Hi Dhananjay,
If you have placed the jar and json in the artifact directory of CDAP, then the artifacts are automatically considered SYSTEM by CDAP and they available across all the namespaces. They will be loaded during the start of the system or you can use the API to trigger the load.
Here is the API to do so :
Note : you dont need load the individual artifact using REST if in artifact directory.
But, please remember that if you are in development stage of plugin this might be might not be an efficient way.
Another way is to deploy artifact as USER using the rest APIs in which case the jar and json can be in any directory. Using the API you would upload it to CDAP.
Could you please the list of files in the artifact directory ?
Thanks,