Automatic Table Generation in the roster Application

At deployment time, the GlassFish Server will automatically drop and create the database tables used by roster. This is done by setting the eclipselink.ddl-generation property to drop-and-create-tables in 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="em" transaction-type="JTA">
    <jta-data-source>jdbc/__default</jta-data-source>
    <properties>
      <property name="eclipselink.ddl-generation" 
                value="drop-and-create-tables"/>
    </properties>
  </persistence-unit>
</persistence>

This feature is specific to the Java Persistence API provider used by the GlassFish Server and is nonportable across Java EE servers. Automatic table creation is useful for development purposes, however, and the eclipselink.ddl-generation property may be removed from persistence.xml when preparing the application for production use or when deploying to other Java EE servers.