When trying to create an XSD subclass, JAXB/XCJ bawks:

...
    <xsd:complexType name="AuditInfo">
        <xsd:sequence>
            <xsd:element name="createId" type="xsd:long" />
            <xsd:element name="createTime" type="xsd:date" />
            <xsd:element name="modifyId" type="xsd:long" />
            <xsd:element name="modifyTime" type="xsd:date" />
        </xsd:sequence>
    </xsd:complexType>

    <!-- Project within Archer -->
    <xsd:complexType name="Study">
        <xsd:complexContent>
            <xsd:extension base="tns:AuditInfo">
                <xsd:sequence>
                <xsd:element name="id" type="xsd:long" />
                <xsd:element name="name" type="xsd:string" />
...

Error:

...
[ERROR] XJC while compiling schema(s): org.xml.sax.SAXParseException: A class/interface with the same name "au.edu.archer.schemas.icat.AuditInfo" is already in use. Use a class customization to resolve this conflict.
...
java.lang.NullPointerException    at com.sun.tools.xjc.util.Util.equals(Util.java:67)    at com.sun.tools.xjc.util.CodeModelClassFactory.createClass(CodeModelClassFactory.java:130)