SpringMvc file upload and download

1. First import the jar package:

2. Then, add the upload and download configuration files in applicationContext.xml, as follows:

<!-- 文件上传的配置 -->  
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">     
       <!-- 指定所上传文件的总大小不能超过200KB。注意maxUploadSize属性的限制不是针对单个文件，而是所有文件的容量之和 -->     
       <property name="maxUploadSize" value="200000"/>     
   </bean>     
       
   <!-- 该异常是SpringMVC在检查上传的文件信息时抛出来的，而且此时还没有进入到Controller方法中 -->     
   <bean id="exceptionResolver" class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">     
       <property name="exceptionMappings">     
           <props>     
               <!-- 遇到MaxUploadSizeExceededException异常时，自动跳转到WebContent目录下的error.jsp页面 -->     
               <prop key="org.springframework.web.multipart.MaxUploadSizeExceededException">error</prop>     
           </props>     
       </property>     
   </bean>

3. Okay, the most basic configuration is enough. Next, the jsp page: upload.jsp

1 <form action="upload.do" method="post" enctype="multipart/form-data">
2 文件1: <input type="file" name="myfiles"/><br/>
3 文件2: <input type="file" name="myfiles"/><br/>
4 文件3: <input type="file" name="myfiles"/><br/>
5 <input type="submit" value="上传">
6 </form>

4. Controller The corresponding java code in:

@RequestMapping("/upload.do")  
    public String upload(@RequestParam MultipartFile[] myfiles,HttpServletRequest request) throws IOException {  
        for(MultipartFile file : myfiles){     
            //此处MultipartFile[]表明是多文件,如果是单文件MultipartFile就行了  
            if(file.isEmpty()){   
                System.out.println("文件未上传!");  
            }  
            else{  
                //得到上传的文件名  
                String fileName = file.getOriginalFilename();  
                //得到服务器项目发布运行所在地址  
                String path1 = request.getSession().getServletContext().getRealPath("image")+File.separator;  
                //  此处未使用UUID来生成唯一标识,用日期做为标识  
                String path = path1+ new SimpleDateFormat("yyyyMMddHHmmss").format(new Date())+ fileName;  
                //查看文件上传路径,方便查找  
                System.out.println(path);  
                //把文件上传至path的路径  
                File localFile = new File(path);  
                file.transferTo(localFile);  
                }  
            }  
        return "uploadSuccess";  
    }

This way you can upload the selected pictures on the web page.

The download was successful!

5. File download download.jsp: For testing purposes here, I directly passed the username as a parameter:

a342d74c2459b749c88064982d6b750b下载5db79b134e9f6b82c0b36e0489ee08ed

6. Controller:

@RequestMapping("/download")  
    public String download(String fileName, HttpServletRequest request,  
            HttpServletResponse response) {  
        response.setCharacterEncoding("utf-8");  
        response.setContentType("multipart/form-data");  
        response.setHeader("Content-Disposition", "attachment;fileName="  
                + fileName);  
        try {  
            String path = request.getSession().getServletContext().getRealPath  
                    ("image")+File.separator;  
            InputStream inputStream = new FileInputStream(new File(path  
                    + fileName));  
  
            OutputStream os = response.getOutputStream();  
            byte[] b = new byte[2048];  
            int length;  
            while ((length = inputStream.read(b)) > 0) {  
                os.write(b, 0, length);  
            }  
  
             // 这里主要关闭。              
             os.close();  
  
            inputStream.close();  
        } catch (FileNotFoundException e) {  
            e.printStackTrace();  
        } catch (IOException e) {  
            e.printStackTrace();  
        }  
            //  返回值要注意，要不然就出现下面这句错误！  
            //java+getOutputStream() has already been called for this response  
        return null;  
    }

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