javascript - Download file with ajax() POST request via Spring MVC

Question

I try to download a file. The action is triggered by ajax() POST request. The request sends data in JSON format to the controller. The controller generates the file (bytes) and sends it back.

JavaScript:

function getLicenseFile() {
    $.ajax({
        type: 'POST',
        url: '<%=request.getContextPath()%>/licenses/rest/downloadLicenseFile',
        dataType: 'json',
        contentType: 'application/json;charset=UTF-8',
        data: ko.mapping.toJSON(licenseModel),
        success: function (data) {
            console.log("in sucess")
        },
        error:function (xhr, ajaxOptions, thrownError){
            console.log("in error")
        } 
    });
}  

Controller:

@RequestMapping(value = "/licenses/rest/downloadLicenseFile", method = RequestMethod.POST)
@ResponseStatus(value=HttpStatus.OK)
@ResponseBody
public void createLicenseFile(@Valid @RequestBody License license, HttpServletResponse response) throws Exception {

    logger.debug("Contoller License in: "+ license);

    byte[] licensedata = licenseEncodeDefaultService.createLicenseFile(license);
    logger.debug("licenseData: " + new String(licensedata));

    response.setHeader("Content-Disposition", "attachment; filename="" + license.getCustomer() + ".license"");
    response.getOutputStream().write(licensedata);
    response.flushBuffer();
}

Problem

• The Browser should open a download box, but it does not happen
• The response is handled in the error: section of ajax function (but the HTTP Status is OK)

So what do I do wrong or what is the proper way to do this?

Answer 1

Just send a URL of file in response and then "visit" it in your success callback.

function getLicenseFile() {
    $.ajax({
        type: 'POST',
        url: '<%=request.getContextPath()%>/licenses/rest/downloadLicenseFile',
        dataType: 'json',
        contentType: 'application/json;charset=UTF-8',
        data: ko.mapping.toJSON(licenseModel),
        success: function (data) {
            window.open(data.fileUrl);
            // or window.location.href = data.fileUrl;
        },
        error:function (xhr, ajaxOptions, thrownError) {
            console.log("in error");
        } 
    });
}

data.fileUrl should be set in response by server to say client where to get the file.

So your server will send a response with JSON like

{
    "fileUrl": "http://mysite.com/files/0123456789"
}