public class BuyOrder {

  private Integer id;
  private String odaNumber;
  private String company;

  private Organization expediter1;
  private Organization expediter2;

  private List<BuyOrderItem> orderItems;
}

public class Organization {

  private Integer id;
  // XML tag -> Code
  private String sapCode;
  // XML tag -> Description
  private String companyName;

}

<?xml version="1.0" encoding="US-ASCII"?>
<xml-bindings xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm" package-name="it.mysigl.datamodel"
              xml-mapping-metadata-complete="true">

        <java-type name="BuyOrder">
            <xml-root-element name="Header"/>

            <java-attributes>
                <xml-element java-attribute="odaNumber" name="oda_number"/>
                <xml-element java-attribute="company" name="company"/>
               

                <xml-element java-attribute="orderItems" name="Item"/>
            </java-attributes>
        </java-type>
        <java-type name="BuyOrderItem">
            <java-attributes>
                <xml-element java-attribute="odaPos" name="oda_pos"/>
                <xml-element java-attribute="division"/>
            </java-attributes>
        </java-type>
        <java-type name="it.mysigl.datamodel.Organization">
            <java-attributes>
                <xml-element java-attribute="companyName" name="oda_pos"/>
                <xml-element java-attribute="sapCode" name="expediter1_code"/>
            </java-attributes>
        </java-type>
    </java-types>
</xml-bindings>

<?xml version="1.0" encoding="UTF-8"?>
<IM_ME_XML_Outbound>
	<Header>
		<oda_number>7211000000</oda_number>
		<company>NA1 </company>

		<expediter1_code>0000009375</expediter1_code>
		<expediter1_description>MYCOMPANY S.P.A.            </expediter1_description>
		<expediter2_code>0000644415</expediter2_code>
		<expediter2_description>NAMIBIA PTY                 </expediter2_description>
		
		<Item>
			<oda_pos>00010</oda_pos>
			<division>NA11</division>

		</Item>
		<Item>
			<oda_pos>00020</oda_pos>
			<division>NA12</division>

		</Item>
	</Header>
</IM_ME_XML_Outbound>