preflight returns 401 response even though headers correct

Question

I am trying to access a sharepoint server REST api to upload some files. Access is via our tomcat application

Although I believe I setup correctly the headers in IIS the request does not pass the preflight.

Here are the request headers:

Request OPTIONS /_api/contextinfo HTTP/1.1
Accept  */*
Origin  http://localhost:8080
Access-Control-Request-Method   POST
Access-Control-Request-Headers  content-type, accept
Accept-Encoding gzip, deflate
User-Agent  Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; MAAU; rv:11.0) like Gecko
Host    temp-sharepoint
Content-Length  0
Connection  Keep-Alive
Cache-Control   no-cache

and the response headers:

Response    HTTP/1.1 401 Unauthorized
Content-Type    text/plain; charset=utf-8
Server  Microsoft-IIS/7.5
SPRequestGuid   8d690d9d-d06e-101d-6038-8056a7fce7c2
request-id  8d690d9d-d06e-101d-6038-8056a7fce7c2
X-FRAME-OPTIONS SAMEORIGIN
SPRequestDuration   5
SPIisLatency    1
WWW-Authenticate    Negotiate
WWW-Authenticate    NTLM
X-Powered-By    ASP.NET
MicrosoftSharePointTeamServices 15.0.0.4569
X-Content-Type-Options  nosniff
X-MS-InvokeApp  1; RequireReadOnly
Access-Control-Allow-Origin *
Access-Control-Allow-Credentials    true
Access-Control-Allow-Methods    GET,PUT,POST,DELETE,OPTIONS
Access-Control-Allow-Headers    accept,content-type
Date    Fri, 05 Jun 2015 15:52:01 GMT
Content-Length  16

My code to request

var url = sharepointURL + "/_api/contextinfo";
jQuery.ajax({
     url: url,
     type: "POST",
     headers: 
     {
        "Accept": "application/json; odata=verbose"
     },
     xhrFields: {
            withCredentials: true
    },
    crossDomain: true,
     contentType: "application/json;odata=verbose",

Why is not passing the preflight? have I misconfigured the headers?

Answer 1

For a post you will need to add X-RequestDigest: $("#__REQUESTDIGEST").val() in the header.