Resolve an issue with the servlet mapping for JSR 356

[fenik17]

After some digging about #2316 (and #2326) I came to a conclusion that servlet mapping with trailing slash is incorrect in JSR 356 [1]. The mapping value must have a leading '/' and should not contain empty parts:

The value attribute must be a Java string that is a partial URI or URI-template (level-1), with a leading
‘/’. For a definition of URI-templates, see [6]. The implementation uses the value attribute to deploy the
endpoint to the URI space of the websocket implementation. The implementation must treat the value as relative to the root URI of the websocket implementation in determining a match against the request URI of an incoming opening handshake request. [WSC-4.1.1-2] The semantics of matching for annotated endpoints is the same as was defined in the previous chapter. The value attribute is mandatory; the implementation must reject a missing or malformed path at deployment time [WSC-4.1.1-3].

The trailing slash can be ignored or treated as missed part, as we saw in a Tomcat's implementation (#2320). Up to #2316 everything worked correctly: the /mapping/ was cleared on /mapping and were not registering templates with trailing slash.

This PR:

• Reverts Register websocket endpoints for /mapping/ for /mapping/* servlets #2316 (for master brach).
• Fixes a regexp for the servlet path cleaning: remove an unclosed character class.
• Allows '+' as part of servlet path segment (see [2]).
• Adds more test cases for the fixed regexp.

[1] https://jcp.org/aboutJava/communityprocess/mrel/jsr356/index.html
[2] https://www.w3.org/Addressing/URL/url-spec.txt

[fenik17]

@Artur- PTAL. Maybe I'm wrong?

[jfarcand]

See #2202

[Artur-]

Sorry for the lack of response. I do not think the regexp helps as it is about finding the servlet path but my problem was in what happens after that

[fenik17]

@Artur- yep, regexp do not affect for your issue. Can you describe the core problem that you are trying to solve?