[ZEPPELIN-6475] Throw clear error for missing InfluxDB token

[gyowoo1113]

What is this PR for?

InfluxDBInterpreter.open() read the influxdb.token property and immediately called toCharArray() on the returned value. When the token was not configured, getProperty(...) returned null, causing a NullPointerException without explaining that the authentication token was missing.

This PR validates the token before building the InfluxDB client. Missing, empty, and blank token values now throw an InterpreterException with a clear configuration message instead of a NullPointerException.

Unit tests were added for absent, empty, and whitespace-only token values. Other InfluxDB properties and client creation behavior are unchanged.

What type of PR is it?

Bug Fix

Todos

• Validate missing, empty, and blank influxdb.token values
• Throw InterpreterException with a clear error message
• Add unit tests for each invalid token case

What is the Jira issue?

ZEPPELIN-6475

How should this be tested?

./mvnw test -pl influxdb passes successfully.

To run only the interpreter test:

./mvnw test -pl influxdb -Dtest=InfluxDBInterpeterTest passes successfully.

Missing, empty, and blank influxdb.token values throw InterpreterException instead of NullPointerException.

Screenshots (if appropriate)

N/A

Questions:

• Does the license files need to update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No

[hyunw9]

LGTM

[hyunw9]

nit :
How about token.isBlank() instead? it covers same situations but it reads more clearly.

[gyowoo1113]

Good point, thanks! I’ve updated it to use isBlank().

[ParkGyeongTae]

Thanks for fixing this, @gyowoo1113! I pulled the branch and verified locally:

• Confirmed the NPE reproduces on master when influxdb.token is unset (getProperty(...).toCharArray() on a null value).
• The open() signature change to throws InterpreterException is safe — the parent Interpreter.open() already declares throws InterpreterException, so no callers are affected.
• String.isBlank() is fine here since the project targets Java 11.
• Ran ./mvnw test -pl influxdb -Dtest=InfluxDBInterpeterTest: all 5 tests pass (2 existing + 3 new for missing/empty/blank token).