I know this is a little broad, but here's the situation:
I am using JSP and Java. I have a file located on my server. I would like to add a link to the screen that, when clicked, would open the file for the user to view. The file can either appear in a window in the web browser, or pop up the program needed to open the file (similar to when you are outputting with iText to the screen, where Adobe opens to display the file). I know my output stream already, but how can I write the file to the output stream? Most of what I have read has only dealt with text files, but I might be dealing with image files, etc., as well.
Any help is appreciated!
Thanks!
You need to add certain fields to the response. For a text/csv, you'd do:
response.setContentType("text/csv"); // set MIME type
response.setHeader("Content-Disposition", "attachment; filename=\"" strExportFileName "\"");
Here's a forum on sun about it.
Here's a simple implementation on how to achieve it:
protected void doPost(final HttpServletRequest request,
final HttpServletResponse response) throws ServletException,
IOException {
// extract filename from request
// TODO use a whitelist to avoid [path-traversing][1]
File file = new File(getFileName(request));
InputStream input = new FileInputStream(file);
response.setContentLength((int) file.length());
// TODO map your file to the appropriate MIME
response.setContentType(getMimeType(file));
OutputStream output = response.getOutputStream();
byte[] bytes = new byte[BUFFER_LENGTH];
int read = 0;
while (read != -1) {
read = input.read(bytes, 0, BUFFER_LENGTH);
if (read != -1) {
output.write(bytes, 0, read);
output.flush();
}
}
input.close();
output.close();
}
You need to create a 'download' servlet which writes the file to the response output stream with correct mime types. You can not reliably do this from within a .jsp file.
We usually do it with a 'download servlet' which we set the servletmapping to /downloads, then append path info to identify the asset to serve. The servlet verifies the request is valid, sets the mime header then delivers the file to the output stream. It's straightforward, but keep the J2EE javadocs handy while doing it.
Related
How to download all files in the file directory when clicking the export or download at the same time？
At present, all the files in the file directory have been obtained, then all the files are placed in the list, and then the stream is written after traversing all the files. However, when importing the second file, it will report cannot reset buffer after response has been committed
The source of the problem is in this code： // response.reset();
Code：
String filePath = "/code/data/";
// Get all file addresses of the directory
List<String> filePathList = getFilePath(filePath);
//Create thread pool
for (String str : filePathList){
download(request, response, str);
}
private void download(HttpServletRequest request,
HttpServletResponse response,String filePath) {
File file = new File(filePath);
//Gets the file name.
String fileName = file.getName();
InputStream fis = null;
try {
fis = new FileInputStream(file);
request.setCharacterEncoding("UTF-8");
String agent = request.getHeader("User-Agent").toUpperCase();
if ((agent.indexOf("MSIE") > 0) || ((agent.indexOf("RV") != - 1) &&
(agent.indexOf("FIREFOX") == -1))) {
fileName = URLEncoder.encode(fileName, "UTF-8");
} else {
fileName = new String(fileName.getBytes("UTF-8"), "ISO8859-1");
}
// response.reset();
response.setCharacterEncoding("UTF-8");
response.setContentType("application/force-download");
// Set forced download not to open
response.addHeader("Content-Disposition",
"attachment; filename=" + fileName);
response.setHeader("Content-Length", String.valueOf(file.length()));
byte[] b = new byte[1024];
int len;
while ((len = fis.read(b)) != - 1) {
response.getOutputStream().write(b, 0, len);
}
response.flushBuffer();
fis.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
What are the good solutions Thanks
I have not read your code in detail because the bad formatting makes my head hurt.
However, from a superficial reading, it looks like this server-side code is trying to deliver multiple files in response to a single HTTP request.
AFAIK, that is not possible. The HTTP request / response model does not support this. It certainly does not allow a servlet to:
change response headers after the response output stream has been opened
do anything after the response output stream has been closed.
(Your code appears to be trying to do both of those things!)
So, you have to do it differently. Here are some possibilities:
On the server side, assemble all of the files to be downloaded into (say) a temporary ZIP file and then send that. Leave it to the user to unpack the ZIP file ... or not ... as they want.
This is often the best approach. Imagine how annoyed you would be if a few thousand separate files unexpectedly landed in your web browser's Downloads folder.
As 1. and also do something on the client side to transparently unpack the files from the ZIP and put them in the right place in the client's file system.
The "something" could be custom javascript embedded in the web page, or a custom client implemented in Java ... or any other language. (But in the former case, there may be a security issue in allowing sandboxed javascript to write files in arbitrary places without the user confirming each file ... tedious.)
You might be able to send a "multipart" document as the response. However from what I have read, most browsers don't support multipart for downloads; e.g. some browsers will discard all but the last part. (Note: multipart is not designed for this purpose ...)
Change things so that an HTTP request only downloads one file at a time from the directory, and add some client-side stuff to 1) fetch a list of files from the server and iterate the list, fetching each file.
See also: Download multiple files with a single action
I have a database where the user doesn't has access to.
Still I can go to the database and "read" the documents with for example
var db:NotesDatabase = sessionAsSigner.getDatabase("","somedir/some.nsf");
In this database there's a pdf file I would like to open or download. I have the filename and the unid . If the user had acces to the database I could do it with
http(s)://[yourserver]/[application.nsf] /xsp/.ibmmodres/domino/OpenAttachment/ [application.nsf]/[UNID|/$File/[AttachmentName]?Open
How can I do it with sessionAsSigner without putting a $PublicAccess=1 field on the form ?
edit:
the pdf file is stored as attachment in a richtextfield
second edit
I'm trying to use the XSnippet from Naveen and made some changes
The error message I get is : 'OutStream' not found
The code I tried is :
response.reset();
response.setContentType("application/pdf");
response.setHeader("Content-Disposition", "inline; filename=" + zipFileName);
var embeddedObj:NotesEmbeddedObject = null;
var bufferInStream:java.io.BufferedInputStream = null;
var outStream:java.io.OutputStream = response.getOutputStream();
embeddedObj = downloadDocument.getAttachment(fileName);
if (embeddedObj != null) {
bufferInStream = new java.io.BufferedInputStream(embeddedObj.getInputStream());
var bufferLength = bufferInStream.available();
var data = new byte[bufferLength];
bufferInStream.read(data, 0, bufferLength); // Read the attachment data
ON THE NEXT LINE IS THE PROBLEM
OutStream.write(data); // Write attachment into pdf
bufferInStream.close();
embeddedObj.recycle();
}
downloadDocument.recycle();
outStream.flush();
outStream.close();
facesContext.responseComplete();
Create an XAgent (= XPage without rendering) which takes datebase + documentid + filename as URL parameters and delivers the file as response OutputStream.
The URL would be
http(s)://[yourserver]/download.nsf/download.xsp?db=[application.nsf]&unid=[UNID]&attname=[AttachmentName]
for an XAgent download.xsp in a database download.nsf.
The code behind the XAgent runs as sessionAsSigner and is able to read the file even the user itself has no right to access file's database.
Use Eric's blog (+ Java code) as a starting point. Replace "application/json" with "application/pdf" and stream pdf file instead of json data.
As an alternative you can adapt this XSnippet code from Thomas Adrian. Use download() together with grabFile() to write your pdf-File to OutputStream.
Instead of extracting attachment file to path and reading it from there you can stream the attachment right from document to response's OutputStream. Here is an XSnippet from Naveen Maurya as a good example.
If you can get the PDF file as a stream, you should be able to use the OutputStream of the external context's response.
Stephan Wissel has a blog posting about writing out an ODF file so you should be able to cut that up as a starting point.
http://www.wissel.net/blog/d6plinks/SHWL-8248MT
You already have the db so, you will just need to know the UNID of the document.
var doc = db.getDocumentByUNID(unid) 'unid is a supplied param
var itm:RichTextItem = doc.getFirstItem("Body") 'assuming file is in body field
Once you have the itm, you can loop round all of the embeddedObjects and get the pdf file. At this point, I don't know if you can stream it directly or if you have to detach it, but assuming you detach it, you will then use something like this.
File file = new File("path to file");
FileInputStream fileIn = new FileInputStream(file);
Don't forget to clean up the temporarily detached file
We have the below requirement.
We will have to create an excel/pdf report and then download it on click of a button in a java web application. The pdf/excel file is dynamically created using application data.
We should not create any physical file on the server.
How do we go about this? Are there any streams through which I can read and write in the same go without having to close in between.
You could use memory-based streams (such as ByteArrayInputStream and ByteArrayOutputStream) and use the same underlying byte buffer to address the read/write in the same go part of the question.
As others have pointed out, you can just write directly to the output stream of the response.
Look at ServletResponse.getOutputStream().
You need to write to this stream from the one created by your report API. Don't forget to set the proper content-type using setContentType() method of the same class.
Here you can find how you can do it with jxl API and it may help you also.
How do I output an Excel file from a Servlet?
Whatever PDF or Excel API you are using to generate the files, you should lookup the constructor or method which takes an OutputStream to write the generated PDF/Excel content to. You should just feed it with response.getOutputStream() instead of FileOutputStream.
For example, iText for PDFs:
response.setContentType("application/pdf");
response.setHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");
PdfWriter pdfWriter = PdfWriter.getInstance(document, response.getOutputStream());
// ...
And Apache POI for Excel:
response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");
WritableWorkbook workBook = Workbook.createWorkbook(response.getOutputStream());
// ...
Have a Servlet serve the pdf/excel file as a byte array.
#Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
byte[] bytes = null; // get this from somewhere in your app
String fileName = "filename.pdf"; // whatever you wish to name the file
ServletOutputStream out = response.getOutputStream();
response.setHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
response.setContentType("application/pdf");
response.setContentLength(bytes.length);
out.write(bytes);
out.flush();
}
MIME type for MS Excel files would be application/vnd.ms-excel.
When I want to write the full contents of a file into an OutputStream, I usually allocate a buffer as a byte[], then make a for loop to read data from the file's InputStream into the buffer and write the buffer contents into the OutputStream, until the InputStream has no more bytes available.
This seems rather clumsy to me. Is there a better way to do this?
Also, I am always unsure about the buffer size. Usually, I am allocating 1024 bytes, because it just feels good. Is there a better way to determine a reasonable buffer size?
In my current case, I want to copy the full contents of a file into the output stream that writes the contents of an HTTP response. So, this is not a question about how to copy files on the file system.
For Java 1.7+ you can use the Files.copy(Path, OutputStream), e.g.
HttpServletResponse response = // ...
File toBeCopied = // ...
try (OutputStream out = response.getOutputStream()) {
Path path = toBeCopied.toPath();
Files.copy(path, out);
out.flush();
} catch (IOException e) {
// handle exception
}
Note, since you are dealing with HttpServletResponse is is also a good idea to set correct response headers. Add the following lines before you copy the actual file data to the response:
String mimeType = URLConnection.guessContentTypeFromName(toBeCopied.getName());
String contentDisposition = String.format("attachment; filename=%s", toBeCopied.getName());
int fileSize = Long.valueOf(toBeCopied.length()).intValue();
response.setContentType(mimeType);
response.setHeader("Content-Disposition", contentDisposition);
response.setContentLength(fileSize);
Note, the encoding of the file name passed to the content disposition is important, see this question.
Apache Commons-IO:
IOUtils.copy(fileInputStream,outputStream);
JDK NIO
new FileInputStream(file).getChannel().transferTo(otherChannel);
With commons-io you have a one-line solution:
IOUtils.copy(yourFileInputStream, outputStream);
Note that you'd have to close your streams manually (or by IOUtils.closeQuitely(..))
I have implemented RPCService, RPCServiceAsync & RPCServieImpl. On clicking a button a service in server side will be called and it will fetch data from DB and file is created. Once the file is created, then i need to open that file in client side and need to prompt a dialog box with open/save options.
how can i implement this opening a file part. pls suggest a way to implement t.. Reply pls.. thanks in advance....
#Hambend : I still have one more clarification !.. how to call this doGet method in another servlet i.e. in my onmodule load class i am having lot of widgets in seperate layout and one such a widget is BUTTON ? onclicking this button service RPCServiceImpl is called and all manipulations are done and file is created in a serperate function (public int GenerateFile(String name)() ) . how to make that function to call doGet method ? since doGet needs request,response parameters to be passed along with it?? pls suggest me a method to call that method. thanks in advance
GWT's RPC services are only able to send java objects back to the client. To send a file back to the user you'll need to use a non-GWT java servlet. Here's some code I've used before for serving up jpeg images from a repository.
public class ImageServlet extends HttpServlet {
private final String repository = "/var/images/";
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String filename = request.getParameter("file");
// Security: '..' in the filename will let sneaky users access files
// not in your repository.
filename = filename.replace("..", "");
File file = new File(repository + filename);
if (!file.exists())
throw new FileNotFoundException(file.getAbsolutePath());
response.setHeader("Content-Type", "image/jpeg");
response.setHeader("Content-Length", String.valueOf(file.length()));
response.setHeader("Content-disposition", "attachment;filename=\"" + filename + "\"");
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));
BufferedOutputStream bos = new BufferedOutputStream(response.getOutputStream());
byte[] buf = new byte[1024];
while (true) {
int length = bis.read(buf);
if (length == -1)
break;
bos.write(buf, 0, length);
}
bos.flush();
bos.close();
bis.close();
}
}
"Content-disposition: attachment" should cause most browsers to download the file instead of displaying it, with the filename defaulting to whatever you provide. The way you would use this servlet is to have the user call the RPCService that you already have, which saves the file to the repository folder. Then, you link or redirect them to this servlet with a url such as http://your.domain.com/fileServlet?file=myFile.jpg. Obviously with this setup you have a security risk where users can download other people's files if they can guess the filenames.
What you might like to do is merge the database code from your RPC service into this servlet. There's no need to save the file anywhere on the server, you can take your database results and write them into response.getOutputStream() or response.getWriter() in exactly the same way you would write them to file, except that the result goes straight to the user. As long as you set your content headers correctly the user won't notice the difference.
You can't call this method from another servlet, the only way to make a browser to download it as a file is to access it through a normal HTTP request. First you declare the servlet in your web.xml file like you would a GWT RPC service:
<servlet>
<servlet-name>ImageServlet</servlet-name>
<servlet-class>
com.package.ImageServlet
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ImageServlet</servlet-name>
<url-pattern>/imageServlet</url-pattern>
</servlet-mapping>
Now any HTTP GET requests going to http://your.tomcat.server/webapp/imageServlet will get picked up by ImageServlet.doGet(). Then on the client side you can either make a normal html link to the file:
new HTML("<a href='" + GWT.getHostPageBaseURL() + "imageServlet?file=" + filename + "'>download</a>");
...or, you should be able to put this in a ClickHandler (I haven't tested it):
Window.Location.assign(GWT.getHostPageBaseURL() + "imageServlet?file=" + filename);
If the file is text, then you always back back an Object with an array of Strings.
If binary then simply a byte[] in the class would do.