File uploading and downloading in SSM

                                        File upload and download （maven project ）

Prerequisite: import dependency

<dependency>
	<groupId>commons-fileupload</groupId>
	<artifactId>commons-fileupload</artifactId>
	<version>1.3.2</version>
</dependency>

And then in springmvc.xml File （ The specific attribute is Baidu itself ---- I don't know , Hey ）

<!-- add to multipartResolver Of bean Support file upload  -->
<bean id="multipartResolver"
class="org.springframework.web.multipart.commons.CommonsMultipartResolver" p:maxUploadSize="802400" p:defaultEncoding="utf-8"/> 

One 、 Upload of files

stay controller Steps for uploading in ：

1. Get the file name ：String fname = pic.getOriginalFilename();
2. Process file names （ The file name stored in the database is a random file name ）：

3.  Steps to generate random names ：
   a. Get the suffix of the file 
   String ext = FilenameUtils.getExtension(fname);
   b. Generate random file names 
   String randomName = UUID.randomUUID()+"."+ext;

    

4.   Specify the physical path of the uploaded file （imgs For the generated folder ）：String zPath = req.getServletContext().getRealPath("imgs");
5. structure file object , Upload

6.  Splice paths ：
   File file = new File(zPath+'/'+randomName);
   FileUtils.copyInputStreamToFile(pic.getInputStream(), file);
   String savePath = zPath+'/'+randomName;
   stu.setPicPath(savePath);

    

Precautions for file uploading ：

1. In the form containing the file upload form Add to label enctype="multipart/form-data".
2. Uploaded on file input In the tag type Attribute file, and name Define your own , Then the backstage is controller Need to use . 
3. stay controller Must be by MultipartFile pic This attribute ,pic Corresponding name attribute

Two 、 Download files

Specify the file to download ：<a href="download.do?fileName=logo.jpg"> Click to download </a>

stay controller Steps for file download in ：

1. Get the file ：String fName = req.getServletContext().getRealPath("/imgs/"+fileName);
2. Build an input stream from a file ：FileInputStream fis = new FileInputStream(fName);
3. Building a cache ：byte[] by = new byte[fis.available()]; Among them fis.available() Means to create a just right cache , modest , It is just fine
4. This is optional == Prevent Chinese file names ： The default Chinese operating system is GBK, The default character encoding format interpreted by the browser is ISO-8859-1
           fileName = new String(fileName.getBytes("GBK"),"ISO-8859-1");
5. Set the corresponding header file and related contents ：

resq.setHeader("content-disposition", "attachment;filename="+fileName);
resq.setContentType("application/octet-stream");
resq.setContentLength(fis.available());

Finally, perform read / write and close operations

 Reading and writing 
fis.read(by);// read 
resq.getOutputStream().write(by);// Write 
resq.getOutputStream().flush();// Refresh 
resq.getOutputStream().close();// close 
fis.close();

This is based on ssm The file upload and download of have been completed