[castor-dev] deriveByClass for XML Attributes

[Stephen Bash]

Everyone-
I recently ran across a situation where it would be beneficial to use 
auto-naming for attributes (rather than elements), and I was wondering 
if this had ever come up before (I didn't find anything in the list 
archives).

As motivation, consider the following example:
public class DataContainer
{
    private Map data;
    public Map getData()
    {
        return data;
    }
    public void setData( Map data )
    {
        this.data = data;
    }
}
The following code instantiates the above class and then marshals it out 
(error handling removed):

public class DataToXML
{
    public static void main( String[] args )
    {
        HashMap mapData = new HashMap();
        mapData.put( "Boolean1", new Boolean( true ) );
        mapData.put( "String1", "Test1" );
        mapData.put( "Boolean2", new Boolean( false ) );
        mapData.put( "String2", "Test2" );
        DataContainer myData = new DataContainer();
        myData.setData( mapData );
        Mapping myMap = new Mapping();
        myMap.loadMapping( "dataContainerMap.xml" );
        Marshaller m1 = new Marshaller( new FileWriter( "myData.xml") );
        m1.setMapping( myMap );
        m1.marshal( myData );
    }
}
Following is what I would like (note: this probably also involves the 
bug with deriveByClass and the location attribute):

<DataContainer>
  <DataMap>
    <DataEntry dataKey="Boolean1" boolean="true" />
    <DataEntry dataKey="String1" string="Test1" />
    <DataEntry dataKey="Boolean2" boolean="false" />
    <DataEntry dataKey="String2" string="Test2" />
  </DataMap>
</DataContainer>
Currently, when I specify node="attribute" and 
auto-naming="deriveByClass" I get a NPE as follows (note: in this case I 
am not using the location attribute as it is a known bug):

java.lang.NullPointerException
	at 
org.apache.xml.serialize.XMLSerializer.startElement(XMLSerializer.java:421)
	at 
org.exolab.castor.xml.util.DocumentHandlerAdapter.startElement(DocumentHandlerAdapter.java:197)
	at org.exolab.castor.xml.Marshaller.marshal(Marshaller.java:1327)
	at org.exolab.castor.xml.Marshaller.marshal(Marshaller.java:1543)
	at org.exolab.castor.xml.Marshaller.marshal(Marshaller.java:782)
	at DataToXML.main(DataToXML.java:51)
Exception in thread "main"

The complete mapping file is below:
<?xml version="1.0"?>
<!DOCTYPE mapping PUBLIC "-//EXOLAB/Castor Object Mapping DTD Version 
1.0//EN" "http://castor.exolab.org/mapping.dtd";>

<mapping>
  <class name="DataContainer">
    <map-to xml="DataContainer" />
    <field name="data" collection="map">
       <bind-xml name="DataEntry">
         <class name="org.exolab.castor.mapping.MapItem">
           <field name="key" type="string">
             <bind-xml name="dataKey" node="attribute"/>
           </field>
           <field name="value">
             <bind-xml auto-naming="deriveByClass" node="attribute" />
           </field>
         </class>
       </bind-xml>
    </field>
  </class>
</mapping>
Any comments or suggestions would be greatly appreciated.  Thanks for 
you time.

Stephen

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