java-tutorials/libraries-data-2/src/test/resources/user_jmapper2.xml

<jmapper>
  <class name="com.baeldung.jmapper.relational.User">
    <attribute name="id">
      <value name="id"/>
      <classes>
        <class name="com.baeldung.jmapper.relational.UserDto1"/>
        <class name="com.baeldung.jmapper.relational.UserDto2"/>
      </classes>
    </attribute>
    <attribute name="email">
      <attributes>
        <attribute name="username"/>
        <attribute name="email"/>
      </attributes>
      <classes>
        <class name="com.baeldung.jmapper.relational.UserDto1"/>
        <class name="com.baeldung.jmapper.relational.UserDto2"/>
      </classes>      
    </attribute>
  </class>
</jmapper>