How to set content type to be application/json?

You have 2 options:
– if you use the REST Resources then you can go to that method and define an representation for “request”, like in the below screenshot, this will make the application/json displayed in the drop down for that method:

– if you use the HTTP request then all u need to do is to open the request and just type the content they you want eg application/json, this will be available only for this request if you have more like this then you need to repeat this step:

Hope this will help you.