf_specify
As you can see, this section describes an optional file named openjpa.xml. This file does not replace a p.xml file! It adds to it. And as the documentation states, it is simply used to add properties. That is, you can not define your persistence unit here, the only thing you can define are properties (i.e. ). If you define a persistence unit here, it will not be used. As an example, lets look at this openjpa.xml file:
<?xml version="1.0"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
version="1.0">
<persistence-unit name="">
<properties>
<property name="openjpa.jdbc.Schema" value="MySchema" />
<property name="openjpa.jdbc.DBDictionary" value="db2" />
</properties>
</persistence-unit>
This file defines two properties. Notice that the persistence-unit name is blank. That is intentional because, as I mentioned above, we can't define a persistence unit in this file. Finally, you can place this file in the META-INF on your classpath, as mentioned in the documentation. If you put this at the same spot as your p.xml file it will be found. As an example, in my JSE JUnit test, I place it on my hard drive in the directory e:/openjpaConfig/META-INF/openjpa.xml. I then put a classpath entry in my JUnit test to point to the directory e:/openjpaConfig. The classpath could point to a jar which contains this file in its META-INF directory. In a Java EE environment, you could place the file in a .jar file and place the .jar file in the lib directory of an ear.