JAXB: Unmarshalling does not always populate certain classes?

I have a JAXB class generation problem I was hoping to get some help with. Here's the part of the XML that is the source of my problem...

<xs:complexType name="IDType"> 
<xs:choice minOccurs="0" maxOccurs="2"> 
  <xs:element name="DriversLicense"    minOccurs="0" maxOccurs="1" type="an..35" /> 
    <xs:element name="SSN"        minOccurs="0" maxOccurs="1" type="an..35" /> 
    <xs:element name="CompanyID"       minOccurs="0" maxOccurs="1" type="an..35" /> 
  </xs:choice> 
</xs:complexType> 
<xs:simpleType name="an..35"> 
  <xs:restriction base="an"> 
    <xs:maxLength value="35" /> 
  </xs:restriction> 
</xs:simpleType> 

<xs:simpleType name="an"> 
   <xs:restriction base="xs:string"> 
     <xs:pattern value="[ !-~]*" /> 
   </xs:restriction> 
</xs:simpleType>

...now this will generate JAXBElement types due the the choice with a maxOccurs > 1 . I want to avoid those, so I did that by modifying the code to use a "Wrapper" element and move the maxOccurs up to a sequence tag as follows...

<xs:complexType name="IDType"> 
<xs:sequence maxOccurs="2"> 
  <xs:element name=Wrapper>
  <xs:complexType>
  <xs:choice> 
  <xs:element name="DriversLicense"    minOccurs="0" maxOccurs="1" type="an..35" /> 
    <xs:element name="SSN"        minOccurs="0" maxOccurs="1" type="an..35" /> 
    <xs:element name="CompanyID"       minOccurs="0" maxOccurs="1" type="an..35" /> 
  </xs:choice>
  </xs:complexType>
  </xs:element>
</xs:sequence> 
</xs:complexType>

<xs:simpleType name="an..35"> 
  <xs:restriction base="an"> 
    <xs:maxLength value="35" /> 
  </xs:restriction> 
</xs:simpleType> 

<xs:simpleType name="an"> 
   <xs:restriction base="xs:string"> 
     <xs:pattern value="[ !-~]*" /> 
   </xs:restriction> 
</xs:simpleType> 

For class generating, looks like it works great - the JAXB element is replaced wi开发者_Python百科th a list of wrappers as String (i.e. List<IDType.Wrapper<String> ) and compiles fine.

However, when I unmarshall the actual XML data into the generated classes the data in the wrapper class is not populated - yet JAXB does not throw an exception.

My question is: Do I need to change the schema a different way to make this work? Or is there something I can add/change/delete to the generated code or annotations?

Not a bad idea, but note the following: according to your schema, it is perfectly legal that your "Wrapper" element has no content. It contains a choice of optional items.

Secondly, you may not have schema validation on; then JAXB will not complain if your documents are broken. If you want to turn on schema validation, get an Unmarshaller and initialise like this:

 unmarshaller.setValidating(true);
 SchemaFactory sf = SchemaFactory.newInstance(
    javax.xml.XMLConstants.W3C_XML_SCHEMA_NS_URI);
 Schema schema = sf.newSchema(new File("my-schema.xsd"));
 unmarshaller.setSchema(schema);