NIFI-16241 Fix PublishAMQP handling of blank Routing Key

[ing-mattioni]

Summary

NIFI-16241

This pull request updates PublishAMQP to route FlowFiles to the failure relationship when the evaluated Routing Key is null, empty, or whitespace-only. This prevents invalid FlowFiles from being rolled back and repeatedly processed.

Changes

• Fix PublishAMQP handling of blank Routing Key

Tracking

Please complete the following tracking steps prior to pull request creation.

Issue Tracking

• Apache NiFi Jira issue created

Pull Request Tracking

• Pull Request title starts with Apache NiFi Jira issue number, such as NIFI-00000
• Pull Request commit message starts with Apache NiFi Jira issue number, as such NIFI-00000
• Pull request contains commits signed with a registered key indicating Verified status

Pull Request Formatting

• Pull Request based on current revision of the main branch
• Pull Request refers to a feature branch with one commit containing changes

Verification

• Added regression tests for missing, empty, and whitespace-only evaluated Routing Keys.
• Verified that affected FlowFiles are transferred to failure and removed from the input queue.
• Not run locally because Java/JAVA_HOME is not available in the environment.

Build

• Build completed using ./mvnw clean install -P contrib-check
  • JDK 21
  • JDK 25

Module-level verification performed:

.\mvnw.cmd -pl :nifi-amqp-processors -am test

Additional verification performed:

.\mvnw.cmd -pl :nifi-amqp-processors -am -P contrib-check install -DskipTests

.\mvnw.cmd -pl :nifi-amqp-nar -am install -DskipTests

Licensing

• New dependencies are compatible with the Apache License 2.0
• New dependencies are documented in applicable LICENSE and NOTICE files

No new dependencies were added.

Documentation

• Documentation formatting appears as expected in rendered files

No user-facing documentation files were changed.

[exceptionfactory]

@ing-mattioni Are you still working on this, or is it ready to review? Changing from throwing an exception to routing to failure alters the behavior in a notable way, so that needs some consideration.

[ing-mattioni]

@exceptionfactory for me it is ready to review but it is not a problem if you and the team decide that dhanging from throwing an exception to routing to failure is not acceptable as a change (in my use case it will be probably be better, but I undestand that in other scenarios it could be worse or not optimal)

[exceptionfactory]

Thanks @ing-mattioni. One straightforward option is to add the isBlank() check and throw the same exception, but not route to failure. It is arguable that lack of the Routing Key is a configuration problem, which makes the exception the more applicable approach. If input FlowFiles may or may not have the required attributes, it would be better to design the flow accordingly, using RouteOnAttribute or similar.