Raw Json data in request in liferay web service

I am using liferay 6.2 & i have invoked few web services.The thing is that when passing parameters as form data it works fine, get the json response, but the issue is when pass parameters as raw data json form it gives error "message": "No JSON web service action associated with path /login/user-login and method POST for //happiness-portlet". I was trying these things through postman the tool in chrome.I want the my json web service should accept the json raw data in request.Needed urgently, if any one knows pls help, thanks.