I don't think I've ever had a problem with this.
If you put the class in a "common-lib" Netbeans Java Library project, and then make your WAR(s) dependent on that project (using the project library properties), NB should package the jar in the "right place".
In an EAR, the jar would be placed within the EAR itself, even tho it's used by the WAR (assuming there are no TLDs in the lib).
If you deploy the WAR alone, it will be package in WEB-INF/lib.
Either way it should Just Work.
Make sure your jar file is in one of those two places in your exploded EAR file.
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