javaweb文件上传

<div id="image-holder" style="margin:0 auto;width:200px;height:250px;border:1px solid gray">

    <img src="" style="width:100%;height:100%">

    </div> 

<input style="margin:0 auto;" type="file" id="id_pic_upload" name="name_pic">

<button type="button" class="btn btn-primary" id="id_ok_upload">上传</button>

//上传图片预览

$("#id_pic_upload").on('change', function () {

  if (typeof (FileReader) != "undefined") {   

  var reader = new FileReader();

  reader.onload = function(e){

  $("#image-holder img").attr("src",e.target.result);

  }

    reader.readAsDataURL($(this)[0].files[0]);

  } else {

    Tools_ShowMsg("设备不支持预览，可尝试升级");

  }

//ajax上传

//id_ok_upload 任意按钮

$("#id_ok_upload").click(function(){

var formData = new FormData();

    formData.append('name_pic', $('#id_pic_upload')[0].files[0]);   //name_pic 为后台接收名称，id_pic_upload为file类型input

    $.ajax({

    url:"servlet/FileServlet",

    type:"post",

    cache:false,

    data:formData,

    processData:false,

    contentType:false,

    success:function(data)

    {

    console.log("success");

    },

    error:function(err)

    {

    console.log("error");

    }

    });

});

//jsp

<form action="uploadservlet" method="post" enctype="multipart/form-data">

    <input type="file" name="pic">

    <input type="submit" name="submit">

    </form>

//servlet

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

response.setContentType("text/html");

request.setCharacterEncoding("utf-8");

response.setCharacterEncoding("utf-8");

if(ServletFileUpload.isMultipartContent(request))

{

FileItemFactory factory = new DiskFileItemFactory();

ServletFileUpload upload = new ServletFileUpload(factory);

try {

List<FileItem> items = upload.parseRequest(request);

Iterator<FileItem> it = items.iterator();

while(it.hasNext())

{

FileItem item = it.next();

if(item.isFormField())

{

}else

{

if(item.getFieldName().equals("pic"))

{

String fileName = item.getName();

String path = request.getSession().getServletContext().getRealPath("upload");

File file = new File(path,fileName);

item.write(file);

System.out.println(fileName + " 上传成功");

}

}

}

} catch (FileUploadException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}