Haber prueba con esto:
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="connection.driver_class">org.postgresql.Driv er</property>
<property name="connection.url">jdbc:postgresql://localhost:5432/gestAbogado</property>
<property name="connection.username">postgres</property>
<property name="connection.password">postgres</property>
<property name="dialect">org.hibernate.dialect.PostgreSQLDia lect
</property>
<mapping resource="com/gestAbogado/modelo/cliente.hbm.xml"/>
</session-factory>
</hibernate-configuration>
saludos!!