Exemplo de arquivo persistence.xml para projetos utilizando o JPA com HSQLDB em memória.

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="exemploPU" transaction-type="RESOURCE_LOCAL">
	
	
		<properties>
			<property name="javax.persistence.jdbc.url" value="jdbc:hsqldb:mem:exemplo;shutdown=true;hsqldb.write_delay=false"/>
			<property name="javax.persistence.jdbc.user" value="SA"/>
			<property name="javax.persistence.jdbc.password" value=""/>
			<property name="javax.persistence.jdbc.driver" value="org.hsqldb.jdbc.JDBCDriver"/>
			
			<!-- validate | update | create | create-drop -->
			<property name="hibernate.hbm2ddl.auto" value="update"/>
			<property name="hibernate.show_sql" value="true"/>
			<property name="hibernate.format_sql" value="true"/>
			<property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
			
		</properties>
		
	
	</persistence-unit>
	
	
</persistence>