Stuff that’s unfortunately not concentrated into a convenient ready-to-use example in the Apache OpenJPA docs. But that’s what this blog is all about!
When using the reverse engineering, schema, and other tools directly from a shell script (not Ant or Maven), the default place to get datasource definitions and related options is in META-INF/persistence.xml. This file is mandatory even in cases where you don’t actually connect to the database, such as generating Java source from an XML schema (reverse generation).
Because the tools are using a validating parser, a schema name is REQUIRED. Example, supplying the JPA schema via the xmlns attribute:
<?xml version="1.0"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">
<persistence-unit name="openjpa">
<provider>org.apache.openjpa.persistence.PersistenceProviderImpl</provider>
<properties>
<property name="openjpa.ConnectionURL" value="jdbc:hsqldb:tutorial_database"/>
<property name="openjpa.ConnectionDriverName" value="org.hsqldb.jdbcDriver"/>
<property name="openjpa.ConnectionUserName" value="sa"/>
<property name="openjpa.ConnectionPassword" value=""/>
<property name="openjpa.Log" value="DefaultLevel=WARN, Tool=INFO"/>
<property name="openjpa.jdbc.DBDictionary" value="StoreCharsAsNumbers=false"/>
</properties>
</persistence-unit>
</persistence>
CAUTION: You should delete the orm.xml file when re-running these tools. Otherwise they will use the old copy, which may not be in sync with your current efforts.
