Analysis of the problem of uploading images with MySQL+SSM+Ajax (picture)

This article mainly introduces the problem of MySQL+SSM+Ajaxuploading images. Has very good reference value. Let’s take a look with the editor below

It was my first time to write the code for uploading images, and I encountered many problems. I worked on it all day yesterday and finally succeeded in the evening. Cheers loudly.

However, after finishing it, there are still many questions that I can’t figure out. So here it can be considered as writing a note. If you forget it in the future, you can review it. It can also be regarded as asking friends from all walks of life. (^_^)

Q.1. It is said on the Internet that Ajax cannot upload files, but there are not many people saying this, and there are still many people sharing files uploaded through Ajax.

I didn't make it through Ajax. In the end, I wrote it through the AjaxSubmit method.

Q.2. Does the AjaxSubmit method have a default limit on the size of file upload? If I choose a file larger than 100KB, it will not be uploaded successfully, but if it is smaller than 100KB, it will be successful.

When uploading more than 100KB, the browser console returns the following prompt. It means that he still executed the success method of ajaxSubmit and returned the value of textStatus as success, but the HTML code content returned by XMLHttpRequest, and errorThrown's responseseText is what I did in spring- Exception handling View web page configured in web.xml.

##js Code (submit form event ):

function postImg(){
 if ($.trim($("#imgFile").val()) == "") { 
   alert("请选择图片！"); 
   return; 
  } 
 console.log($("#imgFile")[0].files[0].size);//小于100*1024，下面的请求就可以成功
 var option = {
  url : '/cloudnote/user/insertUserPhoto.do',
  type : 'POST',
//  dataType : 'json',
  headers : {"ClientCallMode" : "ajax"}, //添加请求头部
  success : function(XMLHttpRequest, textStatus, errorThrown){
   console.log(XMLHttpRequest);
   console.log(textStatus);
   console.log(errorThrown);
   console.log("前端输出上传成功");
   $("#imgClose").click();
  },
  error: function(XMLHttpRequest, textStatus, errorThrown) {
   console.log(XMLHttpRequest);
   console.log(textStatus);
   console.log(errorThrown);
   console.log("前端输出上传失败"); 
  }
 };
 $("#imgForm").ajaxSubmit(option);
 return false; 
}

Front-endHTML form：

<form id="imgForm" > 
　　<p class="modal-content">
 　　<p class="modal-header">
   <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
   <h4 id="修改头像">修改头像</h4>
  </p>
  <p class="modal-body">
  　　<input type="file" id="imgFile" name="imgFile"/> 
   <input id="imgId" name="userId" value="${user.id }" style="display:none" />
  </p>
  <p class="modal-footer">
  　　<button type="button" class="btn btn-default" data-dismiss="modal" id="imgClose">关闭</button>
   <button type="button" class="btn btn-primary" onclick="postImg();" id="imgSubmit">上传</button>
  </p>
 </p>
</form>

The following is the background java code (Controller)

//更新用户头像
 @RequestMapping(value="/insertUserPhoto.do",method = RequestMethod.POST)
 public void insertUserPhoto(
   HttpServletRequest req, HttpServletResponse res){
  System.out.println("----- 插入图片 -------");
  try{
   String id = req.getParameter("userId"); 
   System.out.println(id);
   MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) req;
   MultipartFile file = multipartRequest.getFile("imgFile");
   byte[] photo = file.getBytes();
   boolean result = serv.insertUserPhoto(id, photo); 
   res.setContentType("text/html;charset=utf8"); 
   res.getWriter().write("result:" + result);   
  }catch(Exception e){
   e.printStackTrace();
  }
  System.out.println("----- 插入图片end -------");
 }
 /**
  * 读取用户头像
  * @param req
  * @param res
  */
 @RequestMapping(value="/readPhoto.do", method=RequestMethod.GET)
 public void readPhoto(HttpServletRequest req, HttpServletResponse res){
  System.out.println("------readPohto-----");
  String id = Utils.getSessionUserId(req);
  try {
   User user = serv.selectUserPhoto(id);
   res.setContentType("image/jpeg");
   res.setCharacterEncoding("utf-8"); 
   OutputStream outputStream = res.getOutputStream(); 
   InputStream in = new ByteArrayInputStream(user.getPhoto()); 
   int len = 0; 
   byte[] buf = new byte[1024]; 
   while((len = in.read(buf,0,1024)) != -1){ 
    outputStream.write(buf, 0, len);
   } 
   outputStream.close(); 
  } catch (IOException e) { 
   e.printStackTrace(); 
  } 
  System.out.println("-----readPohto end-----");
  return;
 }

Service implementation class

//查找用户图片（头像）
 public User selectUserPhoto(String id) throws ImageException {
  User user = userDao.findUserById(id);
  if(user == null){
   throw new UserNameException("用户名不存在!");
  }
  Map<String, Object> data = userDao.selectUserPhoto(id);
  System.out.println(data);
  user.setPhoto((byte[]) data.get("photo"));
  return user;
 }
 //更新用户图片（头像）
 public boolean insertUserPhoto(String userId, byte[] photo) throws ImageException, UserNameException {
  if(userId == null || userId.trim().isEmpty()){
   throw new UserNameException("用户id不存在");
  }
  User user = userDao.findUserById(userId);
  if(user == null){
   throw new UserNameException("用户不存在");
  }
  user.setPhoto(photo);
  int n = userDao.updateUserPhoto(user);
  System.out.println("插入图片：" + n);
  return n==1?true:false; 
 }

The photo of the entity class User is of byte[] type;

The photo of the database is longblob:

mapper mapper:

<!-- 更新图片 -->
 <update id="updateUserPhoto" parameterType="cn.tedu.note.entity.User"> 
  UPDATE user set id = #{id}, photo = #{photo,jdbcType=BLOB} <!-- 这里试了，如果不加jdbcType=BLOB 会出错，虽然不是很理解，但也照做了 --> 
  WHERE id = #{id}
 </update> 
 <!-- 获取图片 -->
 <select id="selectUserPhoto" parameterType="String" resultType="Map"> 
   SELECT id as id, photo as photo from user 
   WHERE id=#{id} 
 </select>

Spring-web.xml configuration

 <!-- 文件上传表单的视图解析器 --> 
 <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"> 
  <property name="maxUploadSize"><value>100000</value></property> 
  <property name="defaultEncoding"><value>UTF-8</value></property> 
 </bean>

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