Install plugin failed for es 2.1.1

I write a plugin for es 2.1.1, but when i install the plugin, some error tell me not success instatl.
the error is

Trying file:/opt/meituan/ ...
Downloading .DONE
Verifying file:/opt/meituan/ checksums if available ...
NOTE: Unable to verify checksum for downloaded plugin (unable to find .sha1 or .md5 file to verify)
ERROR: Could not find plugin descriptor '' in plugin zip

my plugin project structure is

and my install code is

./plugin install file:///opt/meituan/

my plugin's java code is very simple

how can i fix the problem? thank you

I guess it's a packaging issue.
I'd move this file to src/main/resources so it will be packaged in your zip