Create or use a service that uses the java.io.File.list method. If you want to use a filter, for example to match filenames using wildcards, you can find the code to do that on the 'net.
The PSUtilities package, downloadable from Advantage, has a service to get a list of files and uses JZOOWildcardFilter for wildcard matching.
#webMethods-BPMS#MWS-CAF-Task-Engine#webMethods