ajaxFileUpload上传图片预览总结

      背景：我们平时在做项目的时候，肯定会遇到上传头像、图片、文件等异步上传的功能，今天就以ajaxFileupload组件上传头像为例总结一下该组件的用法。

      Tips:  我在以前的博客中分享过三种上传组件，其实主要代码已经在这篇文章体现了，今天再次总结一下ajaxfileupload这个组件，发现在高版本(1.9以上)的Jquery下ajaxfileupload提示异常，然后我就把ajaxfileupload的jQuery对象都替换成了$就可使用了，对于ajaxFileUpload 报这错jQuery.handleError is not a function，请猛戳   这里，对就是这里。附件是修改好可使用的ajaxfileupload.js文件。

     需求：自定义样式【上传】按钮，点击之后【上传】按钮，打开文件选择对话框，选择文件后自动上传，并可预览该图片。

     分析：

     1.【上传】按钮是a链接，但是上传文件必然需要一个input type="file"的元素，在点击a链接这个【上传】按钮的时候，触发input type="file"元素的click方法打开文件选择对话框，选择文件后，触发input type="file" 的onchange方法，然后调用ajaxfileupload的上传方法开始上传。

       用到的技术：jquery,ajaxfileupload,springMVC

    代码：

    1.HTML片段

<div class="uploadPicture">
       <img id="imgHead" src="" width="106" height="122" alt="头像"> 
       <input type="file" onchange="uploadHead();" id="basicInfoHead" style="display:none;"
        name="basicInfoHead" />
      <input type="hidden" id="basicHeadUrl" >
       <a href="#basicInfo" id="uploadBasicInfoHead" >上传头像</a>
      </div>

  2.JS代码

//上传头像，触发click方法
    $('#uploadBasicInfoHead').on('click',function(){
     $('#basicInfoHead').click();
    });

function uploadHead(){
  $.ajaxFileUpload({
      url:"${pageContext.request.contextPath}/profile/uploadBasicHead",//需要链接到服务器地址 
      secureuri:false,
      fileElementId:"basicInfoHead",//文件选择框的id属性
      dataType: 'json',   //json
      success: function (data) {
         $("#imgHead").attr("src","${pageContext.request.contextPath}/profile/readImage?imagePath="+data.imagePath);
        $('#basicHeadUrl').val(data.imagePath);
      },error:function(XMLHttpRequest, textStatus, errorThrown){
     alert('上传失败！');
   }
  });
};

  3.JAVA代码

//上传文件方法
@RequestMapping(value = "profile/uploadBasicHead", produces = "text/plain;charset=UTF-8")
 @ResponseBody
 public String ajaxUpload(HttpServletRequest request) throws IllegalStateException,
   IOException {
  MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
  String fileName = "";
  String uploadPath = "uploadFile/head/";
  String path =request.getSession().getServletContext().getRealPath("/")+uploadPath;  
  /*File uploadPathFile = new File(path);
  if (!uploadPathFile.exists()) {  
   uploadPathFile.mkdir();  
     }*/
  String realPath = "";
  for (Iterator it = multipartRequest.getFileNames(); it.hasNext();) {
   String key = (String) it.next();
   MultipartFile mulfile = multipartRequest.getFile(key);
   fileName = mulfile.getOriginalFilename();
   fileName = handlerFileName(fileName);
   File file = new File(path + retFileName);
   mulfile.transferTo(file);
  }
   realPath = "{\"imagePath\":\""+uploadPath+fileName+"\"}";
  return realPath;
 }

//文件名称处理
private String handlerFileName(String fileName) {
  //处理名称start
  fileName = (new Date()).getTime()+"_"+fileName;
//时间戳+文件名，防止覆盖重名文件
  String pre = StringUtils.substringBeforeLast(fileName, ".");
  String end = StringUtils.substringAfterLast(fileName, ".");
  fileName = Digests.encodeByMd5(pre)+"."+end;//用MD5编码文件名，解析附件名称
  //处理名称end
  return fileName;
 }

//预览，获取图片流
@RequestMapping(value = "profile/readImage", produces = "text/plain;charset=UTF-8")
    public void readImage(HttpServletRequest request, HttpServletResponse response){
     String imagePath = request.getSession().getServletContext().getRealPath("/")+request.getParameter("imagePath");
     try{
      File file = new File(imagePath);
         if (file.exists()) {
           DataOutputStream temps = new DataOutputStream(response
             .getOutputStream());
           DataInputStream in = new DataInputStream(
             new FileInputStream(imagePath));
           byte[] b = new byte[2048];
           while ((in.read(b)) != -1) {
     temps.write(b);
     temps.flush();
           }
           in.close();
           temps.close();
         } 
       } catch (Exception e) {
        e.printStackTrace();
       }
    }