Might be the POI jar compatibility issue with JDK (as per the details, but not sure unless I test it myself), can you download jar as per your JDK version and note that I do not have 9.7 IS installation setup currently to test, the code posted on the forum was tested on IS 10.4 with JDK 1.8.
POI 4.0 and later require JDK version 1.8 or later.
POI 3.11 and later 3.x versions require JDK version 1.6 or later.
POI 3.5 to 3.10 required the JDK version 1.5 or later. Versions prior to 3.5 required JDK 1.4+.
For more quesitons, feel free to write me an email.
#webMethods#Integration-Server-and-ESB