You most certainly don't need the Servlet API 2.2, the package should
build against libservlet-api-java (Servlet API 4.0) with minor
adjustments (if any).
Actually I did that initially and even tried to "fix it" but that went much
above my skills and interest. Enough to prefer engaging in making the package
for api 2.2 and searching its source code (which was not an easy part).
Actually many functions of servlet >= 2.3 are not implemented in jigsaw. Build
fails with any servlet-api version >= 2.3. Would anyone try to fix/patch it?
The package on my salsa repo would be a good starting point since it builds
fine with the bin:libjakarta-servletapi-2.2-java package installed, otherwise
sources (without the debian part) can taken from:
https://github.com/tenzap/jigsaw (branch with-jdk21).