Salesforce Rest Api

Force.com REST API provides you with a powerful Web services API that you can use to interact with Force.com.

Each resource in REST API is a named URI that’s used with an HTTP method: HEAD, GET, POST, PATCH, or DELETE. All resources are accessed using a generic interface over HTTP with a base URI that follows your Force.com or Database.com URI. REST API supports authentication using OAuth 2.0 and supports both JSON and XML (JSON is the default).

To test the Salesforce Rest API. login to workbench. Navigate to utilities-> Rest Explorer and follow below examples to create/update/upsert/delete records. 

 Create a record:
Url:https://instance.salesforce.com/services/data/vNN.N/sobjects/sObject
Method:POST
Request Body:field-value pairs
eg:

url:https://ap1.salesforce.com/services/data/v37.0/sobjects/case
Request Body:{
"Origin": "SMS Feedback",
"Subject": "134350/Feedback",
"Description": "Payment Type: Credit Card "
}

Update a Record
Url:https://instance.salesforce.com/services/data/vNN.N/sobjects/sObject/Id 
Method:PATCH 
Request Body:field-value pairs 
eg:

url:https://ap1.salesforce.com/services/data/v37.0/sobjects/case/500260000045ffRAAQ
Request Body:{
"Origin": "SMS Feedback",
"Subject": "134350/Feedback",
"Description": "Payment Type: Credit Card "
}

Upsert a Record
Url:https://instance.salesforce.com/services/data/vNN.N/sobjects/sObject/externalIdField/value Method:PATCH 
Request Body:field-value pairs 
eg:

url:https://ap1.salesforce.com/services/data/v37.0/sobjects/case/externalfield__c/54364
Request Body:{
"Origin": "SMS Feedback",
"Subject": "134350/Feedback",
"Description": "Payment Type: Credit Card "
}

Delete a Record
https://instance.salesforce.com/services/data/vNN.N/sobjects/sObject/Id Method:DELETE 
eg:

url:https://ap1.salesforce.com/services/data/v37.0/sobjects/case/500260000045fesAAA

Bulk Data load integration across two different organizations

I tried the code which was posted in salesforce blogs
https://developer.salesforce.com/blogs/developer-relations/2015/07/using-apex-to-integrate-salesforce.html
I made some minor changes to trigger and the class to bulk load data between two different organizations.

Create Trigger on account object.

trigger SendAccount on Account(after insert)
{
 String jsonstr = JSON.serializePretty(Trigger.new);
 SendAccountUsingRESTAPI.callcreateAcc(jsonstr);
}

SendAccountUsingRESTAPI Apex Class

public class SendAccountUsingRESTAPI {
  private final String clientId = 'Client Id From Connected App';
   private final String clientSecret = 'clientSecret From Connected App';
   private final String username = 'User Name';
   private final String password = 'Password';
  public class deserializeResponse
   {
      public String id;
      public String access_token;
   }
  public String ReturnAccessToken (SendAccountUsingRESTAPI acount)
   {
      String reqbody = 'grant_type=password&client_id='+clientId+'&client_secret='+clientSecret+'&username='+username+'&password='+password;
     Http h = new Http();
      HttpRequest req = new HttpRequest();
      req.setBody(reqbody);
      req.setMethod('POST');
      req.setEndpoint('https://login.salesforce.com/services/oauth2/token');
      HttpResponse res = h.send(req);
      System.debug('\n Body Response:'+res.getbody());
      deserializeResponse resp1 = (deserializeResponse)JSON.deserialize(res.getbody(),deserializeResponse.class);
      return resp1.access_token;
   }
   
   @future(callout=true)
   public static void callcreateAcc(String jsonstr)
   {
      SendAccountUsingRESTAPI acount1 = new SendAccountUsingRESTAPI();
      String accessToken;
      accessToken = acount1.ReturnAccessToken (acount1);

       if(accessToken != null){
          String endPoint = 'https://ap1.salesforce.com/services/apexrest/v1/sampledemo/';

           Http h2 = new Http();
           HttpRequest req1 = new HttpRequest();
           req1.setHeader('Authorization','Bearer ' + accessToken);
           req1.setHeader('Content-Type','application/json');
           req1.setHeader('accept','application/json');
           req1.setBody(jsonstr);
           req1.setMethod('POST');
           req1.setEndpoint(endPoint);
           HttpResponse res1 = h2.send(req1);
        
           String trimmedResponse = res1.getBody().unescapeCsv().remove('\\');
           
           List<Account> accountsDeserialized = (List<Account>) JSON.deserialize(trimmedResponse, List<Account>.class);
           List<Account> lstAccount=new List<Account>();
           for(Account acc:accountsDeserialized){
               Account ac=new Account(Id=acc.Customer_ID__c);
               ac.Customer_ID__c=acc.Id;
               lstAccount.add(ac);
           }
           
           if(!lstAccount.isEmpty()){
               update lstAccount;
           }
        }
   }
}

In the Other Salesforce Org we need to created a rest web service. I create a sampledemo class

@RestResource(urlMapping='/v1/sampledemo/*')
global with sharing class sampledemo {

    @HttpPost
    global static String createAccount(){
        String requestBody = RestContext.request.requestBody.toString();
       // List<Account> accountsDeserialized = (List<Account>) JSON.deserialize(requestBody, List<Account>.class);
        //insert accountsDeserialized;
        List<Account> accountsDeserialized=new List<Account>();
        List<Object> m = (List<Object>)JSON.deserializeUntyped(requestBody);
        for(Object obj:m){
            Map<String,Object> requests = (Map<String,Object>)obj;
            Account acc=new Account();
            acc.Name=(String)requests.get('Name');
            acc.Customer_Id__c=(Id)requests.get('Id');
            accountsDeserialized.add(acc);
        }
        
        if(!accountsDeserialized.isEmpty()){
            insert accountsDeserialized;
        }
  
        String returnResponse = JSON.serialize(accountsDeserialized);
        return returnResponse;
    }
}

I tried the below code to load 3 accounts. It made 2 callouts(one for authentication and the other for data sync).

List<Account> lstAccount=new List<Account>();
for(Integer i=0;i<3;i++){
 Account acc=new Account();
 acc.Name= 'Test Sample'+i;
 lstAccount.add(acc);
}
insert lstAccount;

The response we get from the External org will be in JSON format. The response we are parsing and updating the customer id field.