Unable to download Metadata WSDL from Org

Question

Related to this other question Discover Schema of Source + Metadata XML formats I am trying to download the Metadata API WSDL file from the Orgs URL https://ServInstance.salesforce.com/services/wsdl/metadata using this simple Apex code:

public Dom.Document mdApiWsdl() {
    HttpRequest request = new HttpRequest();
    request.setEndpoint(URL.getOrgDomainUrl().toExternalForm() + '/services/wsdl/metadata');
    request.setMethod('GET');
    request.setHeader('Authorization', 'OAuth ' + UserInfo.getSessionId());
    request.setHeader('Content-Type', 'application/xml');

    HttpResponse response = new Http().send(reqquest);
    return response.getBodyDocument();
}

The issue I face is that the page is not a WSDL XML document but a strange HTML page simulating it. In a browser, it's possible to download the file as XML but in Apex code I couldn't find a way.

Why is Salesforce preventing us from downloading this single WSDL?

Answer 1

The particular page is expecting a sid session cookie rather than an Authorization header. You'll need a full UI session and then pass that session id into the Cookie header.

E.g.

HttpRequest request = new HttpRequest();
request.setEndpoint(URL.getOrgDomainUrl().toExternalForm() + '/services/wsdl/metadata');
request.setMethod('GET');
//request.setHeader('Authorization', 'OAuth ' + UserInfo.getSessionId());
request.setHeader('Cookie','sid='+UserInfo.getSessionId());
request.setHeader('Content-Type', 'application/xml');

HttpResponse response = new Http().send(request);
System.debug(response.getBody());