Fix NPE when interface has spring mvc annotations

[bananayong]

This PR fix #477

Use Type instance directly, to prevent NPE.
classContext.getMethodGen(m) can return null, when interface is scanned.

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Spring cloud openfeign client uses spring mvc annotation, but these client are not controller.
These classes should be skipped for spring detectors.

[h3xstream]

Those OpenFeign interface could be use to implement web controller at the same time..
If it can reduce an important quantity of noise, I am ok with it.

• SpringMvcEndpointDetector.java is not critical.
• However, SpringEntityLeakDetector is very important. **

** Even-though, the code flagged is contain in a client project. It would actually identify something wrong on the back-end.

Have you seen false positive with the second detector (SpringEntityLeakDetector) ?

[bananayong]

I have not yet. But, You're right.

Client and server can share very same interface for consistency.
I don't think so it is good practice, because generally interface name for feign client includes XXXClient or RemoteXXXService. But It can be.

What about SpringEntityLeakDetector check only annotated class(@Controller, @RestController) and find @RequestMapping annotated methods(including superclasses and interfaces)?

It's not perfect solution Because Spring supports meta-annotations. But, I think it is best efforts.
Please, let me know your idea.

Thank you!

[h3xstream]

@bananayong I would simply remove this exception from the detector SpringEntityLeakDetector. There is something fishy if the client is reusing database classes as DTO.

[bananayong]

You mean that annotated methods should be reported whether it is for feign client or not, Right?
I agree.

Actually, My purpose was to resolve NPE. If NPE is resolved then I can exclude FeignClient through findBugs excludeFilter.xml.

I will modify my PR.
Please forget feign client checking logic.

[fsonntag]

@h3xstream Any plans on getting this merged and released? :)

[h3xstream]

I will integrate this change as I see it add a test case for the empty method (from interface).

Note: I will push in a moment a PR that makes changes to this detector to support generic and include some other refactoring to better support mass assignment detection.

[h3xstream]

The detector was refactored #496