In an internal SFDC Http Get from a VF Page, how do I authenticate for the redirected URL?

Question

I'm trying to execute an internal http: GET from a VF page on a Knowledge Article so that I can parse the response HTML for some text in the page. (The Knowledge article looks like this: https://cs7.salesforce.com/articles/FAQ/Test-Article-1)

So my problem is that if I do an http GET on the Original VisualForce URL: 'https://c.cs7.visual.force.com/articles/FAQ/Test-Article-1' then I will be redirected to: 'https://cs7.salesforce.com/articles/FAQ/Test-Article-1'

However, if I do an http GET on the second URL, I am returned with the Salesforce login page. Apparently, my sessionId isn't valid there. How can I retrieve the body of the second URL while I'm authenticated within visualforce?

Thanks for any help, DaveS

Here's my code:

public String getResponseBody(String originalUrl) {
    originalUrl ='https://c.cs7.visual.force.com/articles/FAQ/Test-Article-1';
    Boolean redirect = false;
    Http h = new Http();
    HttpRequest req = new HttpRequest();
    req.setEndpoint(originalUrl);
    req.setMethod('GET');
    req.setHeader('Authorization','Bearer '+UserInfo.getSessionId());
    req.setHeader('Cookie','sid='+UserInfo.getSessionId());  // Not sure this is necessary

    HttpResponse res = h.send(req);

    //Redirection checking
    if(res.getStatusCode() >=300 && res.getStatusCode() <= 307 && res.getStatusCode() != 306) {
        do {
            redirect = false; // reset the value each time
            String loc = res.getHeader('Location'); // get location of the redirect
            if(loc == null) {
                redirect = false;
                break;
            }
            req = new HttpRequest();
            req.setEndpoint(loc);
            req.setMethod('GET');
            req.setHeader('Authorization','Bearer '+UserInfo.getSessionId());
            req.setHeader('Cookie','sid='+UserInfo.getSessionId());
            res = h.send(req);
            if(res.getStatusCode() != 500) { // 500 = fail
                if(res.getStatusCode() >=300 && res.getStatusCode() <= 307 && res.getStatusCode() != 306) {
                    redirect= true;
                }
            }
        } while (redirect && Limits.getCallouts() != Limits.getLimitCallouts());
    }
    //congratulations you're outside of the redirects now

    return res.getBody();
}

Answer 1

I finally figured it out. When you're in Visualforce, your domain will always be something like c.cs7.visualforce.com. However, other salesforce pages such as standard pages will be delivered by cs7.salesforce.com Your session Id from within c.cs7.visualforce.com will NOT work within cs7.salesforce.com So to execute an HTTP get on a resource in the alternate domain, you have to authenticate with that new domain. This can be done in one of 2 ways:

1. Load either the Enterprise or Partner WSDL back into Salesforce and use the "Login" API call.
2. Since you're only using one API call, it might be adequate to just create your own XML Soap message for the login. You should be able to easily search the response Body for the session Id.

Once you have the session Id, execute a single http GET to the corresponding domain and you won't be redirected.