got `null` pointerException when use --window-length-duration-ms

Describe the bug

I’d like to implement pulsar functions with –window-length-duration-ms realized only the class that inherited from java.util.function.Function class can do.

However, other function that inherited from this org.apache.pulsar.functions.api.WindowFunction throws exception Function class org.apache.pulsar.functions.api.examples.ContextWindowFunction does not implement the correct interface

other function that inherited from this org.apache.pulsar.functions.api.Function throws exception Exception in thread “main” java.lang.NullPointerException

Is there any specific reason why those two functions are not supported windowing feature? or if should work properly, can I find out any better examples with command line?

To Reproduce Steps to reproduce the behavior:

1. go to org.apache.pulsar.functions.api.examples.ContextWindowFunction in pulsar-function and run with --window-length-duration-ms 6000 or go to org.apache.pulsar.functions.api.examples.CustomDerivedToBaseFunction in pulsar-function and run with --window-length-duration-ms 6000

[wolfstudy]

@wolfstudy #6246 appears to be in 2.5.1 , so it’s in the release candidate now.

The #6246 will be cherry-pick to 2.5.1, when pulsar 2.5.1 is released, the issue will be fixed. And @tuteng is working this.

[qmnonic]

Looks like it was introduced in 2.4.1, by this PR - https://github.com/apache/pulsar/pull/4844 , issue shouldn’t exist in 2.4.0. Waiting for a binary build of 2.5.1-candidate-1 ( https://github.com/apache/pulsar/releases/tag/v2.5.1-candidate-1 ) or a way to build it, to validate.