We would certainly consider it, especially if you were to provide docs and unit
tests alongside the code :)

It'd be best if the code was like <manifest>; it could also act as a self
contained task to create the relevant file outside the JAR itself. Some people
like that.

I had al look at the ANT 1.6.2 Sources and tis is my Idea:

package org.apache.tools.ant.taskdefs;

class Service
{
  private String type;
  private List providerList;

  setType(String type)...
  Provider createProvider()...
  //writing the File
  void write(ZipOutputStream zOut)
  {
     
  }
}

class Provider
{
 private String clazz;
 setClass(String clazz)...
}

class Jar ..
{
  private List serviceList = new LinkedList();

  ...

    protected void initZipOutputStream(ZipOutputStream zOut)
        throws IOException, BuildException {

        if (!skipWriting) {
            Manifest jarManifest = createManifest();
            writeManifest(zOut, jarManifest);
            writeService(zOut);//add this line
        }
    }

  public Service createService()
  {
    Service service = new Service();
    serviceList.add(service);
    return service;
  }

  private void writeService(ZipOutputStream zOut)
  {
     Iterator i = serviceList.iterator();
     while(i.hasNext())
     {
       ((Service) i.next()).write(zOut);
     }
  }
}

I will try to implement this.

Do you really need to use "createService()" instead of
 "addConfiguredService(Service s)" or any other of the "add..." methods.

The main difference between the two, is that "add..." would allow having
polimorphic usage of services, while "create..." does not.

If we eventually manage to do polimorphism, "add..." is a much better starting 
point.

Created attachment 12971 [details]
first impl.

Committed a slightly modified version of this.
Thanks for the patch!