Your plug-in should extend the AbstractExporterPlugin class:

public class HelpExporter
	extends AbstractExporterPlugin
	implements InteractivePlugin

You need to implement the InteractivePlugin.getRequestInformation() method. Use the getSaveAsParameter() and getOverwriteParameter() methods defined in the superclass to create plug-in parameters that asks for the file name to save to and if existing files can be overwritten or not. You should also check if the administrator has enabled the immediate execution functionality for your plug-in. If not, the only option is to export to a file in the BASE file system and the filename is a required parameter.

// Selected parts of the getRequestConfiguration() method
...
List<PluginParameter<?>> parameters = 
   new ArrayList<PluginParameter<?>>();
...
PluginDefinition pd = job.getPluginDefinition();
boolean requireFile = pd == null ? 
   false : !pd.getAllowImmediateExecution();

parameters.add(getSaveAsParameter(null, null, defaultPath, requireFile));
parameters.add(getOverwriteParameter(null, null));

configureJob = new RequestInformation
(
   Request.COMMAND_CONFIGURE_JOB,
   "Help exporter options",
   "Set Client that owns the helptexts, " +
     "the file path where the export file should be saved",
   parameters
);
....
return configureJob;

You must also implement the configure() method and check the parameters. If no filename has been given, you should check if immediate exection is allowed and set an error if it is not. If a filename is present, use the pathCanBeUsed() method to check if it is possible to save the data to a file with that name. If the file already exists it can be overwritten if the OVERWRITE is TRUE or if the file has been flagged for removal. Do not forget to store the parameters with the storeValue() method.

// Selected parts from the configure() method
if (request.getParameterValue(SAVE_AS) == null)
{
   if (!request.isAllowedImmediateExecution())
   {
      response.setError("Immediate download is not allowed. " + 
         "Please specify a filename.", null);
      return;
   }
   Client client = (Client)request.getParameterValue("client");
   response.setDownloadImmediately("Export help texts for client application " + 
     client.getName(), ExecutionTime.SHORTEST, true);
}
else
{
   if (!pathCanBeUsed((String)request.getParameterValue(SAVE_AS), 
      (Boolean)request.getParameterValue(OVERWRITE)))
   {
      response.setError("File exists: " + 
         (String)request.getParameterValue(SAVE_AS), null);
      return;
   }
   storeValue(job, request, ri.getParameter(SAVE_AS));
   storeValue(job, request, ri.getParameter(OVERWRITE));
   response.setDone("The job configuration is complete", ExecutionTime.SHORTEST);
}

Implement the performExport() method. This is defined as abstract in the AbstractExporterPlugin class. It has the same parameters as the ImmediateDownloadExporter.doExport() method and they have the same meaning. The only difference is that the out stream can be linked to a file in the BASE filesystem and not just to the HTTP response stream.

Optionally, implement the begin(), end() and getSuccessMessage() methods. Theese methods do nothing by default.