I have my file hibernate.sar with the following structure:

META-INF/jboss-service.xml
mappings/Usuario.hbm.xml
co/edu/escuelaing/Usuario.class

Jboss-service.xml is:

<server> 
<mbean code="net.sf.hibernate.jmx.HibernateService" 
name="jboss.jca:service=HibernateFactory, 
name=HibernateFactory"> 
<depends>jboss.jca:service=RARDeployer</depends> 
<depends>jboss.jca:service=LocalTxCM,name=SigmaDS</depends> 
<!-- Make it deploy ONLY after DataSource had been started --> 
<attribute name="MapResources">/mappings/Usuario.hbm.xml</attribute> 
<attribute 
name="JndiName">java:/hibernate/HibernateFactory</attribute> 
<attribute name="Datasource">java:/SigmaDS</attribute> 
<attribute 
name="Dialect">net.sf.hibernate.dialect.PostgreSQLDialect</attribute> 
<attribute 
name="TransactionStrategy">net.sf.hibernate.transaction.JTATransactionF
actory</attribute> 
<attribute 
name="TransactionManagerLookupStrategy">net.sf.hibernate.transaction.JB
ossTransactionManagerLookup</attribute> 
<attribute name="UseOuterJoin">false</attribute> 
<attribute name="ShowSql">false</attribute> 
<attribute name="UserTransactionName">UserTransaction</attribute> 
</mbean> 
</server>

but when I run Jboss server, appears to me this: 

17:43:13,576 INFO [Configuration] Mapping resource: 
mappings/Usuario.hbm.xml 
17:43:13,597INFO [HibernateServiceMBean] Could not build 
SessionFactory using 
the MBean classpath - will try again using client classpath: Resource: 
mappings/Usuario.hbm.xml not found 

I do not know, why?