问jquery getJSON文件上传？

EN

<form name="employment" id="employment" enctype="multipart/form-data">
  <div id="contactform">
    <div class="information">
      <label>Full Name: *</label>
      <input type="text" name="name" id="name" class="inputbox required" />
    </div>
    <div class="information">
      <label>Email Address: *</label>
      <input type="text" name="email" id="email" class="inputbox required email" />
    </div>
    <div class="information">
      <label>Contact Number: *</label>
      <input type="text" name="number" id="number" class="inputbox required" />
    </div>
    <div class="information">
      <label>Position: *</label>
      <select name="position" id="position" class="inputbox required">
        <option value="">- Please Select-</option>
        <?php foreach($this->Positions as $position) { ?>
        <option value="<?php echo $position->name; ?>"><?php echo $position->name; ?></option>
        <?php }; ?>
        <option value="Traineeship">Traineeship</option>
        <option value="Clerkship">Clerkship</option>
      </select>
    </div>
    <div class="information">
      <label>Cover Letter:</label>
      <textarea name="letter" id="letter" class="inputbox"></textarea>
    </div>
    <div class="information">
      <label>Please upload your resum&eacute; in PDF or Word format (less than 2MB)*:</label>
      <input type="file" name="resume" id="resume" class="inputbox" />
    </div>
    <input type="submit" name="submit" id="submit" value="Submit" class="submitButton" />
  </div>
  <div class="clear"></div>
  </div>
</form>

$("#employment").validate({              
    submitHandler: function(form) { 
      var name  = $("#name").val();
      var email     = $("#email").val();
      var number    = $("#number").val();
      var position  = $("#position").val();
      var letter    = $("#letter").val();
      var resume    = $("#resume").val();

      $.getJSON("/index.php?option=com_json&format=raw", { task: "employment", e_name: name, e_email: email, e_number: number, e_position: position, e_letter: letter, e_resume: resume }, function(data) {
        var response = eval(data);
        if (response["result"] == 1) {
          $("form#employment").hide();
          $("#loading").empty();
          $("#loading").append("<strong>Thank you for submitting your resume.</strong>");
        } else if (response["result"] == 3) {
          alert("There has been an error, please try again.");
          $("#loading").empty();
          $("form#employment").show();
        } else {
          alert("There has been an error, please try again.");
          $("#loading").empty();
          $("form#employment").show();
        };
      });
    }
  });