Improve validation for StringMatchFilter for null/empty text #3153

[JWT007]

This should fix a potential NPE in StringMatchFilter if the 'text' field is not set or set to null/empty string. #3153

• Added '@required' to @PluginAttribute
• removed default value of ""
• added notEmpty assert to Builder setText
• added notEmpty assert to StringMatchFilter constructor.
• added changelog XML file.

Checklist

• Base your changes on 2.x branch if you are targeting Log4j 2; use main otherwise
• ./mvnw verify succeeds (if it fails due to code formatting issues reported by Spotless, simply run ./mvnw spotless:apply and retry)
• Non-trivial changes contain an entry file in the src/changelog/.2.x.x directory
• Tests for the changes are provided
• Commits are signed (optional, but highly recommended)

[github-actions]

Job	Requested goals	Build Tool Version	Build Outcome	Build Scan®
build-macos-latest	clean install	3.9.8	✅
build-ubuntu-latest	clean install	3.9.8	✅
build-windows-latest	clean install	3.9.8	✅

Generated by gradle/develocity-actions

[ppkarwasz]

@JWT007,

Thank you for your contribution. Can you add some unit tests to the PR?

[JWT007]

Hi @ppkarwasz I looked to see if I could extend an existing test for StringMatchFilter but there were no existing unit-tests.

[ppkarwasz]

Hi @ppkarwasz I looked to see if I could extend an existing test for StringMatchFilter but there were no existing unit-tests.

Yes, it happens. 😉 Can you create a StringMatchFilterTest in the log4j-core-test module and test the two conditions you fixed (build() returns null if setMatchString is not called and setMatchString throws if null or an empty string is used as paramter).

[ppkarwasz]

LGTM, thanks!