JAXB binding to generate abstract Java class from non-abstract XML type

I ended up creating an XJC plugin . Here's the code:

import java.lang.reflect.Method;

import javax.xml.namespace.QName;

import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXException;

import com.sun.codemodel.JMod;
import com.sun.codemodel.JMods;
import com.sun.tools.xjc.Options;
import com.sun.tools.xjc.outline.ClassOutline;
import com.sun.tools.xjc.outline.Outline;
import com.sun.tools.xjc.reader.xmlschema.bindinfo.BIDeclaration;
import com.sun.tools.xjc.reader.xmlschema.bindinfo.BindInfo;
import com.sun.xml.xsom.XSAnnotation;

public class AbstractModifierPlugin extends com.sun.tools.xjc.Plugin {

    private static final QName ABSTRACT_QNAME = new QName("http://www.example.com/jaxb/abstract-modifier/1-0", "abstract");

    private static final String SET_FLAG_METHOD_NAME = "setFlag";

    private static final String OPTION_NAME = "Xabstract-modifier";

    @Override
    public String getOptionName() {
        return OPTION_NAME;
    }

    @Override
    public String getUsage() {
        return " -" + OPTION_NAME + " : marks as abstract the generated classes corresponding to XML types marked with "
                + "<xs:annotation><xs:appinfo><" + ABSTRACT_QNAME + "/></xs:appinfo></xs:annotation>";
    }

    @Override
    public boolean run(Outline outline, Options options, ErrorHandler errorHandler) throws SAXException {
        Method setFlagMethod = null;
        try {
            // There is no method to make a class abstract; we can only use setFlag, which is private, so
            // we must get it via reflection and make it accessible.
            setFlagMethod = JMods.class.getDeclaredMethod(SET_FLAG_METHOD_NAME, int.class, boolean.class);
            setFlagMethod.setAccessible(true);
        } catch (Throwable e) {
            System.err.println("There was an error retrieving the " + JMods.class.getName() + "." + SET_FLAG_METHOD_NAME
                    + " method (see below) => it will not be possible to set any class' abstract flag => this plugin will abort");
            e.printStackTrace();
            return false;
        }

        for (ClassOutline classOutline : outline.getClasses()) {
            if (hasAbstractAnnotation(classOutline)) {
                try {
                    setFlagMethod.invoke(classOutline.implClass.mods(), JMod.ABSTRACT, true);
                } catch (Throwable e) {
                    System.err.println("It was not possible to make " + classOutline.implClass.fullName()
                            + " abstract (see below)");
                    e.printStackTrace();
                }
            }
        }
        return true;
    }

    protected boolean hasAbstractAnnotation(ClassOutline classOutline) {
        XSAnnotation annotation = classOutline.target.getSchemaComponent().getAnnotation();
        if (annotation != null) {
            Object innerAnnotation = annotation.getAnnotation();
            if (innerAnnotation instanceof BindInfo) {
                for (BIDeclaration bindInfoDeclaration : (BindInfo) innerAnnotation) {
                    if (ABSTRACT_QNAME.equals(bindInfoDeclaration.getName())) {
                        return true;
                    }
                }
            }
        }
        return false;
    }

}

      

        
        
        
      

    

Here abstract.xsd

's which defines the element <abstract>

to be used to indicate that the generated class should be abstract:

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://www.example.com/jaxb/abstract-modifier/1-0"
    xmlns:tns="http://www.example.com/jaxb/abstract-modifier/1-0"
    elementFormDefault="qualified">

    <element name="abstract"/>

</schema>

      

        
        
        
      

    

Usage (after the example in my original question):

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    ...
    xmlns:abstract="http://www.example.com/jaxb/abstract-modifier/1-0"
    ...>

    <xs:complexType name="myAbstractType" abstract="true">
        <xs:annotation>
            <xs:appinfo>
                <jxb:class implClass="my.package.impl.MyAbstractClass"/>
            </xs:appinfo>
        </xs:annotation>
        ...
    </xs:complexType>

    <xs:complexType name="myAType">
        <xs:annotation>
            <xs:appinfo>
                <jxb:class implClass="my.package.impl.MyAClass"/>
                <!-- This tells the AbstractModifierPlugin to make the
                generated class abstract -->
                <abstract:abstract/>
            </xs:appinfo>
        </xs:annotation>
        <xs:complexContent>
            <xs:extension base="myAbstractType">
                ...
            </xs:extension>
        </xs:complexContent>
    </xs:complexType>

    <xs:complexType name="myBType">
        <xs:annotation>
            <xs:appinfo>
                <jxb:class implClass="my.package.impl.MyBClass"/>
                <!-- This tells the AbstractModifierPlugin to make the
                generated class abstract -->
                <abstract:abstract/>
            </xs:appinfo>
        </xs:annotation>
        <xs:complexContent>
            <xs:extension base="myAbstractType">
                ...
            </xs:extension>
        </xs:complexContent>
    </xs:complexType>

      

        
        
        
      

    

I have to say that it was quite difficult for me to find all the necessary documentation to figure out how to do this. If I can find the time, I will post a longer explanation here; for now i hope that at least the code helps. Disclaimer: I don't know if this is the best way to do it, but the classes I had to rely on are so poorly documented (and IMHO not well designed) that they are the best I could think of.

Hope this helps. If anyone wants to use this code, go ahead.