XSD Schema that JAXB would find acceptable - xsd

Question

I have a REST XML response that has a chunk of data like this:
<tag>
<total-pages type="integer">5</total-pages>
<previous-page nil="true"></previous-page>
<next-page nil="true"></next-page>
<offset type="integer">5</offset>
</tag>
Now, sometimes the data can come back like this:
<tag>
<total-pages type="integer">5</total-pages>
<previous-page type="integer">0</previous-page>
<next-page type="integer">1</next-page>
<offset type="integer">5</offset>
</tag>
I have been trying to come up with a XSD schema structure that will account for both possibilities that would be acceptable to JAXB.
I have tried:
<tag>
<total-pages type="numeric-type" />
<previous-page type="numeric-type" />
<next-page type="numeric-type" />
<offset type="numeric-type" />
</tag>
<xsd:complexType>
<xsd:simpleContent>
<xsd:extension base="xsd:integer">
<xsd:attribute type="xsd:string" name="type" use="optional">
<xsd:attribute type="xsd:boolean" name="nil" use="optional">
</xsd:extension>
</xsd:simpleContent>
</xsd:complexType>
but JAXB blows up with an unmarshalling error.
Thoughts on what XSD schema structure I could use to account for the variability in the returning XML (I cannot change the XML, it is coming from a third-party which I have no control).
Thank you,
Perry

Answer 1

I've started by generating one XSD from your XML samples (two in your case):
<?xml version="1.0" encoding="utf-8"?>
<!--XML Schema generated by QTAssistant/XML Schema Refactoring (XSR) Module (http://www.paschidev.com)-->
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="tag">
<xs:complexType>
<xs:sequence>
<xs:element name="total-pages">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:unsignedByte">
<xs:attribute name="type" type="xs:string" use="required" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="previous-page">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string">
<xs:attribute name="type" type="xs:string" use="optional" />
<xs:attribute name="nil" type="xs:boolean" use="optional" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="next-page">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string">
<xs:attribute name="type" type="xs:string" use="optional" />
<xs:attribute name="nil" type="xs:boolean" use="optional" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="offset">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:unsignedByte">
<xs:attribute name="type" type="xs:string" use="required" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
When you compare with your XSD, you'll notice the use of string instead of integer as the base type. Which explains why you have a problem with unmarshalling: an empty string is not a valid number.
If instead of "nil" you would get an xsi:nil attribute, the XSD would've been generated differently, i.e. it would've had nillable="true" for your elements.
Since you cannot change the XML, then you're stuck with the use of string; alternatively, you could create a union between an empty string and a numeric value... as to how that'll look in JAXB, you can try it...