Axis2: Avoid "Unexpected subelement" error when non-required property added to WSDL

Question

I have a .NET WCF service and a Java app that uses Axis2 to generate service stubs. When I add an optional property to a data contract in WCF and sort it at the end of the property list (which should be a backwards-compatible change) it causes Unexpected subelement errors in the Java app. The only way to fix it is to regenerate the stubs in Axis2 and redeploy the Java app -- not an acceptable approach in my case.

To be clear, I have not changed the order of the properties and the WSDL is valid. Here's an example of a type from the WSDL from before (when the Java app worked) and after (which causes the "Unexpected subelement" error):

<!-- BEFORE -->
<xs:complexType name="MyObject">
   <xs:sequence>
      <xs:element minOccurs="0" name="Name" nillable="true" type="xs:string"/>
   </xs:sequence>
</xs:complexType>

<!-- AFTER -->
<xs:complexType name="MyObject">
   <xs:sequence>
      <xs:element minOccurs="0" name="Name" nillable="true" type="xs:string"/>
      <xs:element minOccurs="0" name="MyNewProperty" nillable="true" type="xs:string"/>
   </xs:sequence>
</xs:complexType>

The AFTER version causes this error: org.apache.axis2.AxisFault: org.apache.axis2.databinding.ADBException: Unexpected subelement {http://mycompany.com/services/}MyNewProperty

Is there something we can do with Axis2 to prevent this from happening? If not, is there something different we should do in the WSDL or on the WCF side?

Answer 1

It appears that this is not a backwards-compatible change from the point of view of the XML Schema. If I ask XSV to validate a message

<MyObject>
    <Name>Primus Secundus</Name>
    <MyNewProperty>Addita notitia</MyNewProperty>
</MyObject> 

against your <!-- BEFORE --> schema, I get an error indicating that the MyNewProperty is invalid:

Invalid per cvc-complex-type.1.2.4: element {None}:MyNewProperty not allowed here (2) in element {None}:MyObject, expecting [$]:

I can't find anything in the XML Schema documentation (http://www.w3.org/TR/xmlschema-1/) or in either SOAP version (http://www.w3.org/TR/soap/) which indicates that extending a sequence with new elements for new properties should be allowed.

---

I used XSV at http://www.w3.org/2001/03/webdata/xsv, and uploaded the data in the following wrapper:

<?xml version="1.0"?>
<wrapper xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="#mySchema">
    <xs:schema id="mySchema" xmlns:xs="http://www.w3.org/2001/XMLSchema">
        <xs:element name="wrapper">
            <xs:complexType>
                <xs:sequence>
                    <xs:any/>
                    <xs:element name="MyObject" type="MyObject"/>
                </xs:sequence>
            </xs:complexType>
        </xs:element>
        <!-- BEFORE -->
        <xs:complexType name="MyObject">
            <xs:sequence>
                <xs:element minOccurs="0" name="Name" nillable="true" type="xs:string"/>
            </xs:sequence>
        </xs:complexType>
    </xs:schema>
    <MyObject>
        <Name>Primus Secundus</Name>
        <MyNewProperty>Addita notitia</MyNewProperty>
    </MyObject> 
</wrapper>