Connection between Salesforce with external system using REST API?

Question

I need to connect Salesforce with external system using REST API. I am connecting Salesforce with external system using Username and password.

While connecting I get error code : 302

I have attached my code.

I read the documentation but couldn't get any idea to connect this.

Code:

    public class AuthCallout {

        public void basicAuthCallout(){
        HttpRequest req = new HttpRequest();
        req.setHeader('Authorization','OAuth ');
        req.setHeader('Accept-Encoding','gzip,deflate');
        req.setHeader('Content-Type','application/json');
        //req.setMethod('GET');
        req.setEndpoint('https://api.xero.com/api.xro/2.0/');
        req.setMethod('GET');

        // Specify the required user name and password to access the endpoint 

        // As well as the header and header information 


         String username = 'xxxxxxx';
         String password = '@@@@@@@@@@';

         Blob headerValue = Blob.valueOf(username + ':' + password);
         String authorizationHeader = 'BASIC ' +
         EncodingUtil.base64Encode(headerValue);
         //req.setHeader('Authorization', authorizationHeader);

         // Create a new http object to send the request object 

         // A response object is generated as a result of the request   


         Http http = new Http();
         try {
           HTTPResponse res = http.send(req);
           System.debug('Xero'+res.getBody());
         }
         Catch(Exception Ex) {
           System.Debug(Ex.getmessage());
         }
    }
}

Answer 1

Based on the Xero API documentation (http://developer.xero.com/documentation/api/api-overview/) they mandate authentication using OAuth (v1.0a).

In your sample code you are using BASIC authentication which will not correctly authenticate you and therefore redirect you to a different page.

Please read up on completing an OAuth (v1.0) authentication flow. Here are some great resources to start with:

1. Salesforce OAuth 1.0 Authentication Flow - https://help.salesforce.com/HTViewHelpDoc?id=remoteaccess_oauth_1_flows.htm&language=en_US
2. Sundog Interactive walkthrough of completing OAuth using APEX - https://www.sundoginteractive.com/sunblog/posts/using-oauth-1.0-in-salesforce-apex
3. Another StackExchange question to help further - Using OAuth 1.0 encoded requests for external webservice calls

Hopefully this gets you going in the right direction.

Answer 2

A 302 error is a redirect (as you may already know). Is it possible that the Http request is malformed and the endpoint is redirecting to an auth required page? You can use a site like: http://requestb.in/ to help debug http requests.