Consuming Salesforce REST API

Following is step by step guide for inbound API integration

Create a connected app.

On click of "New Connected App" button, fill following details:

Click Edit==>Manage==>Edit Policies and set Timeout to 24 hours.

Generate access token URL:

https://test.salesforce.com/services/oauth2/token     (Sandbox)

https://login.salesforce.com/services/oauth2/token   (Production)

Method: POST

Header:  Content-Type = application/x-www-form-urlencoded

In Body:

grant_type=password&client_id=<Consumer_key_from_ConnectedApp>&client_secret=<Consumer_Secret_from_ConnectedApp>&username=<username of sf org>&password=<password of sf org+security token>

Following is the response:

Use this access token in API consumption

Following are example REST API on Account object:

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

    @HttpDelete
    global static void doDelete() {
        RestRequest req = RestContext.request;
        RestResponse res = RestContext.response;
        String accountId = req.requestURI.substring(req.requestURI.lastIndexOf('/')+1);
        Account account = [SELECT Id FROM Account WHERE Id = :accountId];
        delete account;
    }
  
    @HttpGet
    global static Account doGet() {
        RestRequest req = RestContext.request;
        RestResponse res = RestContext.response;
        String accountId = req.requestURI.substring(req.requestURI.lastIndexOf('/')+1);
        Account result = [SELECT Id, Name, Phone, Website FROM Account WHERE Id = :accountId];
        return result;
    }
  
  @HttpPost
    global static String doPost(String name,
        String phone, String website) {
        Account account = new Account();
        account.Name = name;
        account.phone = phone;
        account.website = website;
        insert account;
        return account.Id;
    }
}

This is how to consume these API's

Test GET Method

The Header of the actual callout will be: -  
Authorization: Bearer <access_token>
URL
https://virajlearningsf1-dev-ed.my.salesforce.com/services/apexrest/Account/<account id>
Following would be the response:
{
    "attributes": {
        "type": "Account",
        "url": "/services/data/v47.0/sobjects/Account/0017F00000I8KqPQAV"
    },
    "Id": "0017F00000I8KqPQAV",
    "Name": "Grand Hotels & Resorts Ltd",
    "Phone": "(312) 596-1000",
    "Website": "www.grandhotels.com"
}
Test POST Method

Headers:

URL

https://virajlearningsf1-dev-ed.my.salesforce.com/services/apexrest/Account

Following is the raw body of callout

{ "name" : "Wingo Ducks", "phone" : "707-555-1234", "website" : "www.wingo.ca.us" }

Response would be account id of account just created.

Test Delete Method:

The Header of the actual callout will be: -  
Authorization: Bearer <access_token>
URL
https://virajlearningsf1-dev-ed.my.salesforce.com/services/apexrest/Account/<account id>
Select Method as DELETE.
This would delete the account who's id is passed in URL 
To make this integration Wrapper based, which is recommended to make it generic,
following changes need to be made.
1] Create a utility class
Global class APIUtility {
    public APIUtility() {

    }
    Global class Wrapper {
        public String name;
        public String phone;
        public String website;
    }
}
2] Update post method to use wrapper instead of separate parameters
@HttpPost
global static String doPost(APIUtility.Wrapper Data) {
	if(Data != null)    {
		Account account = new Account();
		account.Name = Data.name;
		account.phone = Data.phone;
		account.website = Data.website;
		insert account;
		return account.Id;
	}
   return '';
}
3] Pass following in body while consuming API
{
	"Data" :{
			"name" : "Wingo Ducks",
			"phone" : "707-555-1234",
			"website" : "www.wingo.ca.us"
		}
}