springMVC+ajax实现文件上传且带进度条实例

<form id= "uploadform"> 
   <p >指定文件名： <input type="text" name="filename" value= ""/></p > 
   <p >上传文件： <input type="file" name="file"/></ p> 
   <input type="button" value="上传" onclick="doupload()" /> 
</form> 

function doupload() { 
   var formdata = new formdata($( "#uploadform" )[0]); 
   $.ajax({ 
     url: 'http://localhost:8080/xiaochangwei/file/upload' , 
     type: 'post', 
     data: formdata, 
     async: false, 
     cache: false, 
     contenttype: false, 
     processdata: false, 
     success: function (returndata) { 
       alert(returndata); 
     }, 
     error: function (returndata) { 
       alert(returndata); 
     } 
   }); 
}

@requestmapping(value = "/upload", method = requestmethod.post)
  public string upload(httpservletrequest request, @requestparam("file") multipartfile file, modelmap model) {
    system.out.println("开始");
    string path = request.getsession().getservletcontext().getrealpath("upload");
    string filename = file.getoriginalfilename();
    // string filename = new date().gettime()+".jpg";
    system.out.println(path);
    file targetfile = new file(path, filename);
    if (!targetfile.exists()) {
      targetfile.mkdirs();
    }

    // 保存
    try {
      file.transferto(targetfile);
    } catch (exception e) {
      e.printstacktrace();
    }
    model.addattribute("fileurl", request.getcontextpath() + "/upload/" + filename);
    return "result";
  }

<script type="text/javascript">

    function upladfile() {
      var fileobj = document.getelementbyid("file").files[0]; // js 获取文件对象
      var filecontroller = "http://localhost:8080/xiaochangwei/file/upload";          // 接收上传文件的后台地址 

      // formdata 对象
      var form = new formdata($( "#uploadform" )[0]);

      // xmlhttprequest 对象
      var xhr = new xmlhttprequest();
      xhr.open("post", filecontroller, true);
      xhr.onload = function () {
        // alert("上传完成!");
      };

      xhr.upload.addeventlistener("progress", progressfunction, false);
      xhr.send(form);
    }

    function progressfunction(evt) {
      var progressbar = document.getelementbyid("progressbar");
      var percentagediv = document.getelementbyid("percentage");
      if (evt.lengthcomputable) {
        progressbar.max = evt.total;
        progressbar.value = evt.loaded;
        percentagediv.innerhtml = math.round(evt.loaded / evt.total * 100) + "%";
        if(evt.loaded==evt.total){
          alert("上传完成100%");
        }
      }
    } 

  </script>
  

  <progress id="progressbar" value="0" max="100"></progress>


<form id= "uploadform">

  <input type="file" id="file" name="myfile" />
  <input type="button" onclick="upladfile()" value="上传" />

</form>