XMLHTTPRequest为CORS设置适当的标题

Question

I am getting a CORS error when attempting to upload a file. The normal header responses I set up on other pages to get data don't seem to work, I believe I need to properly write the headers in the HTTPRequest but I am not sure how. It should be after I open the request from what I can tell. Here is my my code:

UploadDocument.js

   var fd = new FormData();
   var pro = $("#pro").val(); 

   fileArray[index].submit = true; 

   fd.append("name" + index, "pdf2");
   fd.append("size" + index, fileArray[index].size);
   var fileDate = new Date(fileArray[index].lastModifiedDate);
   var currentDate = new Date();
   fd.append("fileDate" + index, fileDate.getTime());
   fd.append("uploadDate" + index, currentDate.getTime());
   fd.append("officialDate" + index, $('#date').val());
   fd.append("extension" + index, fileArray[index].name.split('.')[1]);
   fd.append("program_id" + index, pro);
   fd.append('file' + index, fileArray[index]);    

   fd.append("length", fileArray.length);
   var request = new XMLHttpRequest();
   request.onreadystatechange = function() {
        if (request.readyState == 4 && request.status == 200) {
            that.prop('disabled', true);
            that.text("Done!");
            that.parent().siblings().children(".deleteBtn").prop("disabled", true); 
        }
     };
   request.open("POST", locationOfServlet, true);
   request.send(fd);

Here is how I handle the headers in the servlet:

RecieveFiles.java

        response.addHeader("Access-Control-Allow-Headers", "Content-Type");
        response.addHeader("Access-Control-Allow-Origin", "*");
        response.addHeader("Access-Control-Allow-Methods", "GET, PUT, POST, OPTIONS, DELETE");
        response.addHeader("Access-Control-Max-Age", "86400");

Answer 1

May be this help you https://developer.mozilla.org/enUS/docs/Web/API/FormData/Using_FormData_Objects

Do you specified "multipart/form-data" attribute in the form?

<form enctype="multipart/form-data">