DDL generation and general persistence.xml settings (OpenJPA)

Question

Summary

I'm trying to run a Java web application JPA 2.0 example. The example application was written to run in Glassfish, using EclipseLink as JPA provider. I would like to convert it to run in TomEE with OpenJPA as the JPA provider, but I can't any detailed tutorials for getting up and running with OpenJPA.

Problem

I'm having trouble converting persistence.xml to work with OpenJPA instead of EclipseLink. More specifically, the given persistence.xml doesn't specify:

• Entity classes. Are these necessary?
• The desired JPA provider. Will the container default to something?
• The JDBC driver. How do I specify an "in-memory" DB (just for initial testing purposes)?

Also:

• How are the DDL generation properties expressed in OpenJPA? I wasn't able to find them the OpenJPA User Guide.

Details

Below is the EclipseLink persistence.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
    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_2_0.xsd">
    <persistence-unit name="order" transaction-type="JTA">
        <jta-data-source>jdbc/__default</jta-data-source>
        <properties>
            <property name="eclipselink.ddl-generation" value="drop-and-create-tables" />
            <property name="eclipselink.ddl-generation.output-mode"
                value="both" />
        </properties>
    </persistence-unit>
</persistence>

I have the following Entity classes:

• order.entity.LineItem
• order.entity.LineItemKey
• order.entity.Order
• order.entity.Part
• order.entity.PartKey
• order.entity.Vendor
• order.entity.VendorPart

Question

• Does anyone know what the equivalent persistence.xml would look like for OpenJPA?
• Alternatively, if anyone could point me to an OpenJPA tutorial that covers these issues that would be just as good

Answer 1

If you add the openjpa.jdbc.SynchronizeMappings property as shown below OpenJPA will auto-create all your tables, all your primary keys and all foreign keys exactly to match your objects

<property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)"/>

Alternatively, you can use EclipseLink in TomEE by just adding the EclipseLink jars to <CATALINA_HOME>/lib/

refer here for Common PersistenceProvider properties

Answer 2

Foreign key constraints

The next line does not create foreign keys:

<property name="openjpa.jdbc.SynchronizeMappings" 
          value="buildSchema(ForeignKeys=true)"/>

Only creates schema and deletes content of a database.

But if you want create foreign keys, use the following lines:

<property name="openjpa.jdbc.SynchronizeMappings" 
          value="buildSchema(foreignKeys=true,schemaAction='dropDB,add')"/>
<property name="openjpa.jdbc.SchemaFactory" 
          value="native(foreignKeys=true)" />
<property name="openjpa.jdbc.MappingDefaults" 
          value="ForeignKeyDeleteAction=restrict, JoinForeignKeyDeleteAction=restrict"/>

See generated SQL

In another way, if you want to see the SQL output:

<property name="openjpa.Log" 
          value="DefaultLevel=TRACE,SQL=TRACE" />

_{NOTE: In order to see the generated output in the TomEE console, you need to change the log level in the file loggin.properties with openjpa.level = FINEST}

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See more in http://openjpa.apache.org/faq.html