[SalesForce] How to see JSON response for REST service

How I can see what the JSON response looks like for a REST service that looks like the one below? I guess I'm looking for the actual steps of what I need to do to see the JSON response.

@RestResource(urlMapping = '/BP_Routes/*')
global with sharing class BP_Routes {

    @HttpPost //Method name
    //Check for User Authentication based on UserName and Password from external system
    global static ResponseWrapper BP_Routes(string username) {

        String strStatusMsg = '';//Holds the status message
        Integer isSuccessRes;//Holds the success response '1' or '0'
        list<Routewrapper> lstRteWrap = new list<Routewrapper>();
        list<personRoutesWrapper> lstPrsnWrap = new list<personRoutesWrapper>();
        ...

Best Answer

You can head over Salesforce Workbench and use the REST Utility to test the endpoint .

enter image description here

Your endpoint to test will be

/services/apexrest/BP_Routes

Also looks like the method is accepting a string parameter ,so you will need to select post and then the JSON input is

{
  "username" : "test"
}

The response will tell you the JSON structure .Also just by looking into the ResponseWrapper class you will know the structure of the JSON .