How to download file from server using jQuery AJAX and Spring MVC 3

Question

I want to implement downloading (with AJAX) of uploaded file from server. On the server side I wrote the code

@RequestMapping(value = "/getInvoice/approvalId/{approvalId}", method = RequestMethod.GET)
public
@ResponseBody
byte[] getInvoice(@PathVariable("approvalId") Integer approvalId, HttpServletResponse response) throws IOException {
    String fileName = this.approvalService.getFullInvoicePath(approvalId);
    File file = new File(fileName);

    response.setContentType("application/octet-stream");
    response.setHeader("Content-Disposition", "attachment; filename="" + file.getName() + """);
    response.setHeader("Pragma", "no-cache");
    response.setHeader("Cache-Control", "no-cache");
    response.setContentLength((int) file.length());
    return FileUtils.readFileToByteArray(file);
}

Fiddler2 shows response:

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Content-Disposition: attachment; filename="invoice.pdf"
Pragma: no-cache
Cache-Control: no-cache
Content-Type: application/octet-stream;charset=UTF-8
Content-Length: 1028351
Date: Sun, 17 Jul 2011 08:16:41 GMT

%PDF-1.4
%????
6 0 obj <</Linearized 1/L 1028351/O 8/E 1024254/N 1/T 1028185/H [ 5056 544]>>
endobj

xref
6 238 
*** FIDDLER: RawDisplay truncated at 128 characters. Right-click to disable truncation. ***

How to handle and force browser to download file using jQuery?

Answer 1

Two options are usually used but neither involves AJAX. And jQuery won't be a great help either.

Option 1: IFrame

Place an invisible IFrame into your page:

<iframe id="downloadFrame" style="display:none"></iframe>

When the download should start (you didn't mention how it is triggered), use Javascript (and possibly jQuery) to set the URL for the IFrame, which is something like /getInvoice/approvalId/123 in your case:

var iframe = document.getElementById("downloadFrame");
iframe .src = "/getInvoice/approvalId/123";

Setting the IFrame URL should trigger the browser to present the download dialog.

Option 2: Navigate to the download URL

The second option is even simpler. Just navigate to the download URL. Once the browser figures out it's a MIME type that cannot be displayed, it will present a download dialog.

So when the download is triggered, execute the following JavaScript code:

window.location.href = "/getInvoice/approvalId/123";

---

Note

I'm not sure if all browser will reliably present a download dialog with PDF files. Some browsers might try to display it within the browser itself. The Content-Disposition HTTP header is helpful but no guarantee.