Hi,
I am trying to use jaxb 2.2.6-ri to marshall/unmarshall xml documents
using the SDMX (Statistical Data Metadata Exchange), and I am
encountering
an InstantiationException related to use of abstract classes and
derivation by restriction.
The complete schema is rather complex
(you can download it at the following location
http://sdmx.org/wp-content/uploads/2012/11/SDMX_2-1_SECTION_3A_SDMX_ML.
zip),
but I was able to track down the problem I am encountering tp the
following small
sample.
Here is the schema (sdmx_reduced.xsd) :
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema version="1.0" xmlns:xs="
http://www.w3.org/2001/XMLSchema">
<xs:element name="Structure" type="StructureType"/>
<xs:complexType name="StructureHeaderType">
<xs:complexContent>
<xs:restriction base="BaseHeaderType">
<xs:sequence>
<xs:element name="ID" type="xs:string"/>
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="StructureType">
<xs:complexContent>
<xs:restriction base="MessageType">
<xs:sequence>
<xs:element name="Header" type="StructureHeaderType"/>
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="MessageType" abstract="true">
<xs:sequence>
<xs:element name="Header" type="BaseHeaderType"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="BaseHeaderType" abstract="true">
<xs:sequence>
<xs:element name="ID" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:schema>
In this schema, I have used the same names as in the original
SDMX schema, but have ommited namespaces. I generated Java classes
using :
xjc.sh sdmx_reduced.xsd
I am using the following code java code to unmarshall the xml document
JAXBContext jAXBContext =
JAXBContext.newInstance("generated");
Unmarshaller unmarshaller = jAXBContext.createUnmarshaller();
StructureType structure=
(StructureType)unmarshaller.unmarshal(
new File("/tmp/structure.xml"));
This code triggers an InstantiationException.
Here is the content of the /tmp/structure.xml file :
<?xml version="1.0" encoding="UTF-8"?>
<Structure>
<Header>
<ID>Sample_DSD1_With_No_Group</ID>
</Header>
</Structure>
My interpretation of the problem is that the StructureType class
generated by xjc does not contain any reference whatsoever to the
StructureHeaderType class, so that, when encountering the Header
element, the
marshaller has no other choice than using the abstract HeaderType
class.
Do you guys have any idea of a workaround that would not involve
modifying the generated code ?
Cheers,
Luke