title: Getting request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource
body: <p>I am trying to send an Ajax request to a Tomcat server from my application, but I am getting this error (my web app is running on Chrome):</p>
  
  <blockquote>
    <p>Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access. The response had HTTP status code 403.</p>
  </blockquote>
  
  <p>I have tried using</p>
  
  <pre><code>'Access-Control-Allow-Origin' : 'http://localhost:8080/app',
  </code></pre>
  
  <p>but it didn't work.</p>
  
  <p>My Ajax code:</p>
  
  <pre><code> var arr = [1];
     $.ajax({ 
     url: 'http://localhost:8080/app',
     type: 'POST',
     contentType:'application/json',
     headers: {
     'Access-Control-Allow-Origin' : 'http://localhost:8080',
     },
         data: JSON.stringify(arr[0]),
         success: function(data){
          //On ajax success do this
               alert(data);
            }
       });
  </code></pre>