What is REST

REST is Representational State Transfer which helps two systems to talk to each other with a common programmatic language. Rest is a successful replacement for HTTP.

Integration in Salesforce can be done in the following steps: –

1) Configuration.
2) Call out.
3) Web services.

1) Configuration: –

Configuration is a process that is needed in Salesforce as well as in the external system.
Configuration in salesforce provides the endpoint of the external system with which integration needed to be done. We need to create a site and connected app for configuration.

2) Call out: –

It contains three classes which have respective methods to perform respective functions to interact with the other systems.

A) HTTP: -We use this class to initiate the http request and http response.

B) HTTP request: –
This make use of HTTP verbs: get (), post (), put (), delete (). These are the methods which indicate the functionality to be executed by the request method i.e. the type of request such insert, delete or update records to be made in the other system.

c) HTTP response:
This is the class which helps to handle the response send by the external systems (HTTP.send () operation)

3) Web services: –

We can write our own custom web service through apex code, which an external environ can invoke and the external environ can access our code and force.com application.

It has two methods Rest services () and Rest response ().

Integration can be done with SOAP also but REST is preferred over SOAP as it is light weighted, supports XML and Jason unlike Soap which supports only Xml.