Integration – REST API Questions

REST API Integration with Apex - Q&A

1. Q1. What is REST API and its key characteristics?
   Ans: REST (Representational State Transfer) is an architectural style that uses: - HTTP methods (GET, POST, PUT, DELETE) - Stateless communication - JSON/XML payloads - Resource-based URLs (e.g., /accounts/123)
2. Q2. How do you create a REST endpoint in Apex?
   Ans: Use @RestResource annotation:

   @RestResource(urlMapping='/contacts/*')
   global class ContactAPI {
     @HttpGet
     global static Contact getContact() {
       String contactId = RestContext.request.requestURI.substringAfterLast('/');
       return [SELECT Id, Name FROM Contact WHERE Id = :contactId];
     }
   }

3. Q3. What are the HTTP methods supported in Apex REST?
   Ans: Six supported methods: - @HttpGet - @HttpPost - @HttpPut - @HttpDelete - @HttpPatch - @HttpHead
4. Q4. How do you access request parameters?
   Ans: Three ways to access data:

   // 1. URL path parameter
   String id = RestContext.request.requestURI.substringAfterLast('/');
   
   // 2. Query parameter
   String name = RestContext.request.params.get('name');
   
   // 3. Request body (for POST/PUT)
   Map body = (Map)JSON.deserializeUntyped(
     RestContext.request.requestBody.toString()
   );

5. Q5. How do you set response headers and status codes?
   Ans: Use RestContext.response:

   @HttpGet
   global static void getData() {
     RestResponse res = RestContext.response;
     res.statusCode = 200;
     res.addHeader('Content-Type', 'application/json');
     res.responseBody = Blob.valueOf(JSON.serialize(myData));
   }

6. Q6. What is the process to expose Apex REST API?
   Ans: 3-Step Process: 1. Create class with @RestResource 2. Add methods with HTTP annotations 3. Access via /services/apexrest/urlMapping
7. Q7. How do you handle authentication in Apex REST APIs?
   Ans: Three approaches: 1. Session ID: Use current user's session 2. OAuth: Validate access tokens 3. Custom Token: Implement API keys
8. Q8. How do you test REST APIs in Apex?
   Ans: Test class structure:

   @isTest
   private class ContactAPITest {
     @isTest
     static void testGetContact() {
       Contact c = new Contact(LastName='Test');
       insert c;
       
       RestRequest req = new RestRequest();
       req.requestURI = '/services/apexrest/contacts/' + c.Id;
       req.httpMethod = 'GET';
       RestContext.request = req;
       
       Test.startTest();
       Contact result = ContactAPI.getContact();
       Test.stopTest();
       
       System.assertEquals('Test', result.LastName);
     }
   }

9. Q9. How do you handle errors in REST APIs?
   Ans: Standard error response pattern:

   @HttpGet
   global static void getData() {
     try {
       // Business logic
       RestContext.response.responseBody = Blob.valueOf(JSON.serialize(data));
     } catch(Exception e) {
       RestContext.response.statusCode = 500;
       RestContext.response.responseBody = Blob.valueOf(JSON.serialize(new Map{
         'error' => e.getMessage(),
         'stackTrace' => e.getStackTraceString()
       }));
     }
   }

10. Q10. How do you implement pagination?
    Ans: Use query parameters:

    @HttpGet
    global static List getAccounts() {
      Integer page = Integer.valueOf(RestContext.request.params.get('page'));
      Integer size = Integer.valueOf(RestContext.request.params.get('size'));
      
      return [SELECT Id, Name FROM Account 
              LIMIT :size OFFSET :(page * size)];
    }

11. Q11. How do you process bulk data in REST APIs?
    Ans: Chunking pattern:

    @HttpPost
    global static void createContacts() {
      List contacts = (List)JSON.deserialize(
        RestContext.request.requestBody.toString(),
        List.class
      );
      
      List results = Database.insert(contacts, false);
      // Process partial successes
    }

12. Q12. How do you version REST APIs?
    Ans: URL versioning best practice:

    @RestResource(urlMapping='/v1/accounts/*')
    global class AccountAPI_V1 { /*...*/ }
    
    @RestResource(urlMapping='/v2/accounts/*')
    global class AccountAPI_V2 { /*...*/ }

13. Q13. How do you secure REST endpoints?
    Ans: Security measures:

    @HttpGet
    global static void getSensitiveData() {
      // 1. Verify session
      if(Test.isRunningTest() == false && 
         RestContext.request.headers.get('Authorization') == null) {
        RestContext.response.statusCode = 401;
        return;
      }
      
      // 2. Check CRUD/FLS
      if(!Schema.sObjectType.Account.isAccessible()) {
        RestContext.response.statusCode = 403;
        return;
      }
    }

14. Q14. How do you document Apex REST APIs?
    Ans: Three documentation methods: 1. Apex comments (for Salesforce devs) 2. Swagger/OpenAPI (external consumers) 3. Postman collection (for testing)
15. Q15. How do you monitor API usage?
    Ans: Tracking approaches: - Custom logging object - Platform Events - Streaming API - Setup → API Usage in Salesforce
16. Q16. Practical Integration Example: Salesforce-to-Salesforce
    Ans: Step-by-Step Process: 1. Create Connected App in both orgs 2. Implement OAuth 2.0 flow to get access token 3. Make callout using token:

    HttpRequest req = new HttpRequest();
    req.setEndpoint('callout:ConnectedAppName/services/data/v56.0/query?q=SELECT+Name+FROM+Account');
    req.setHeader('Authorization', 'Bearer ' + accessToken);
    HttpResponse res = new Http().send(req);

17. Q17. Practical Integration Example: External Payment Gateway
    Ans: Step-by-Step Process: 1. Store credentials in Named Credential 2. Create Apex class for payment processing:

    public class PaymentProcessor {
      public static Boolean chargePayment(Decimal amount, String cardToken) {
        HttpRequest req = new HttpRequest();
        req.setEndpoint('callout:PaymentGateway/api/charge');
        req.setMethod('POST');
        req.setBody(JSON.serialize(new Map{
          'amount' => amount,
          'token' => cardToken
        }));
        
        HttpResponse res = new Http().send(req);
        return res.getStatusCode() == 200;
      }
    }