...
<middlegen
    appname="${name}"
    prefsdir="${src.dir}"
    gui="${gui}"
    databaseurl="${database.url}"
    initialContextFactory="${java.naming.factory.initial}"
    providerURL="${java.naming.provider.url}"
    datasourceJNDIName="${datasource.jndi.name}"
    driver="${database.driver}"
    username="${database.userid}"
    password="${database.password}"
    schema="${database.schema}"
    catalog="${database.catalog}"
  >

     <!-- Plugins -->
     <hibernate
        destination="${build.gen-src.dir}"
        package="${name}.hibernate"
        javaTypeMapper="middlegen.plugins.hibernate.HibernateJavaTypeMapper"
     />

   </middlegen>
   <mkdir dir="${build.classes.dir}"/>
</target>

<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >

<hibernate-mapping>
<!--

Created by Middlegen Hibernate plugin
http://boss.bekk.no/boss/middlegen/
http://hibernate.sourceforge.net/

-->
<class
  name="airline.hibernate.Flight"
  table="flights"
schema="fdgdf"    <----
  proxy="airline.hibernate.Flight"
>

<hibernate
      destination="${build.gen-src.dir}"
      package="${name}.hibernate"
      databaseSchema="myschema"
/>