Hypersonic is the default database that comes as a 'working example' with Expresso.

 
<context name="default">
	<description>Hypersonic Database</description>
	<jdbc driver="org.hsqldb.jdbcDriver" 
		url="jdbc:hsqldb:%web-app%WEB-INF/db/default/default" 
		connectFormat="3" login="sa" 
		password="" 
		cache="y" 
		createTableIndicies="true" 
		limitationPosition="" 
		escapeHandler="com.jcorporate.expresso.core.db.DoubleQuoteEscapeHandler"/>
	<type-mapping>
		<java-type>LONGVARCHAR</java-type>
		<db-type>LONGVARCHAR</db-type>
	</type-mapping>
	<type-mapping>
		<java-type>BLOB</java-type>
		<db-type>BINARY</db-type>
	</type-mapping>
	<type-mapping>
 		<java-type>CLOB</java-type>
		<db-type>LONGVARCHAR</db-type>
	</type-mapping>
	<images>%context%/%expresso-dir%/images</images>
	<startJobHandler>y</startJobHandler>
	<showStackTrace>y</showStackTrace>
 	<mailDebug>n</mailDebug>
 </context>