Send a file from server to client in GWT

Question

I am using GWT.

I have to download a file file from server to client.

Document is in the external repository.

Client sends the id of the document through a Servlet.

On server side: Using this ID document is retrieved:

Document document = (Document)session.getObject(docId);
ContentStream contentStream = document.getContentStream();

ByteArrayInputStream inputStream = (ByteArrayInputStream) contentStream.getStream();

int c;
while ((c = inputStream.read()) != -1) {
    System.out.print((char) c); 
}
String mime = contentStream.getMimeType();
String name = contentStream.getFileName();
InputStream strm = contentStream.getStream();

Here I can read the document.

I want to send this to the client. How do I make this a file and send it back to the client?

Hardik Mishra · Accepted Answer · 2012-08-24T15:46:11.223

3

In Your Servlet:

Document document =(Document)session.getObject(docId);
ContentStream contentStream = document.getContentStream();
String name = contentStream.getFileName();
response.setHeader("Content-Type", "application/octet-stream;");
response.setHeader("Content-Disposition", "attachment;filename=\"" + name + "\"");
OutputStream os = response.getOutputStream();
InputStream is = 
  (ByteArrayInputStream) contentStream.getStream();
BufferedInputStream buf = new BufferedInputStream(is);
int readBytes=0;
while((readBytes=buf.read())!=-1) {
      os.write(readBytes);
}   
os.flush();
os.close();// *important*
return;

edited Aug 24 '12 at 15:46

answered Aug 24 '12 at 14:18

Hardik Mishra

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: All the files which are dowloded from server to client is empty but the files are not Empty. – GameBuilder Aug 24 '12 at 15:18
I have edited answer. Try now and Check you re getting data in `contentStream.getStream()` which is your code. – Hardik Mishra Aug 24 '12 at 15:31
:What is input. `new BufferedInputStream(input);` – GameBuilder Aug 24 '12 at 15:37
Oh Sorry Typo: It should be "is" – Hardik Mishra Aug 24 '12 at 15:40
:`byte[] buf = new BufferedInputStream(inputStream);` this line is giving me error Type mismatch: cannot convert from BufferedInputStream to byte[] Change type to buf BufferInputStream – GameBuilder Aug 24 '12 at 15:43
Ok. Actually I have not tried running the code. It should work now. – Hardik Mishra Aug 24 '12 at 15:45
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/15767/discussion-between-hardik-mishra-and-gamebuilder) – Hardik Mishra Aug 24 '12 at 15:48
I have `FormhandlerEvent onSubmitComplete event `i tried to print something. But it doesnt. I tried to debug it. but the debugger never enters the `onSubmitComple Event`. – GameBuilder Aug 24 '12 at 16:38

kapandron · Answer 2 · 2012-08-24T15:11:12.230

You can create a standard servlet (which extends HttpServlet and not RemoteServiceServlet) on server side and opportunity to submit the id as servlet parameter on client side.

Now you need after getting request create the excel file and send it to the client. Browser shows automatically popup with download dialog box. But you should make sure that you set the right content-type response headers. This header will instruct the browser which type of file is it.

protected void doGet(HttpServletRequest request, HttpServletResponse response) 
                                              throws ServletException, IOException { 

String fileId = reguest.getParameter("fileId"); // value of file id from request
File file = CreatorExel.getFile(fileId); // your method to create file from helper class

// setting response headers
response.setHeader("Content-Type", getServletContext().getMimeType(file.getName())); 
response.setHeader("Content-Length", file.length()); 
response.setHeader("Content-Disposition", "inline; filename=\"" + file.getName() + "\""); 

BufferedInputStream input = null; 
BufferedOutputStream output = null; 

try { 
    InputStream inputStream = new FileInputStream(file);
    ServletOutputStream outputStream = response.getOutputStream();

    input = new BufferedInputStream(fileInput); 
    output = new BufferedOutputStream(outputStream); 

    int count;
    byte[] buffer = new byte[8192]; //  buffer size is 512*16
    while ((count = input.read(buffer)) > 0) {
         output.write(buffer, 0, count);
    }

} finally { 
    if (output != null) {
       try { 
          output.close(); 
       } catch (IOException ex) {
       } 
    }
    if (input != null) {
       try { 
          input.close(); 
       } catch (IOException ex) {
       } 
    } 
}

Send a file from server to client in GWT

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