[Vtd-xml-developers] How can you insert into XML such as: <foo/>

[John S. <jsi...@al...>]

I am evaluating vtd-xml as a possible replacement for standard Java DOM
and XPath implementations. We have an XMLUtility which has methods to
insert structure into XML. I have done enough work to see that we can
get significant performance improvements with vtd-xml, but right off the
bat I hit this issue:

 

The following test illustrates that if the starting XML is <foo></foo>
that the method:

 

   private static String insert( String document, String xPath, String
node ) throws Exception

 

can be used to insert 'structure' into the XML. This is shown by:

 

        System.out.println(insert("<foo></foo>", "//foo", "bar"));

 

This does not insert 'structure':

 

        System.out.println(insert("<foo></foo>", "//bogus", "bar"));

 

That is correct behavior because the XPath //bogus is not found in the
starting XML (<foo></foo>).

 

The problem occurs with:

 

        System.out.println(insert("<foo/>", "//foo", "bar"));

 

 

 

 

import java.io.ByteArrayOutputStream;

 

import com.ximpleware.AutoPilot;

import com.ximpleware.ModifyException;

import com.ximpleware.VTDGen;

import com.ximpleware.VTDNav;

import com.ximpleware.XMLModifier;

 

public class Insert

{

 

    public static void main( String[] arguments ) throws Exception

    { 

        System.out.println(insert("<foo></foo>", "//foo", "bar"));

        System.out.println(insert("<foo></foo>", "//bogus", "bar"));

        System.out.println(insert("<foo/>", "//foo", "bar"));

 

    }

    

    /**

     * Insert a node into an existing document.

     * @param document

     * @param xPath

     * @param node

     * @return

     * @throws Exception

     */

    private static String insert( String document, String xPath, String
node ) throws Exception

    {

        VTDGen vg = new VTDGen();

        XMLModifier xm = new XMLModifier();

        vg.setDoc(document.getBytes());

        vg.parse(true);

        VTDNav vn = vg.getNav();

        AutoPilot ap = new AutoPilot(vn);

        xm.bind(vn);

        ap.selectXPath(xPath);

        int xmlIndex = ap.evalXPath();

       

        if ( xmlIndex > 0 )

        {

            try

            {

                xm.insertAfterHead("</"+node+">");

            }

            catch ( ModifyException me )

            {

                System.out.println("Failed to insert: "+node+" at index:
"+xmlIndex);

                throw me;

            }

        }

        ByteArrayOutputStream output = new ByteArrayOutputStream();

        xm.output(output);

        return output.toString();

    }

 

}