Files.probeContentType(path) always return null

[jinyulei0710]

Jenkins and plugins versions report

Environment

Paste the output here

What Operating System are you using (both controller, and any agents involved in the problem)?

center os 7

Reproduction steps

1. add a file name a.html
2. execute upload
3. Files.probeContentType(path) return null

Expected Results

Files.probeContentType(path) return text/html

Actual Results

Files.probeContentType(path) return null

Anything else?

String filename = filePath.getName();
Path path = Paths.get(filename);

As the path is not the right path of the file,The result is always return null.