We created a REST Service in Salesforce in our previous blog, and now we want to call the REST service from another application. Salesforce DO NOT allow using Basic Authentication (Username & Password) for incoming REST calls. This is still true even if you are calling from another Salesforce instance.  We have to use OAuth to authenticate to Salesforce.

OAuth (Open Authorization) is an open protocol to provide secured authorization. Here are the list of OAuth flows used while making REST API calls:

• Web server flow, where the server can securely protect the consumer secret. more…

• Username-password flow, where the application has direct access to user credentials. more…

• User-agent flow, used by applications that cannot securely store the consumer secret. more…

In this blog, we are using Username-password flow to make a call to a REST Service in Salesforce using OAuth. Please follow the steps below to set up the REST call:

1) Remote Site Settings

First you need to create two entries in remote site settings:

1. Enter the remote site Name, URL for Salesforce login https://login.salesforce.com
2. Create another remote site Name, URL for accessing Salesforce data https://instance.salesforce.com.

2) Create Connected App

Now we create a Connected App:

1. Go to Setup | Create | Apps.
2. Under Connected App, Click “New”.
3. Enter the name of Connected App and specify details as mentioned (in Screenshot) below.
4. Click Save.

Once you have created the Connected App, you will see the following screen with “Consumer Key” and “Consumer Secret”:

We can use the “Consumer Key” which will be a client_id and “Consumer Secret” as client_secret inside the body of the call to make the callout.

grant_type=password&client_id='+clientId+'&client_secret='+clientSecret+'&username='+username+'&password='+password

Apex Code:-

/* Class for getting account record from other salesforce org through rest api integration
by calling class and its method from other org*/

public class TestWebService{
    public TestWebService(){
                                //You will get "clientId","clientSecret" when creating connected app in salesforce
        String clientId = '3MVG9szVa2RxsqBYoWov5yC4I5MxFgDDe3.6Z1g__FlEYNOPY45vALm1kA5oCZuFkHYxCzm2A3SdSoxFpUNU3';
        String clientSecret = '7917982719268332943';

        //We can also store our username password in custom setting.
        String username='ajomon@apexcoder.com';//salesforce username 
        String password='*l2YzP2TxlvI';//EUe4eHjMxXb8UFco1SPcpsZL9';//salesforce password
        // Generating the Access Token
        HttpRequest req = new HttpRequest();
        req.setMethod('POST');
        req.setEndpoint('https://login.salesforce.com/services/oauth2/token');// this is the OAuth endpoint where this request will be hit
        req.setBody('grant_type=password&client_id='+clientId+'&client_secret='+clientSecret+'&username='+username+'&password='+password);
        
        Http http = new Http();
        HTTPResponse res = http.send(req);
        String str = res.getBody();
        wrapObj = (Wrapper)Json.deserialize(str,Wrapper.class);
        accessToken = wrapObj.access_token;
        instanceUrl = wrapObj.instance_url;
        methodGet();
    }
        
    // Retrieve the Contacts from the otehr org.
    public void methodGet(){
        HttpRequest req = new HttpRequest();
        req.setMethod('GET');
        //req.setEndpoint(wrapObj.instance_url+'/services/apexrest/Account/getAccountById?name=champaKAli');
        
        req.setEndpoint(wrapObj.instance_url+'/services/apexrest/AccountService');
        req.setHeader('Authorization', 'OAuth '+wrapObj.access_token);
        Http http = new Http();
        HTTPResponse res = http.send(req);
        
        System.debug('***Response***** ' + res.getBody());
        //---------------------Here ------------------
        /*JSONParser parser = JSON.createParser(res.getBody());
        do{
            parser.nextToken();
        }while(parser.hasCurrentToken() && !'records'.equals(parser.getCurrentName()));
            parser.nextToken();
        List<account> acc = (List<Account>) parser.readValueAs(List<Account>.class);*/
    }
    public Contact con {get;set;}
    public String s1 {get;set;}
    public String accessToken;
    public String instanceUrl;
    public Wrapper wrapObj{get;set;}
    // Wrapper Class to Store the value from the Jason.
    public class Wrapper{
        String id;
        String instance_url;
        String access_token;
        String issued_at;
        String signature;
    }
}

In the above code, we are using client_id and client_secret to authorize the external app.

We can also parse the response using parser classes.

We can execute the above code using developer console and print all the accounts in system.debug() :

TestWebService tw = new TestWebService();
tw.methodGet();

The Force.com REST API lets you integrate external system with Force.com applications using simple HTTP methods, in either XML or JSON formats, making this an ideal API for developing mobile applications or third party applications.

Following are the benefits of using the REST API in your integrations:

• Easy Access: Use standard HTTP method call-outs, available on every language and platform, to make requests and retrieve information from Force.com.
• Flexible formats: Request and response can flow in XML or JSON format.
• Standards-based security: Basic Authorization (Username/Password or SessionId), OAuth (Open Authorization) .
• Data model: Standard/custom objects are accessible using REST API.
• Very lightweight and easy to use as compared to SOAP based services.

Let’s create an Apex REST Services which can perform insert, update, delete records .  In the below example, we are querying, creating, updating and deleting Accounts by implementing a Rest-Based Service called AccountService.

Note: For updating and deleting Accounts, developer must pass the parameters while making a REST call.

Creating REST Service

@RestResource(urlMapping='/AccountService/*')
global class AccountService {

 @HttpGet
 global static List<Account> getAccounts() {
   List<Account> Accounts = [SELECT Id,Name from Account LIMIT 10];
   return Accounts;
 }

 @HttpPost 
 global static String createNewAccount(String Name) {
   Account a = new Account();
   a.Name = Name;
   insert a;

   return 'Account Created';
 }

 @HttpDelete
 global static String deleteAccountById() {
 
   RestRequest req = RestContext.request;
   String Id = req.params.get('Id');

   List<Account> a = [ Select ID from Account where Id= :Id];

   delete a;

   return 'Account Deleted';
 }

 @HttpPut
 global static String updateAccount(String Id, String NewName) {
   Account a = [ Select ID, Name from Account where Id= :Id];
   a.Name = NewName;
   update a;

   return 'Account Updated';
 }
}

In the above code,

1. The REST service must be declared as global and static
2. The keyword “@RestResource”  is used to signify that class should act as REST based web service.
3. The urlMapping  property allows us to set path where the service will be available. This is how we set up the endpoint for the service. e.g.   https://.salesforce.com/services/apexrest/AccountService
4. There are few http methods mentioned:-
   1. @HttpGet  – returning data using HTTP GET request.
   2. @HttpPut  – updating data using HTTP POST request.
   3. @HttpDelete –  deleting data using HTTP DELETE request.
   4. @HttpPost – inserting data using HTTP PUT request.
   5. @HttpPatch – upserting data using HTTP PUT request.
5. In order to pass parameters to service,  we use RestRequest object in a method. See below sample code:

6. RestRequest req = RestContext.request;
    String Id = req.params.get('Id');

Using REST Service

Invoke REST Service from Workbench : 

1. login into workbench using below URL: https://workbench.developerforce.com/login.php
2. From the menu , please choose utilities > click REST Explorer

• GET – To get all the Accounts using @HttpGet

1. Select HTTP GET  method from radio buttons.
2. Enter the REST URI in the text box.
3. We are making a HTTP GET call to retrieve all the accounts.
4. Click on execute.
5. Click on “Show Raw Response”.

• Response Format: In the above screenshot, we can get response in XML or JSON by Clicking on “Headers” button and setting HTTP header with below code:

• Content-Type: application/xml
  accept: application/xml

• POST – To create an Account using @HttpPost

1. Select HTTP POST method from radio buttons.
2. Enter the REST URI in the text box.
3. We are making POST call, so enter a body in JSON format.
4. Click on execute, and see the raw response.

• Delete an Account using @HttpDelete

1. Select HTTP DELETE method from the radio buttons.
2. Pass the account id as a parameter:
   /services/apexrest/AccountService?id=00141000009K7xLAAS
3. Click on execute, and see the raw response.

Invoke REST SERVICE from APEX :

First you need to add the REST endpoint under Salesforce “Remote Site Settings”. To add the remote site settings, please follow the below steps:

1. From Setup, enter Remote Site Settings in the Quick Find box, then select Remote Site Settings.
2. Click New Remote Site.
3. Enter Remote Site Name.
4. Enter the URL for REST Service endpoint.
5. Click Save.

Once the remote site setting is setup, now we can invoke our rest service using apex.

Call REST Service using OAuth

Now rest service is ready to be called from anywhere. In the following example,  we are making an external callout to our REST service using OAuth Session Id and we are using below endpoint, which is the following format: https://instance.salesforce.com/services/apexrest/Class_Name

We are hitting following end point from APEX https://na35.salesforce.com/services/apexrest/AccountService

public class RestServiceClass{
 
 @future (callout=true)
 public static void RestServiceMethod(String sessionId){

 HttpRequest req = new HttpRequest();
 req.setEndpoint('https://na35.salesforce.com/services/apexrest/AccountService');
 req.setMethod('GET'); 
 req.setHeader('Authorization', 'OAuth ' + sessionId);
 req.setHeader('Content-Type','application/json'); 
 req.setTimeout(120000);
 
  
 HttpResponse res = new HttpResponse();
 res = http.send(req);
 
 system.debug(res);
 }

Other Considerations:

• We can set the Content-Type on the request header to Json or XML to get the results in respective formats.

• If you have many records to process, consider using Bulk API, which is based on REST principles and optimized for large sets of data.
• API Call limits to Salesforce will be enforced. Please see the link below:

https://developer.salesforce.com/docs/atlas.en-us.salesforce_app_limits_cheatsheet.meta/salesforce_app_limits_cheatsheet/salesforce_app_limits_platform_api.htm

For more information:

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_rest.htm

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_rest_code_samples.htm