Following code is used to create Hibernate HSQL connection.

Java Code:
<!DOCTYPE hibernate-configuration PUBLIC
  "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
  <session-factory>
     <!-- Database connection settings -->
        <property name="connection.driver_class">org.hsqldb.jdbcDriver</property>
        <property name="connection.url">jdbc:hsqldb:mem:testdb</property>
        <property name="connection.username">sa</property>
        <property name="connection.password"></property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">2</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.HSQLDialect</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup 
        <property name="hbm2ddl.auto">create</property>-->

        <mapping resource="Keyword.hbm.xml"/>
  </session-factory>
</hibernate-configuration>