Downloading a file from spring controllers

Question

I have a requirement where I need to download a PDF from the website  The PDF needs to be generated within the code  which I thought would be a combination of freemarker and a PDF generation framework like iText  Any better way    However  my main problem is how do I allow the user to download a file through a Spring Controller

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In my case I m generating some file on demand  so also url has to be generated   For me works something like that    RequestMapping value     files  filename       method   RequestMethod GET  produces    text csv    ResponseBody public FileSystemResource getFile  PathVariable String filename        String path   dataProvider getFullPath filename       return new FileSystemResource new File path        Very important is mime type in produces and also that  that name of the file is a part of the link so you has to use  PathVariable   HTML code looks like that    lt a th href      dbreport files   file name     gt Download lt  a gt    Where   file name  is generated by Thymeleaf in controller and is i e   result 20200225 csv  so that whole url behing link is  example com aplication dbreport files result 20200225 csv   After clicking on link browser asks me what to do with file - save or open

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With Spring 3 0 you can use the HttpEntity return object  If you use this  then your controller does not need a HttpServletResponse object  and therefore it is easier to test   Except this  this answer is relative equals to the one of Infeligo   If the return value of your pdf framework is an byte array  read the second part of my answer for other return values      RequestMapping value     files  fileName    method   RequestMethod GET  public HttpEntity lt byte   gt  createPdf                    PathVariable  fileName   String fileName  throws IOException        byte   documentBody   this pdfFramework createPdf filename        HttpHeaders header   new HttpHeaders        header setContentType MediaType APPLICATION PDF       header set HttpHeaders CONTENT DISPOSITION                      attachment  filename     fileName replace                 header setContentLength documentBody length        return new HttpEntity lt byte   gt  documentBody  header         If the return type of your PDF Framework  documentBbody  is not already a byte array  and also no ByteArrayInputStream  then it would been wise NOT to make it a byte array first  Instead it is better to use    InputStreamResource  PathResource  since Spring 4 0  or FileSystemResource     example with FileSystemResource    RequestMapping value     files  fileName    method   RequestMethod GET  public HttpEntity lt byte   gt  createPdf                    PathVariable  fileName   String fileName  throws IOException        File document   this pdfFramework createPdf filename        HttpHeaders header   new HttpHeaders        header setContentType MediaType APPLICATION PDF       header set HttpHeaders CONTENT DISPOSITION                      attachment  filename     fileName replace                 header setContentLength document length          return new HttpEntity lt byte   gt  new FileSystemResource document                                     header

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You should be able to write the file on the response directly  Something like   response setContentType  application pdf          response setHeader  Content-Disposition    attachment  filename   somefile pdf         and then write the file as a binary stream on response getOutputStream    Remember to do response flush   at the end and that should do it

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Below code worked for me to generate and download a text file    RequestMapping value     download   method   RequestMethod GET  public ResponseEntity lt byte   gt  getDownloadData   throws Exception        String regData    Lorem Ipsum is simply dummy text of the printing and typesetting industry  Lorem Ipsum has been the industry s standard dummy text ever since the 1500s  when an unknown printer took a galley of type and scrambled it to make a type specimen book  It has survived not only five centuries  but also the leap into electronic typesetting  remaining essentially unchanged  It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages  and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum        byte   output   regData getBytes         HttpHeaders responseHeaders   new HttpHeaders        responseHeaders set  charset    utf-8        responseHeaders setContentType MediaType valueOf  text html         responseHeaders setContentLength output length       responseHeaders set  Content-disposition    attachment  filename filename txt         return new ResponseEntity lt byte   gt  output  responseHeaders  HttpStatus OK

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This can be a useful answer   Is it ok to export data as pdf format in frontend   Extending to this  adding content-disposition as an attachment default  will download the file  If you want to view it  you need to set it to inline

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something like below   RequestMapping value     download   method   RequestMethod GET  public void getFile HttpServletResponse response        try           DefaultResourceLoader loader   new DefaultResourceLoader            InputStream is   loader getResource  classpath META-INF resources Accepted pdf   getInputStream            IOUtils copy is  response getOutputStream             response setHeader  Content-Disposition    attachment  filename Accepted pdf            response flushBuffer          catch  IOException ex            throw new RuntimeException  IOError writing file to output stream              You can display PDF or download it examples here

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What I can quickly think of is  generate the pdf and store it in webapp downloads  lt  RANDOM-FILENAME  pdf from the code and send a forward to this file using HttpServletRequest  request getRequestDispatcher   downloads  lt RANDOM-FILENAME gt  pdf   forward request  response     or if you can configure your view resolver something like       lt bean id  pdfViewResolver          class  org springframework web servlet view InternalResourceViewResolver  gt       lt property name  viewClass                value  org springframework web servlet view JstlView    gt       lt property name  order  value    2   gt       lt property name  prefix  value   downloads     gt       lt property name  suffix  value   pdf    gt     lt  bean gt    then just return   return  RANDOM-FILENAME

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I was able to stream line this by using the built in support in Spring with it s ResourceHttpMessageConverter   This will set the content-length and content-type if it can determine the mime-type   RequestMapping value     files  file name    method   RequestMethod GET   ResponseBody public FileSystemResource getFile  PathVariable  file name   String fileName        return new FileSystemResource myService getFileFor fileName

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RequestMapping value     files  file name    method   RequestMethod GET  public void getFile       PathVariable  file name   String fileName       HttpServletResponse response        try            get your file as InputStream       InputStream is                 copy it to response s OutputStream       org apache commons io IOUtils copy is  response getOutputStream           response flushBuffer          catch  IOException ex          log info  Error writing file to output stream  Filename was        fileName  ex         throw new RuntimeException  IOError writing file to output stream               Generally speaking  when you have response getOutputStream    you can write anything there  You can pass this output stream as a place to put generated PDF to your generator  Also  if you know what file type you are sending  you can set   response setContentType  application pdf

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This code is working fine to download a file automatically from spring controller on clicking a link on jsp         RequestMapping value   downloadLogFile   public void getLogFile HttpSession session HttpServletResponse response  throws Exception       try           String filePathToBeServed     complete file name with path          File fileToDownload   new File filePathToBeServed           InputStream inputStream   new FileInputStream fileToDownload           response setContentType  application force-download            response setHeader  Content-Disposition    attachment  filename   fileName   txt             IOUtils copy inputStream  response getOutputStream             response flushBuffer            inputStream close          catch  Exception e           LOGGER debug  Request could not be completed at this moment  Please try again             e printStackTrace

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If you   Don t want to load the whole file into a byte   before sending to the response  Want need to send download it via InputStream  Want to have full control of the Mime Type and file name sent  Have other  ControllerAdvice picking up exceptions for you  or not    The code below is what you need   RequestMapping value    quot  stuff  stuffId  quot   method   RequestMethod GET  public ResponseEntity lt FileSystemResource gt  downloadStuff  PathVariable int stuffId                                                                        throws IOException       String fullPath   stuffService figureOutFileNameFor stuffId       File file   new File fullPath       long fileLength   file length       this is ok  but see note below      HttpHeaders respHeaders   new HttpHeaders        respHeaders setContentType  quot application pdf quot        respHeaders setContentLength fileLength       respHeaders setContentDispositionFormData  quot attachment quot    quot fileNameIwant pdf quot         return new ResponseEntity lt FileSystemResource gt           new FileSystemResource file   respHeaders  HttpStatus OK           More on setContentLength    First of all  the content-length header is optional per the HTTP 1 1 RFC  Still  if you can provide a value  it is better  To obtain such value  know that File length   should be good enough in the general case  so it is a safe default choice  In very specific scenarios  though  it can be slow  in which case you should have it stored previously  e g  in the DB   not calculated on the fly  Slow scenarios include  if the file is very large  specially if it is on a remote system or something more elaborated like that - a database  maybe    InputStreamResource If your resource is not a file  e g  you pick the data up from the DB  you should use InputStreamResource  Example      InputStreamResource isr   new InputStreamResource new FileInputStream file        return new ResponseEntity lt InputStreamResource gt  isr  respHeaders  HttpStatus OK

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Return ResponseEntity lt Resource gt  from a handler method Specify Content-Type explicitly Set Content-Disposition if necessary   filename type  inline to force preview in a browser attachment to force a download       Controller public class DownloadController        GetMapping  quot  downloadPdf pdf quot          1      public ResponseEntity lt Resource gt  downloadPdf             FileSystemResource resource   new FileSystemResource  quot  home caco3 Downloads JMC Tutorial pdf quot               2          MediaType mediaType   MediaTypeFactory                  getMediaType resource                   orElse MediaType APPLICATION OCTET STREAM           HttpHeaders headers   new HttpHeaders            headers setContentType mediaType              3         ContentDisposition disposition   ContentDisposition                    3 2                  inline      or  attachment                      3 1                  filename resource getFilename                     build            headers setContentDisposition disposition           return new ResponseEntity lt  gt  resource  headers  HttpStatus OK            Explanation Return ResponseEntity lt Resource gt  When you return a ResponseEntity lt Resource gt   the ResourceHttpMessageConverter kicks in and writes an appropriate response  The resource could be   ByteArrayResource FileSystemResource UrlResource or even GridFsResource  Be aware of possibly wrong Content-Type header set  see FileSystemResource is returned with content type json   That s why this answer suggests setting the Content-Type explicitly  Specify Content-Type explicitly  Some options are   hardcode the header use the MediaTypeFactory from Spring  or rely on third party library like Apache Tika  The MediaTypeFactory allows to discover the MediaType appropriate for the Resource  see also  org springframework http mime types file  Set Content-Disposition if necessary  Sometimes it is necessary to force a download in a browser or to make the browser open a file as a preview  You can use the Content-Disposition header to satisfy this requirement   The first parameter in the HTTP context is either inline  default value  indicating it can be displayed inside the Web page  or as the Web page  or attachment  indicating it should be downloaded  most browsers presenting a  Save as  dialog  prefilled with the value of the filename parameters if present    In the Spring Framework a ContentDisposition can be used  To preview a file in a browser  ContentDisposition disposition   ContentDisposition          builder  quot inline quot      Or  inline   if you re on Spring MVC 5 3           filename resource getFilename             build     To force a download  ContentDisposition disposition   ContentDisposition          builder  quot attachment quot      Or  attachment   if you re on Spring MVC 5 3           filename resource getFilename             build     Use InputStreamResource carefully  Since an InputStream can be read only once  Spring won t write Content-Length header if you return an InputStreamResource  here is a snippet of code from ResourceHttpMessageConverter    Override protected Long getContentLength Resource resource   Nullable MediaType contentType  throws IOException          Don t try to determine contentLength on InputStreamResource - cannot be read afterwards           Note  custom InputStreamResource subclasses could provide a pre-calculated content length      if  InputStreamResource class    resource getClass              return null            long contentLength   resource contentLength        return  contentLength  lt  0   null   contentLength      In other cases it works fine      curl -I localhost 8080 downloadPdf pdf    grep  quot Content-Length quot  Content-Length  7554270

User · Answer

If it helps anyone  You can do what the accepted answer by Infeligo has suggested but just put this extra bit in the code for a forced download   response setContentType  application force-download

User · Answer

The following solution work for me       RequestMapping value   download       public void getLogFile HttpSession session HttpServletResponse response  throws Exception           try                String fileName  archivo demo pdf               String filePathToBeServed    C   software  Tomcat 7 0  tmpFiles                 File fileToDownload   new File filePathToBeServed fileName                InputStream inputStream   new FileInputStream fileToDownload               response setContentType  application force-download                response setHeader  Content-Disposition    attachment  filename   fileName                IOUtils copy inputStream  response getOutputStream                 response flushBuffer                inputStream close              catch  Exception exception               System out println exception getMessage

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