By zmeda


2012-02-22 09:07:11 8 Comments

Is there any way of providing a file download from a JSF backing bean action method? I have tried a lot of things. Main problem is that I cannot figure how to get the OutputStream of the response in order to write the file content to. I know how to do it with a Servlet, but this cannot be invoked from a JSF form and requires a new request.

How can I get the OutputStream of the response from the current FacesContext?

4 comments

@BalusC 2012-02-22 11:52:31

Introduction

You can get everything through ExternalContext. In JSF 1.x, you can get the raw HttpServletResponse object by ExternalContext#getResponse(). In JSF 2.x, you can use the bunch of new delegate methods like ExternalContext#getResponseOutputStream() without the need to grab the HttpServletResponse from under the JSF hoods.

On the response, you should set the Content-Type header so that the client knows which application to associate with the provided file. And, you should set the Content-Length header so that the client can calculate the download progress, otherwise it will be unknown. And, you should set the Content-Disposition header to attachment if you want a Save As dialog, otherwise the client will attempt to display it inline. Finally just write the file content to the response output stream.

Most important part is to call FacesContext#responseComplete() to inform JSF that it should not perform navigation and rendering after you've written the file to the response, otherwise the end of the response will be polluted with the HTML content of the page, or in older JSF versions, you will get an IllegalStateException with a message like getoutputstream() has already been called for this response when the JSF implementation calls getWriter() to render HTML.

Turn off ajax / don't use remote command!

You only need to make sure that the action method is not called by an ajax request, but that it is called by a normal request as you fire with <h:commandLink> and <h:commandButton>. Ajax requests and remote commands are handled by JavaScript which in turn has, due to security reasons, no facilities to force a Save As dialogue with the content of the ajax response.

In case you're using e.g. PrimeFaces <p:commandXxx>, then you need to make sure that you explicitly turn off ajax via ajax="false" attribute. In case you're using ICEfaces, then you need to nest a <f:ajax disabled="true" /> in the command component.

Generic JSF 2.x example

public void download() throws IOException {
    FacesContext fc = FacesContext.getCurrentInstance();
    ExternalContext ec = fc.getExternalContext();

    ec.responseReset(); // Some JSF component library or some Filter might have set some headers in the buffer beforehand. We want to get rid of them, else it may collide.
    ec.setResponseContentType(contentType); // Check http://www.iana.org/assignments/media-types for all types. Use if necessary ExternalContext#getMimeType() for auto-detection based on filename.
    ec.setResponseContentLength(contentLength); // Set it with the file size. This header is optional. It will work if it's omitted, but the download progress will be unknown.
    ec.setResponseHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\""); // The Save As popup magic is done here. You can give it any file name you want, this only won't work in MSIE, it will use current request URL as file name instead.

    OutputStream output = ec.getResponseOutputStream();
    // Now you can write the InputStream of the file to the above OutputStream the usual way.
    // ...

    fc.responseComplete(); // Important! Otherwise JSF will attempt to render the response which obviously will fail since it's already written with a file and closed.
}

Generic JSF 1.x example

public void download() throws IOException {
    FacesContext fc = FacesContext.getCurrentInstance();
    HttpServletResponse response = (HttpServletResponse) fc.getExternalContext().getResponse();

    response.reset(); // Some JSF component library or some Filter might have set some headers in the buffer beforehand. We want to get rid of them, else it may collide.
    response.setContentType(contentType); // Check http://www.iana.org/assignments/media-types for all types. Use if necessary ServletContext#getMimeType() for auto-detection based on filename.
    response.setContentLength(contentLength); // Set it with the file size. This header is optional. It will work if it's omitted, but the download progress will be unknown.
    response.setHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\""); // The Save As popup magic is done here. You can give it any file name you want, this only won't work in MSIE, it will use current request URL as file name instead.

    OutputStream output = response.getOutputStream();
    // Now you can write the InputStream of the file to the above OutputStream the usual way.
    // ...

    fc.responseComplete(); // Important! Otherwise JSF will attempt to render the response which obviously will fail since it's already written with a file and closed.
}

Common static file example

In case you need to stream a static file from the local disk file system, substitute the code as below:

File file = new File("/path/to/file.ext");
String fileName = file.getName();
String contentType = ec.getMimeType(fileName); // JSF 1.x: ((ServletContext) ec.getContext()).getMimeType(fileName);
int contentLength = (int) file.length();

// ...

Files.copy(file.toPath(), output);

Common dynamic file example

In case you need to stream a dynamically generated file, such as PDF or XLS, then simply provide output there where the API being used expects an OutputStream.

E.g. iText PDF:

String fileName = "dynamic.pdf";
String contentType = "application/pdf";

// ...

Document document = new Document();
PdfWriter writer = PdfWriter.getInstance(document, output);
document.open();
// Build PDF content here.
document.close();

E.g. Apache POI HSSF:

String fileName = "dynamic.xls";
String contentType = "application/vnd.ms-excel";

// ...

HSSFWorkbook workbook = new HSSFWorkbook();
// Build XLS content here.
workbook.write(output);
workbook.close();

Note that you cannot set the content length here. So you need to remove the line to set response content length. This is technically no problem, the only disadvantage is that the enduser will be presented an unknown download progress. In case this is important, then you really need to write to a local (temporary) file first and then provide it as shown in previous chapter.

Utility method

If you're using JSF utility library OmniFaces, then you can use one of the three convenient Faces#sendFile() methods taking either a File, or an InputStream, or a byte[], and specifying whether the file should be downloaded as an attachment (true) or inline (false).

public void download() throws IOException {
    Faces.sendFile(file, true);
}

Yes, this code is complete as-is. You don't need to invoke responseComplete() and so on yourself. This method also properly deals with IE-specific headers and UTF-8 filenames. You can find source code here.

@Lyubomyr Shaydariv 2012-11-13 18:45:58

So easy! I've been wondering how to make the download available for PrimeFaces according to their showcase, because it requires InputStream infrastructure for p:fileDownload, and I haven't managed how to convert OutputStream to InputStream. Now it's clear that even an action listener can change the response content type and then the response will be respected as a file download at the user-agent side anyway. Thank you!

@Alfredo Osorio 2013-02-13 18:54:24

Is there a way to do this using a HTTP GET instead of HTTP POST (h:commandButton and h:commandLink)?

@BalusC 2013-02-13 18:55:54

@Alfredo: yes, using preRenderView listener in a markupless view. Similar question for downloading (well, serving) JSON is answered here: stackoverflow.com/questions/8358006/…

@Zakhar 2013-04-28 12:59:42

w3schools.com/media/media_mimeref.asp link is broken. Maybe this one is suitable: iana.org/assignments/media-types

@StudioWorks 2015-03-11 12:58:39

@BalusC How do I stream multiple files? I've put this inside a for, but the first file keeps "downloading" until the entire for is complete and then only the contents of the first file are streamed to download.

@BalusC 2015-03-11 13:48:04

@StudioWorks: You can return only 1 response per request. Zip it.

@DannyThunder 2016-04-07 14:10:43

How to do this with PDF? "java.lang.IllegalArgumentException: application/pdf is an unsupported content type"

@BalusC 2016-04-07 14:14:08

Hard to tell without stack trace. This exception is at least not recognizable as part of standard JSF. In standard JSF on a normal servlet environment it should just work right away.

@DannyThunder 2016-04-07 14:19:15

@BalusC Aaa! My bad! It seem to be a Liferay mime type issue!

@Buttinger Xaver 2017-09-12 14:35:25

@BalusC you cover every jsf topic - thank you for making my life easier sir!

@erickdeoliveiraleal 2018-07-09 19:20:13

@BalusC When using Generic JSF 2.x example using Content-Disposition: inline I can save it on Chrome, But using OmniFaces sendFile I can't download after view it.it says: network error. looks like it is related to cache control

@azro 2018-07-23 08:52:29

I want to download 2 files but not zip, I tried to call twice the download method, one after another, but I got exception on the second, IllegalStateException, how do deal with this ?

@BalusC 2018-07-23 16:00:07

@azro: Don't call download method twice on same request. This makes no sense. The file contents will come after each other in the same response and basically return a (corrupted) single file. Just let client fire two requests.

@Koray Tugay 2017-04-28 09:06:43

This is what worked for me:

public void downloadFile(String filename) throws IOException {
    final FacesContext fc = FacesContext.getCurrentInstance();
    final ExternalContext externalContext = fc.getExternalContext();

    final File file = new File(filename);

    externalContext.responseReset();
    externalContext.setResponseContentType(ContentType.APPLICATION_OCTET_STREAM.getMimeType());
    externalContext.setResponseContentLength(Long.valueOf(file.lastModified()).intValue());
    externalContext.setResponseHeader("Content-Disposition", "attachment;filename=" + file.getName());

    final HttpServletResponse response = (HttpServletResponse) externalContext.getResponse();

    FileInputStream input = new FileInputStream(file);
    byte[] buffer = new byte[1024];
    final ServletOutputStream out = response.getOutputStream();

    while ((input.read(buffer)) != -1) {
        out.write(buffer);
    }

    out.flush();
    fc.responseComplete();
}

@ÖMER TAŞCI 2018-08-13 08:47:59

After 2 work days, this solved my problem with a little changes:) thank you very much.

@Kukeltje 2019-01-28 12:16:05

@ÖMERTAŞCI: What changes,

@John Mendes 2016-10-03 10:01:56

public void download() throws IOException
{

    File file = new File("file.txt");

    FacesContext facesContext = FacesContext.getCurrentInstance();

    HttpServletResponse response = 
            (HttpServletResponse) facesContext.getExternalContext().getResponse();

    response.reset();
    response.setHeader("Content-Type", "application/octet-stream");
    response.setHeader("Content-Disposition", "attachment;filename=file.txt");

    OutputStream responseOutputStream = response.getOutputStream();

    InputStream fileInputStream = new FileInputStream(file);

    byte[] bytesBuffer = new byte[2048];
    int bytesRead;
    while ((bytesRead = fileInputStream.read(bytesBuffer)) > 0) 
    {
        responseOutputStream.write(bytesBuffer, 0, bytesRead);
    }

    responseOutputStream.flush();

    fileInputStream.close();
    responseOutputStream.close();

    facesContext.responseComplete();

}

@Bharat Sharma 2013-02-05 10:57:14

here is the complete code snippet http://bharatonjava.wordpress.com/2013/02/01/downloading-file-in-jsf-2/

 @ManagedBean(name = "formBean")
 @SessionScoped
 public class FormBean implements Serializable
 {
   private static final long serialVersionUID = 1L;

   /**
    * Download file.
    */
   public void downloadFile() throws IOException
   {
      File file = new File("C:\\docs\\instructions.txt");
      InputStream fis = new FileInputStream(file);
      byte[] buf = new byte[1024];
      int offset = 0;
      int numRead = 0;
      while ((offset < buf.length) && ((numRead = fis.read(buf, offset, buf.length -offset)) >= 0)) 
      {
        offset += numRead;
      }
      fis.close();
      HttpServletResponse response =
         (HttpServletResponse) FacesContext.getCurrentInstance()
        .getExternalContext().getResponse();

     response.setContentType("application/octet-stream");
     response.setHeader("Content-Disposition", "attachment;filename=instructions.txt");
     response.getOutputStream().write(buf);
     response.getOutputStream().flush();
     response.getOutputStream().close();
     FacesContext.getCurrentInstance().responseComplete();
   }
 }

You may change the file reading logic in case you want file to get generated at runtime.

@hinneLinks 2015-11-04 08:37:26

This will only get you part of the input file, if its larger that 1024 bytes!

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