With all the features XML schema provides and JAXB translates you might think that including arbitrary Java objects in an XML document won't ever be necessary. But the need does arise occasionally. Special dumps of application data, for instance, may have to use this rather extreme technique. All in all, it is surprisingly simple, provided that the class of the object implements the java.util.Serializable interface. The schema element that is to contain the serialized binary data should be declared with a type of xsd:hexBinary. The schema snippet shows a simple container for some such object.

<xsd:complexType name="JavaObjectType">
  <xsd:sequence>
    <xsd:element name="data" type="xsd:hexBinary"/>
  </xsd:sequence>
</xsd:complexType>

<xsd:element name="container" type="JavaObjectType"/>

JavaObjectType makePojoElem( ObjectFactory objFact, Object pojo )
    throws IOException {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    ObjectOutputStream ooStream = new ObjectOutputStream( baos );
    ooStream.writeObject( pojo );
    ooStream.flush();
    JavaObjectType joElem = objFact.createJavaObjectType();
    joElem.setData( baos.toByteArray() );
    ooStream.close();
    return joElem;
}

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<container xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="serial.xsd">
    <data>ACED00057372...7878</data>
</container>

The reverse process is even simpler. The byte array returned by the getter for the data element is fed to the ObjectInputStream which smartly returns the original object.

Object getPojo( JavaObjectType joElem )
    throws IOException, ClassNotFoundException {
    ByteArrayInputStream bais = new ByteArrayInputStream( joElem.getData() );
    ObjectInputStream oiStream = new ObjectInputStream( bais );
    Object pojo = oiStream.readObject();
    oiStream.close();
    return pojo;
}