how to force schema compiled classes to extend specific class outside schema

Question

Need help with following situation: Users can generate their own data structures which are stored as JAXB-ready XSD sources like below:

Answer 1

I do not believe that there is an easy way to do this using JAXB itself. There are a number of customization options available that are not commonly known - read section 7 of JSR222 for details.

If you have some control over the input schemas, then you might want to consider using XSLT to transform the schema. I believe that this can be done by using a javax.xml.transform.dom.DOMResult instance as the target of the transformation and using the output as a DOM tree (e.g., calling getNode() on the result) as the input to parseSchema. A basic transformation would be to replace:

<xs:complexType name="foo">
  <!-- CONTENTS -->
</xs:complexType>

with something like:

<xs:complexType name="foo">
  <xs:complexContent>
    <xs:extension base="UserRootObject">
      <!-- CONTENTS -->
    </xs:extension>
  </xs:complexContent>
</xs:complexType>

Of course this only works for the simple cases. If you already have inheritance in your schema files, then you will have to do some filtering in the XSLT that only applies this transform to types that do not already extend.

Answer 2

It is a bit an old topic, but just for the record:

You can do this with the jaxb2 inheritance plugin. Like this:

<xs:complexType name="...">
  <xs:annotation>
    <xs:appinfo>
      <inheritance:extends>
         com.mycompany.xml.UserRootObject
      </inheritance:extends>
    </xs:appinfo>
  </xs:annotation>
  <!-- ... -->
</xs:complexType>

See for example here http://vistaofjavahorizon.blogspot.com/2014/07/how-to-have-particular-java-class.html

There are more examples online.

Answer 3

XJC has an extension for this purpose

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
           xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
           jaxb:extensionBindingPrefixes="xjc"
           jaxb:version="2.0">

    <xs:annotation>
       <xs:appinfo>
          <jaxb:globalBindings>
           <xjc:superClass name="com.mycompany.xml.UserRootObject"/>
          </jaxb:globalBindings>
       </xs:appinfo>
    </xs:annotation>
.
.
.
</xs:schema>

For more information see:

• http://jaxb.java.net/nonav/2.0.2/docs/vendorCustomizations.html

The schema annotations can also be supplied via an external bindings file. For an example see:

• How do you customize how JAXB generates plural method names?

Answer 4

Many thanks to D.Shawley for pointing out the right section in JSR 222. Here is final solution which might be helpful and time saving for someone else. Original schema must be transformed as follows:

    <xs:schema version="1.0" 
               xmlns:xs="http://www.w3.org/2001/XMLSchema" 
               xmlns:jaxb="http://java.sun.com/xml/ns/jaxb" 
               jaxb:version="2.0" >

      <xs:element name="Group" type="Group"/>
      <xs:element name="Parameter" type="Parameter"/>


      <xs:complexType name="Group">
        <xs:complexContent>
          <xs:extension base="UserRootObject">
            <xs:sequence>
            <!-- params -->
            </xs:sequence>
          </xs:extension>
        </xs:complexContent>
      </xs:complexType>

      <xs:complexType name="Parameter">
        <xs:complexContent>
          <xs:extension base="UserRootObject">
            <xs:sequence>
            <!-- params -->
            </xs:sequence>
          </xs:extension>
        </xs:complexContent>
      </xs:complexType>

      <xs:complexType name="UserRootObject">
        <xs:annotation>
          <xs:appinfo>
            <jaxb:class name="UserRootObject" implClass="com.mycompany.xml.UserRootObject"/>
          </xs:appinfo>
        </xs:annotation>
      </xs:complexType>
    </xs:schema>

Transformation can be easily performed via org.w3c.dom.Document inteface.