input type file goes blank when submit form onchange

Question

Hi i am uploading a file using <input type="file"> in spring mvc. I submit form on change event of file and show uploaded process. But file content not uploaded and get null on server. If i upload on click of submit button every thing works fine. This is my code:

Html File:

<form:form method="POST" modelAttribute="book" id="saveBook"
   name="saveBook" enctype="multipart/form-data">
   <table width="100%" border="0" cellspacing="0" cellpadding="0">
      <tr>
         <td>Book :</td>
         <td>&nbsp;</td>
         <td>
            <input type="file" name="file" id="file" class="edit_form" onchange="return upload('<c:url value='/bookstore/librery/uploadBook' />', 'saveBook', this);" />
            &nbsp; 
            <form:errors path="file" />
         </td>
      </tr>
   </table>
</form:form>

Jquery Code:

function upload(requestUrl, formId, clickedObj) {

    if (clickedObj && eval(clickedObj) && clickedObj != null && clickedObj != undefined) {
        clickedObj.disabled = true;
    }

    var formData = new FormData(document.getElementById(formId));
    $.ajax({
        'url': requestUrl,
        'type': 'POST',
        'data': formData,
        'cache': false,
        'contentType': false,
        'processData': false,
        success: function (data) {
            $("#tempLoc").val(data.tempLoc);
            $("#bookPreview").attr("src", "data:image/png;base64," + data.image);
            $("#image").val(data.image);

            clickedObj.disabled = false;
        },
        error: function (xhr, status, err) {
            clickedObj.disabled = false;

            var tempErrorHTML = getAjaxRequestErrorMsg(xhr);
            alert(tempErrorHTML);
        },
        xhr: function () {
            var xhr = new window.XMLHttpRequest();
            xhr.upload.addEventListener("progress", function (evt) {
                if (evt.lengthComputable) {
                    var percentComplete = (evt.loaded / evt.total) * 100;
                    //Do something with upload progress
                    alert('percentComplete = ' + percentComplete + '%');
                }
            }, false);
            return xhr;
        },
    }, 'json');

}

If i call upload function on click of submit button every thing works fine. I think form is submitted before file uploaded but don't know how to make things correct.

I can't use submit function because I need to show upload progressbar. Please help.

Thanks In Advance.