Spring MVC realizes the upload and download of files
In SpringMVC, the upload of files is achieved through MultipartResolver. So, if you want to upload files, just register the corresponding MultipartResolver in spring-mvc.xml.
There are two implementation classes for MultipartResolver:
CommonsMultipartResolver
StandardServletMultipartResolver
The difference between the two:
The first requires jar package support such as Apache's commons-fileupload, but it can be used in older versions of servlet.
The second one, which does not require third-party jar package support, uses servlet's built-in upload function, but can only be used in versions above Servlet 3.
The first step to use:
/ two packages used for CommonsMultipartResolver upload /
"commons-fileupload:commons-fileupload:1.3.1"
"commons-io:commons-io:2.4"
If it is a maven project, import it directly:
Commons-fileupload
Commons-fileupload
1.3.1
Dispatcher-servlet.xml configuration:
Web.xml:
Dispatcher org.springframework.web.servlet.DispatcherServlet contextConfigLocation classpath:dispatcher-servlet.xml dispatcher /
Backend java (upload and download) processing code:
Package edu.nf.ch08.controller
Import org.apache.commons.io.FileUtils
Import org.springframework.http.HttpHeaders
Import org.springframework.http.HttpStatus
Import org.springframework.http.MediaType
Import org.springframework.http.ResponseEntity
Import org.springframework.stereotype.Controller
Import org.springframework.web.bind.annotation.GetMapping
Import org.springframework.web.bind.annotation.PostMapping
Import org.springframework.web.multipart.MultipartFile
Import org.springframework.web.servlet.ModelAndView
Import java.io.File
Import java.io.IOException
/ * *
@ author wangl
@ date 2018 Universe 11 Universe /
@ Controllerbr/ > * /
@ Controller
/ * *
To upload a file, you only need to pass in a MultipartFile object by Spring, which can obtain the information about the file upload. A MultipartFile means that a single file is uploaded, and when you need to upload multiple files, you only need to declare it as an MultipartFile [] array. @ return*/
@ PostMapping ("/ upload") br/ > * /
@ PostMapping ("/ upload")
/ / get the current system user directory
String home = System.getProperty ("user.home")
/ / specify the uploaded folder directory
File uploadDir = new File (home + "/ files")
/ / if the directory does not exist, create
If (! uploadDir.exists ()) {
UploadDir.mkdir ()
}
/ / get the name of the uploaded file
String fileName = file.getOriginalFilename ()
/ / build a complete file upload object
File uploadFile = new File (uploadDir.getAbsolutePath () + "/" + fileName)
Try {
/ / upload via transferTo method
File.transferTo (uploadFile)
} catch (IOException e) {
E.printStackTrace ()
Throw new RuntimeException (e.getMessage ())
}
/ / Save the file name into Model and forward it to the index page
ModelAndView mv = new ModelAndView ("index")
Mv.addObject ("fileName", fileName)
Return mv
}
/ * *
The file download reads the server local file and encapsulates it as a ResponseEntity object response client, writing back an array of bytes @ param fileName file name @ return*/
@ GetMapping ("/ download") br/ > * /
@ GetMapping ("/ download")
/ / build a local file path based on the file name
String filePath = System.getProperty ("user.home") + "/ files/" + fileName
/ / build File objects based on the file path
File file = new File (filePath)
/ / create a response header object and set the response information
HttpHeaders headers = new HttpHeaders ()
Try {
/ / A pair of file names are re-encoded to prevent Chinese garbled in the response header
String headerFileName = new String (fileName.getBytes ("UTF-8"), "ISO-8859-1")
/ / set the response content to be handled as an attachment and specify a file name
Headers.setContentDispositionFormData ("attachment", headerFileName)
/ / set the response header type to application/octet-stream, which means it is a stream type
Headers.setContentType (MediaType.APPLICATION_OCTET_STREAM)
/ / convert the file to a byte array
Byte [] bytes = FileUtils.readFileToByteArray (file)
/ / create ResponseEntity object (encapsulate file byte array, response header, response status code)
ResponseEntity entity = new ResponseEntity (bytes, headers, HttpStatus.CREATED)
/ / finally, the entire ResponseEntity object is returned to DispatcherServlet
Return entity
} catch (Exception e) {
E.printStackTrace ()
Throw new RuntimeException ("File download failed")
}
}
}
The web page where the file is uploaded is html:
Title
File upload
File:
Jsp (download file) page forwarded after a successful upload:
Title
${fileName}
Project structure:
