Propriedades da JPA

DataSource
referencia a um datasource:

<jta-data-source>java:comp/env/jdbc/simenet</jta-data-source> 

referencia a um datasource no tomcat (fora da JTA): Com HIBERNATE

<non-jta-data-source>java:comp/env/jdbc/simenet</non-jta-data-source> 

<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="default">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <properties>
            <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
            <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
            <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
            <property name="hibernate.connection.username" value="sa"/>
            <property name="hibernate.connection.password" value=""/>
            <property name="hibernate.connection.url" value="jdbc:hsqldb:."/>
            <property name="hibernate.max_fetch_depth" value="3"/>
        </properties>
    </persistence-unit>
</persistence>

Com TOPLINK

<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 persistence_1_0.xsd" version="1.0">
        <persistence-unit name="default">
                <provider>oracle.toplink.essentials.PersistenceProvider</provider>
                <exclude-unlisted-classes>false</exclude-unlisted-classes>
                <properties>
                        <property name="toplink.ddl-generation" value="drop-and-create-tables" />
                        <property name="toplink.logging.level" value="FINE" />
                        <property name="toplink.jdbc.url" value="jdbc:mysql://localhost/myDB" />
                        <property name="toplink.jdbc.driver" value="com.mysql.jdbc.Driver" />
                        <property name="toplink.jdbc.user" value="root" />
                        <property name="toplink.jdbc.password" value="" />
                </properties>
        </persistence-unit>
</persistence>

Configuração do TopLink para funcionamento com datasource no tomcat:

import oracle.toplink.essentials.jndi.JNDIConnector; import oracle.toplink.essentials.sessions.Session; import oracle.toplink.essentials.tools.sessionconfiguration.SessionCustomizer; public class ToplinkSessionCustomizer implements SessionCustomizer {   public void customize(Session session) throws Exception {     JNDIConnector connector = (JNDIConnector) session.getLogin()         .getConnector();     connector.setLookupType(JNDIConnector.STRING_LOOKUP);   } }

linha a ser acrescientada nas properties:

<property name="toplink.session.customizer" value="pacote.ToplinkSessionCustomizer"/>
veja link: http://forums.oracle.com/forums/thread.jspa?messageID=1899677