Using HttpServletResponse for download functions

The download function can also be implemented in JS, but this approach exposes the file address to an external surface and is unsafe.

We generally recommend the use of the background method for download. The SPRING-MVC architecture is used in the project, in which the controller is one of the Servlets, and the httpservletresponse can be used to set the response header information like a servlet to achieve the download function.

first, the use of httpservletresponse to achieve the download function

1. Gets the absolute path of the file to download
2. Get the file name to download
3. Set the Content-disposition response header to control the browser download form to open the file
4. Get the file input stream to download
5. Creating a data buffer
6. Getting OutputStream streams from response objects
7. Writes the FileInputStream stream to buffer buffers
8. Using OutputStream to output buffer data to the client browser

second, the use of httpservletresponse to realize the download function considerations

1. It is recommended to use OutputStream stream when writing file download function, avoid using printwriter stream, because OutputStream stream is byte stream, can handle any kind of data, and PrintWriter stream is character stream, can only handle character data, Processing byte data with a character stream can result in data loss.

2. When downloading the Chinese file, it is important to note that the Chinese file name is encoded using the Urlencoder.encode method (Urlencoder.encode (filename, "character encoding")), otherwise the file name will be garbled.

   Response.setheader ("Content-disposition", "attachment;filename=" +urlencoder.encode (filename, "UTF-8"));

Third, httpservletresponse implementation of the downloaded source code (SPRING-MVC Controller)

1 /**2 * Download images from the server to the client locally according to FilePath3    */4@RequestMapping ("/downloadjpg")5  Public voidDownloadjpg (@RequestParam (value= "FileId") String fileid,httpservletresponse response) {6Jcyappealdatum datum=Jcyappealdatumservice.get (fileId);7     if(datum!=NULL) {8File file=NewFile (Datum.getfilepath ());9         if(File.exists ()) {TenInputStream istream=NULL; One             Try { AIStream =Newfileinputstream (file); -                 byte[] buffer =New byte[Istream.available ()]; - istream.read (buffer); theString fileName = datum.getfilename () + ". jpg"; -Response.setcontenttype ("Image/jpeg");//formatting returned content -                 //set to return the corresponding header content, the Chinese name must be transcoded ( -String exportname = "Attachment;filename=" +NewString ((fileName). GetBytes ("gb2312"), "Iso8859-1"); +Response.setheader ("Content-disposition", exportname); - Response.getoutputstream (). write (buffer); +}Catch(Exception e) { A e.printstacktrace (); at}finally { -                 Try { - istream.close (); -}Catch(Exception E2) { - e2.printstacktrace (); -                 }     in             } -     } to              +     } -}

Iv. several common contenttype

Serial number	Content Type	File name extension	Describe
1	Application/msword	Doc	Microsoft Word
2	Application/octet-stream bin	DMS LHA LZH EXE class	Executable program
3	Application/pdf	Pdf	Adobe Acrobat
4	Application/postscript	AI EPS PS	PostScript
5	Appication/powerpoint	Ppt	Microsoft Powerpoint
6	Appication/rtf	Rtf	RTF format
7	Appication/x-compress	Z	UNIX Compressed Files
8	Application/x-gzip	Gz	Gzip
9	Application/x-gtar	Gtar	Tar document (GNU format)
10	Application/x-shockwave-flash	Swf	MacroMedia Flash
11	Application/x-tar	Tar	Tar (4.3BSD)
12	Application/zip	Zip	WinZip
13	Audio/basic	Au snd	Sun/next sound files
14	Audio/mpeg	MPEG MP2	Mpeg sound files
15	Audio/x-aiff	Mid MIDI RMF	Midi format
16	Audio/x-pn-realaudio	Ram RA	Real Audio Sound
17	Audio/x-pn-realaudio-plugin	Rpm	Real Audio Plugin
18	Audio/x-wav	Wav	Microsoft Windows Sound
19	Image/cgm	Cgm	Computer graphics meta-file
20	Image/gif	Gif	COMPUSERVE GIF Image
21st	Image/jpeg	JPEG jpg JPE	JPEG image
22	Image/png	Png	PNG Images

　　

Using HttpServletResponse for download functions