jaxb - 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:

<xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema">

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

  <xs:complexType name="Group">
    <xs:sequence>
      <xs:element name="caption" type="xs:string" minOccurs="0"/>
      <xs:element name="parameters" type="Parameter" nillable="true" minOccurs="0" maxOccurs="unbounded"/>
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="Parameter">
    <xs:sequence>
      <xs:element name="key" type="xs:string" minOccurs="0"/>
      <xs:element name="group" type="Group" minOccurs="0"/>
      <xs:element name="value" type="xs:string" minOccurs="0"/>
    </xs:sequence>
  </xs:complexType>
</xs:schema>

After new or modified schema appears it is automatically parsed by Schema compiler, java sources being generated, compiled and packaged into user jars:

  SchemaCompiler sc = XJC.createSchemaCompiler();
  // Input source for schema
  InputSource is = new InputSource(new StringInputStream(objectPackage.getObjectSchema()));
  // Parse
  sc.parseSchema(is);
  S2JJAXBModel model = sc.bind();
  // Generate source
  JCodeModel jCodeModel = model.generateCode(null, null);
  jCodeModel.build(packageSourceDirectory);
  // Compile and package 
  // ......

And everything was ok until it was decided that all user-generated classes must extend one specific known class, say UserRootObject:

package user.abc;
public class Group extends com.mycompany.xml.UserRootObject {
  //
}

and

package user.abc;
public class Parameter extends com.mycompany.xml.UserRootObject {
  //
}

Everything is on the fly, I can not force users to modify their schema files but I can transform them prior to code generation. Looks like I have two options to introduce that UserRootObject: somehow via JCodeModel or somehow transforming schema files before building Java sources.

Answer 1

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?