Request a file with a custom header

Request a file with a custom header - javascript

I have an unusual requirement. Essentially I need a way so that, when the user clicks on a link or button, they will receive a PDF. The tricky part here is that the server won't process the request at all unless a custom header is sent with it (otherwise it deems the person logged out and sends them to the login screen).
At the moment the way the header works cannot be changed so please don't dwell on it; it will get changed in the future and is an internal application that I have no control over.
The options I have explored:
Using an iframe or simply opening a new window with some sort of path that will return the PDF. This can't work because I cannot specify the required header for the PDF and would be redirected before reaching the PDF itself.
Using a form and submitting the request can't work because I can't
add any custom headers to forms (only XHR and plugins can, AFAIK).
Using XHR can't work because, while it can add the header and
retrieve the file, there is no way to save it on the client side.
It would appear my only options at this point are essentially:
Use some sort of plugin such as Flash or Silverlight to request the file.
Force the change of the requirement much earlier than expected so that a header is no longer required.
Is there anything I am missing here? I'm hoping someone can either verify my findings or point me to something I missed because, as far as I can tell, there isn't really anything I can do here.
EDIT: This seems apt and confirms what I was thinking: XMLHttpRequest to open PDF in browser

Tested to work in chrome:
function toBinaryString(data) {
var ret = [];
var len = data.length;
var byte;
for (var i = 0; i < len; i++) {
byte=( data.charCodeAt(i) & 0xFF )>>> 0;
ret.push( String.fromCharCode(byte) );
}
return ret.join('');
}
var xhr = new XMLHttpRequest;
xhr.open( "GET", "/test.pdf" ); //I had test.pdf this on my local server
xhr.addEventListener( "load", function(){
var data = toBinaryString(this.responseText);
data = "data:application/pdf;base64,"+btoa(data);
document.location = data;
}, false);
xhr.setRequestHeader("magic", "header" );
xhr.overrideMimeType( "application/octet-stream; charset=x-user-defined;" );
xhr.send(null);
You can change application/pdf to application/octet-stream to have download prompt. But it's pretty easy to download from the chrome's reader as well.
In firefox nothing happens I guess it's because I don't have a plugin to deal with application/pdf installed. Changing to application/octet-stream will prompt a dl.
With IE I suppose you need some kind of VBScript/ActiveX hackery
If the file is huge, using data uri might crash the browser, in that case you can use BlobBuilder and Object URLs.

Instead of linking to the .PDF file, instead do something like
Download my eBook
which outputs a custom header, opens the PDF (binary safe) and prints the data to the user's browser, then they can choose to save the PDF despite their browser settings. The pdf_server.php should look like this:
header("Content-Type: application/octet-stream");
$file = $_GET["file"] .".pdf";
header("Content-Disposition: attachment; filename=" . urlencode($file));
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");
header("Content-Description: File Transfer");
header("Content-Length: " . filesize($file));
flush(); // this doesn't really matter.
$fp = fopen($file, "r");
while (!feof($fp))
{
echo fread($fp, 65536);
flush(); // this is essential for large downloads
}
fclose($fp);
EDIT: The only way to add headers to a request from inside a browser (client-side) is use the XmlHttpRequest setRequestHeader method.
xhr.setRequestHeader('custom-header', 'value');

Related

Browser XML force download JavaScript [duplicate]

I have some big size PDF catalogs at my website, and I need to link these as download. When I googled, I found such a thing noted below. It should open the "Save As..." popup at link click...
<head>
<meta name="content-disposition" content="inline; filename=filename.pdf">
...
But it doesn't work :/ When I link to a file as below, it just links to file and is trying to open the file.
File name
UPDATE (according to answers below):
As I see there is no 100% reliable cross-browser solution for this. Probably the best way is using one of the web services listed below, and giving a download link...
http://box.net/
http://droplr.com/
http://getcloudapp.com/

From an answer to Force a browser to save file as after clicking link:
<a href="path/to/file" download>Click here to download</a>

Use the download attribute, but take into account that it only works for files hosted in the same origin that your code. It means that users can only download files that are from the origin site, same host.
Download with original filename:
Click here to download
Download with 'some_name' as filename:
Click here to download
Adding target="_blank" we will use a new Tab instead of the actual one, and also it will contribute to the proper behavior of the download attribute in some scenarios.
It follows the same rules as same-origin policy. You can learn more about this policy on the MDN Web Doc same-origin policy page
You can lern more about this download HTML5 attribute on the MDN Web Doc anchor's attributes page.

Meta tags are not a reliable way to achieve this result. Generally you shouldn't even do this - it should be left up to the user/user agent to decide what do to with the content you provide. The user can always force their browser to download the file if they wish to.
If you still want to force the browser to download the file, modify the HTTP headers directly. Here's a PHP code example:
$path = "path/to/file.pdf";
$filename = "file.pdf";
header('Content-Transfer-Encoding: binary'); // For Gecko browsers mainly
header('Last-Modified: ' . gmdate('D, d M Y H:i:s', filemtime($path)) . ' GMT');
header('Accept-Ranges: bytes'); // Allow support for download resume
header('Content-Length: ' . filesize($path)); // File size
header('Content-Encoding: none');
header('Content-Type: application/pdf'); // Change the mime type if the file is not PDF
header('Content-Disposition: attachment; filename=' . $filename); // Make the browser display the Save As dialog
readfile($path); // This is necessary in order to get it to actually download the file, otherwise it will be 0Kb
Note that this is just an extension to the HTTP protocol; some browsers might ignore it anyway.

I had this same issue and found a solution that has worked great so far. You put the following code in your .htaccess file:
<FilesMatch "\.(?i:pdf)$">
ForceType application/octet-stream
Header set Content-Disposition attachment
</FilesMatch>
It came from Force a File to Download Instead of Showing Up in the Browser.

I found a very simple solution for Firefox (only works with a relative rather than a direct href): add type="application/octet-stream":
Example

Generally it happens, because some browsers settings or plug-ins directly open PDF in the same window like a simple web page.
The following might help you. I have done it in PHP a few years back. But currently I'm not working on that platform.
<?php
if (isset($_GET['file'])) {
$file = $_GET['file'];
if (file_exists($file) && is_readable($file) && preg_match('/\.pdf$/',$file)) {
header('Content-type: application/pdf');
header("Content-Disposition: attachment; filename=\"$file\"");
readfile($file);
}
}
else {
header("HTTP/1.0 404 Not Found");
echo "<h1>Error 404: File Not Found: <br /><em>$file</em></h1>";
}
?>
Save the above as download.php.
Save this little snippet as a PHP file somewhere on your server and you can use it to make a file download in the browser, rather than display directly. If you want to serve files other than PDF, remove or edit line 5.
You can use it like so:
Add the following link to your HTML file.
Download the cool PDF.
Reference from: This blog

Try adding this line to your .htaccess file.
AddType application/octet-stream .pdf
I hope it'll work as it is browser independent.

I just used this, but I don't know if it works across all browsers.
It works in Firefox:
<a href="myfile.pdf" download>Click to Download</a>

A really simple way to achieve this, without using external download sites or modifying headers etc. is to simply create a ZIP file with the PDF inside and link directly to the ZIP file. This will ALWAYS trigger the Save/Open dialog, and it's still easy for people to double-click the PDF windows the program associated with .zip is launched.
BTW great question, I was looking for an answer as well, since most browser-embedded PDF plugins take sooo long to display anything (and will often hang the browser whilst the PDF is loading).

Just put the below code in your .htaccess file:
AddType application/octet-stream .csv
AddType application/octet-stream .xls
AddType application/octet-stream .doc
AddType application/octet-stream .avi
AddType application/octet-stream .mpg
AddType application/octet-stream .mov
AddType application/octet-stream .pdf
Or you can also do trick by JavaScript
element.setAttribute( 'download', whatever_string_you_want);

A very easy way to do this, if you need to force download for a single link on your page, is to use the HTML5 download-attribute in the href-link.
See: http://davidwalsh.name/download-attribute
with this you can rename the file that the user will download and at the same time it forces the download.
There has been a debate whether this is good practice or not, but in my case I have an embedded viewer for a PDF file and the viewer does not offer a download link, so i have to provide one separately. Here I want to make sure the user does not get the PDF opened in the web browser, which would be confusing.
This won't necessary open the save as-dialog, but will download the link straight to the preset download destination. And of course if you are doing a site for someone else, and need them to write in manually attributes to their links is probably a bad idea, but if there is way to get the attribute into the links, this can be a light solution.

A server-side solution is more compatible, until the "download" attribute is implemented in all the browsers.
One Python example could be a custom HTTP request handler for a filestore. The links that point to the filestore are generated like this:
http://www.myfilestore.com/filestore/13/130787e71/download_as/desiredName.pdf
Here is the code:
class HTTPFilestoreHandler(SimpleHTTPRequestHandler):
def __init__(self, fs_path, *args):
self.fs_path = fs_path # Filestore path
SimpleHTTPRequestHandler.__init__(self, *args)
def send_head(self):
# Overwrite SimpleHTTPRequestHandler.send_head to force download name
path = self.path
get_index = (path == '/')
self.log_message("path: %s" % path)
if '/download_as/' in path:
p_parts = path.split('/download_as/')
assert len(p_parts) == 2, 'Bad download link:' + path
path, download_as = p_parts
path = self.translate_path(path )
f = None
if os.path.isdir(path):
if not self.path.endswith('/'):
# Redirect browser - doing basically what Apache does
self.send_response(301)
self.send_header("Location", self.path + "/")
self.end_headers()
return None
else:
return self.list_directory(path)
ctype = self.guess_type(path)
try:
f = open(path, 'rb')
except IOError:
self.send_error(404, "File not found")
return None
self.send_response(200)
self.send_header("Content-type", ctype)
fs = os.fstat(f.fileno())
self.send_header("Expires", '0')
self.send_header("Last-Modified", self.date_time_string(fs.st_mtime))
self.send_header("Cache-Control", 'must-revalidate, post-check=0, pre-check=0')
self.send_header("Content-Transfer-Encoding", 'binary')
if download_as:
self.send_header("Content-Disposition", 'attachment; filename="%s"' % download_as)
self.send_header("Content-Length", str(fs[6]))
self.send_header("Connection", 'close')
self.end_headers()
return f
class HTTPFilestoreServer:
def __init__(self, fs_path, server_address):
def handler(*args):
newHandler = HTTPFilestoreHandler(fs_path, *args)
newHandler.protocol_version = "HTTP/1.0"
self.server = BaseHTTPServer.HTTPServer(server_address, handler)
def serve_forever(self, *args):
self.server.serve_forever(*args)
def start_server(fs_path, ip_address, port):
server_address = (ip_address, port)
httpd = HTTPFilestoreServer(fs_path, server_address)
sa = httpd.server.socket.getsockname()
print "Serving HTTP on", sa[0], "port", sa[1], "..."
httpd.serve_forever()

This is old post but here is the one my solution in JavaScript what using jQuery library.
<script>
(function($){
var download = [];
$('a.force-download, .force-download a').each(function(){
// Collect info
var $this = $(this),
$href = $this.attr('href'),
$split = $href.split('/'),
$name = document.title.replace(/[\W_]/gi, '-').replace(/-{2,}/g, '-'); // get title and clean it for the URL
// Get filename from URL
if($split[($split.length-1)])
{
$tmp = $split[($split.length-1)];
$tmp = $tmp.split('.');
$name = $tmp[0].replace(/[\W_]/gi, '-').replace(/-{2,}/g, '-');
}
// If name already exists, put timestamp there
if($.inArray($name, download) > -1)
{
$name = $name + '-' + Date.now().replace(/[\W]/gi, '-');
}
$(this).attr("download", $name);
download.push($name);
});
}(jQuery || window.jQuery))
</script>
You just need to use class force-download inside your <a> tag and will force download automaticaly. You also can add it to parent div and will pickup all links inside it.
Example:
Download PDF
This is great for WordPress and any other systems or custom websites.

Add a response header Content-Disposition:attachment; followed by the file name. Remove the Meta Content-Disposition;Inline; which will open the document in the same window
In java it is set as
response.setHeader("Content-Disposition", "attachment;filename=test.jpg");

After the file name in the HTML code I add ?forcedownload=1
This has been the simplest way for me to trigger a dialog box to save or download.

If you have a plugin within the browser which knows how to open a PDF file it will open directly. Like in case of images and HTML content.
So the alternative approach is not to send your MIME type in the response. In this way the browser will never know which plugin should open it. Hence it will give you a Save/Open dialog box.

I just had a very similar issue with the added problem that I needed to create download links to files inside a ZIP file.
I first tried to create a temporary file, then provided a link to the temporary file, but I found that some browsers would just display the contents (a CSV Excel file) rather than offering to download. Eventually I found the solution by using a servlet. It works both on Tomcat and GlassFish, and I tried it on Internet Explorer 10 and Chrome.
The servlet takes as input a full path name to the ZIP file, and the name of the file inside the zip that should be downloaded.
Inside my JSP file I have a table displaying all the files inside the zip, with links that say: onclick='download?zip=<%=zip%>&csv=<%=csv%>'
The servlet code is in download.java:
package myServlet;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.zip.*;
import java.util.*;
// Extend HttpServlet class
public class download extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
PrintWriter out = response.getWriter(); // now we can write to the client
String filename = request.getParameter("csv");
String zipfile = request.getParameter("zip");
String aLine = "";
response.setContentType("application/x-download");
response.setHeader( "Content-Disposition", "attachment; filename=" + filename); // Force 'save-as'
ZipFile zip = new ZipFile(zipfile);
for (Enumeration e = zip.entries(); e.hasMoreElements();) {
ZipEntry entry = (ZipEntry) e.nextElement();
if(entry.toString().equals(filename)) {
InputStream is = zip.getInputStream(entry);
BufferedReader br = new BufferedReader(new InputStreamReader(is, "UTF-8"), 65536);
while ((aLine = br.readLine()) != null) {
out.println(aLine);
}
is.close();
break;
}
}
}
}
To compile on Tomcat you need the classpath to include tomcat\lib\servlet-api.jar or on GlassFish: glassfish\lib\j2ee.jar
But either one will work on both. You also need to set your servlet in web.xml.

Chrome 91 had a new change, it supported in chrome 86-90 and 91+.
The following syntax will make it happen.
const fileHandle = await self.showSaveFilePicker({
suggestedName: 'Untitled Text.txt',
types: [{
description: 'Text documents',
accept: {
'text/plain': ['.txt'],
},
}],
});
Read more here:
https://developer.chrome.com/blog/new-in-chrome-91/
**Another solution you can just make it as a blob and then use saveAs **
const blob = fetch("some-url-here").then(data => data.blob());
saveAs(blob, "filename.txt")

With large PDF files the browser hangs.
In Mozilla, menu Tools → Options → Applications, then next to the content type Adobe Acrobat document.
In the Action drop down, select Always ask.
This did not work for me, so what worked was:
Menu Tools* → Add-ons → Adobe Acrobat (Adobe PDF plugin for Firefox) → DISABLE.
Now I am able to download e-books!

Download sharepoint list attachment in IE browser [duplicate]

I have some big size PDF catalogs at my website, and I need to link these as download. When I googled, I found such a thing noted below. It should open the "Save As..." popup at link click...
<head>
<meta name="content-disposition" content="inline; filename=filename.pdf">
...
But it doesn't work :/ When I link to a file as below, it just links to file and is trying to open the file.
File name
UPDATE (according to answers below):
As I see there is no 100% reliable cross-browser solution for this. Probably the best way is using one of the web services listed below, and giving a download link...
http://box.net/
http://droplr.com/
http://getcloudapp.com/

From an answer to Force a browser to save file as after clicking link:
<a href="path/to/file" download>Click here to download</a>

Use the download attribute, but take into account that it only works for files hosted in the same origin that your code. It means that users can only download files that are from the origin site, same host.
Download with original filename:
Click here to download
Download with 'some_name' as filename:
Click here to download
Adding target="_blank" we will use a new Tab instead of the actual one, and also it will contribute to the proper behavior of the download attribute in some scenarios.
It follows the same rules as same-origin policy. You can learn more about this policy on the MDN Web Doc same-origin policy page
You can lern more about this download HTML5 attribute on the MDN Web Doc anchor's attributes page.

Meta tags are not a reliable way to achieve this result. Generally you shouldn't even do this - it should be left up to the user/user agent to decide what do to with the content you provide. The user can always force their browser to download the file if they wish to.
If you still want to force the browser to download the file, modify the HTTP headers directly. Here's a PHP code example:
$path = "path/to/file.pdf";
$filename = "file.pdf";
header('Content-Transfer-Encoding: binary'); // For Gecko browsers mainly
header('Last-Modified: ' . gmdate('D, d M Y H:i:s', filemtime($path)) . ' GMT');
header('Accept-Ranges: bytes'); // Allow support for download resume
header('Content-Length: ' . filesize($path)); // File size
header('Content-Encoding: none');
header('Content-Type: application/pdf'); // Change the mime type if the file is not PDF
header('Content-Disposition: attachment; filename=' . $filename); // Make the browser display the Save As dialog
readfile($path); // This is necessary in order to get it to actually download the file, otherwise it will be 0Kb
Note that this is just an extension to the HTTP protocol; some browsers might ignore it anyway.

I had this same issue and found a solution that has worked great so far. You put the following code in your .htaccess file:
<FilesMatch "\.(?i:pdf)$">
ForceType application/octet-stream
Header set Content-Disposition attachment
</FilesMatch>
It came from Force a File to Download Instead of Showing Up in the Browser.

I found a very simple solution for Firefox (only works with a relative rather than a direct href): add type="application/octet-stream":
Example

Generally it happens, because some browsers settings or plug-ins directly open PDF in the same window like a simple web page.
The following might help you. I have done it in PHP a few years back. But currently I'm not working on that platform.
<?php
if (isset($_GET['file'])) {
$file = $_GET['file'];
if (file_exists($file) && is_readable($file) && preg_match('/\.pdf$/',$file)) {
header('Content-type: application/pdf');
header("Content-Disposition: attachment; filename=\"$file\"");
readfile($file);
}
}
else {
header("HTTP/1.0 404 Not Found");
echo "<h1>Error 404: File Not Found: <br /><em>$file</em></h1>";
}
?>
Save the above as download.php.
Save this little snippet as a PHP file somewhere on your server and you can use it to make a file download in the browser, rather than display directly. If you want to serve files other than PDF, remove or edit line 5.
You can use it like so:
Add the following link to your HTML file.
Download the cool PDF.
Reference from: This blog

Try adding this line to your .htaccess file.
AddType application/octet-stream .pdf
I hope it'll work as it is browser independent.

I just used this, but I don't know if it works across all browsers.
It works in Firefox:
<a href="myfile.pdf" download>Click to Download</a>

A really simple way to achieve this, without using external download sites or modifying headers etc. is to simply create a ZIP file with the PDF inside and link directly to the ZIP file. This will ALWAYS trigger the Save/Open dialog, and it's still easy for people to double-click the PDF windows the program associated with .zip is launched.
BTW great question, I was looking for an answer as well, since most browser-embedded PDF plugins take sooo long to display anything (and will often hang the browser whilst the PDF is loading).

Just put the below code in your .htaccess file:
AddType application/octet-stream .csv
AddType application/octet-stream .xls
AddType application/octet-stream .doc
AddType application/octet-stream .avi
AddType application/octet-stream .mpg
AddType application/octet-stream .mov
AddType application/octet-stream .pdf
Or you can also do trick by JavaScript
element.setAttribute( 'download', whatever_string_you_want);

A very easy way to do this, if you need to force download for a single link on your page, is to use the HTML5 download-attribute in the href-link.
See: http://davidwalsh.name/download-attribute
with this you can rename the file that the user will download and at the same time it forces the download.
There has been a debate whether this is good practice or not, but in my case I have an embedded viewer for a PDF file and the viewer does not offer a download link, so i have to provide one separately. Here I want to make sure the user does not get the PDF opened in the web browser, which would be confusing.
This won't necessary open the save as-dialog, but will download the link straight to the preset download destination. And of course if you are doing a site for someone else, and need them to write in manually attributes to their links is probably a bad idea, but if there is way to get the attribute into the links, this can be a light solution.

A server-side solution is more compatible, until the "download" attribute is implemented in all the browsers.
One Python example could be a custom HTTP request handler for a filestore. The links that point to the filestore are generated like this:
http://www.myfilestore.com/filestore/13/130787e71/download_as/desiredName.pdf
Here is the code:
class HTTPFilestoreHandler(SimpleHTTPRequestHandler):
def __init__(self, fs_path, *args):
self.fs_path = fs_path # Filestore path
SimpleHTTPRequestHandler.__init__(self, *args)
def send_head(self):
# Overwrite SimpleHTTPRequestHandler.send_head to force download name
path = self.path
get_index = (path == '/')
self.log_message("path: %s" % path)
if '/download_as/' in path:
p_parts = path.split('/download_as/')
assert len(p_parts) == 2, 'Bad download link:' + path
path, download_as = p_parts
path = self.translate_path(path )
f = None
if os.path.isdir(path):
if not self.path.endswith('/'):
# Redirect browser - doing basically what Apache does
self.send_response(301)
self.send_header("Location", self.path + "/")
self.end_headers()
return None
else:
return self.list_directory(path)
ctype = self.guess_type(path)
try:
f = open(path, 'rb')
except IOError:
self.send_error(404, "File not found")
return None
self.send_response(200)
self.send_header("Content-type", ctype)
fs = os.fstat(f.fileno())
self.send_header("Expires", '0')
self.send_header("Last-Modified", self.date_time_string(fs.st_mtime))
self.send_header("Cache-Control", 'must-revalidate, post-check=0, pre-check=0')
self.send_header("Content-Transfer-Encoding", 'binary')
if download_as:
self.send_header("Content-Disposition", 'attachment; filename="%s"' % download_as)
self.send_header("Content-Length", str(fs[6]))
self.send_header("Connection", 'close')
self.end_headers()
return f
class HTTPFilestoreServer:
def __init__(self, fs_path, server_address):
def handler(*args):
newHandler = HTTPFilestoreHandler(fs_path, *args)
newHandler.protocol_version = "HTTP/1.0"
self.server = BaseHTTPServer.HTTPServer(server_address, handler)
def serve_forever(self, *args):
self.server.serve_forever(*args)
def start_server(fs_path, ip_address, port):
server_address = (ip_address, port)
httpd = HTTPFilestoreServer(fs_path, server_address)
sa = httpd.server.socket.getsockname()
print "Serving HTTP on", sa[0], "port", sa[1], "..."
httpd.serve_forever()

This is old post but here is the one my solution in JavaScript what using jQuery library.
<script>
(function($){
var download = [];
$('a.force-download, .force-download a').each(function(){
// Collect info
var $this = $(this),
$href = $this.attr('href'),
$split = $href.split('/'),
$name = document.title.replace(/[\W_]/gi, '-').replace(/-{2,}/g, '-'); // get title and clean it for the URL
// Get filename from URL
if($split[($split.length-1)])
{
$tmp = $split[($split.length-1)];
$tmp = $tmp.split('.');
$name = $tmp[0].replace(/[\W_]/gi, '-').replace(/-{2,}/g, '-');
}
// If name already exists, put timestamp there
if($.inArray($name, download) > -1)
{
$name = $name + '-' + Date.now().replace(/[\W]/gi, '-');
}
$(this).attr("download", $name);
download.push($name);
});
}(jQuery || window.jQuery))
</script>
You just need to use class force-download inside your <a> tag and will force download automaticaly. You also can add it to parent div and will pickup all links inside it.
Example:
Download PDF
This is great for WordPress and any other systems or custom websites.

Add a response header Content-Disposition:attachment; followed by the file name. Remove the Meta Content-Disposition;Inline; which will open the document in the same window
In java it is set as
response.setHeader("Content-Disposition", "attachment;filename=test.jpg");

After the file name in the HTML code I add ?forcedownload=1
This has been the simplest way for me to trigger a dialog box to save or download.

If you have a plugin within the browser which knows how to open a PDF file it will open directly. Like in case of images and HTML content.
So the alternative approach is not to send your MIME type in the response. In this way the browser will never know which plugin should open it. Hence it will give you a Save/Open dialog box.

I just had a very similar issue with the added problem that I needed to create download links to files inside a ZIP file.
I first tried to create a temporary file, then provided a link to the temporary file, but I found that some browsers would just display the contents (a CSV Excel file) rather than offering to download. Eventually I found the solution by using a servlet. It works both on Tomcat and GlassFish, and I tried it on Internet Explorer 10 and Chrome.
The servlet takes as input a full path name to the ZIP file, and the name of the file inside the zip that should be downloaded.
Inside my JSP file I have a table displaying all the files inside the zip, with links that say: onclick='download?zip=<%=zip%>&csv=<%=csv%>'
The servlet code is in download.java:
package myServlet;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.zip.*;
import java.util.*;
// Extend HttpServlet class
public class download extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
PrintWriter out = response.getWriter(); // now we can write to the client
String filename = request.getParameter("csv");
String zipfile = request.getParameter("zip");
String aLine = "";
response.setContentType("application/x-download");
response.setHeader( "Content-Disposition", "attachment; filename=" + filename); // Force 'save-as'
ZipFile zip = new ZipFile(zipfile);
for (Enumeration e = zip.entries(); e.hasMoreElements();) {
ZipEntry entry = (ZipEntry) e.nextElement();
if(entry.toString().equals(filename)) {
InputStream is = zip.getInputStream(entry);
BufferedReader br = new BufferedReader(new InputStreamReader(is, "UTF-8"), 65536);
while ((aLine = br.readLine()) != null) {
out.println(aLine);
}
is.close();
break;
}
}
}
}
To compile on Tomcat you need the classpath to include tomcat\lib\servlet-api.jar or on GlassFish: glassfish\lib\j2ee.jar
But either one will work on both. You also need to set your servlet in web.xml.

Chrome 91 had a new change, it supported in chrome 86-90 and 91+.
The following syntax will make it happen.
const fileHandle = await self.showSaveFilePicker({
suggestedName: 'Untitled Text.txt',
types: [{
description: 'Text documents',
accept: {
'text/plain': ['.txt'],
},
}],
});
Read more here:
https://developer.chrome.com/blog/new-in-chrome-91/
**Another solution you can just make it as a blob and then use saveAs **
const blob = fetch("some-url-here").then(data => data.blob());
saveAs(blob, "filename.txt")

With large PDF files the browser hangs.
In Mozilla, menu Tools → Options → Applications, then next to the content type Adobe Acrobat document.
In the Action drop down, select Always ask.
This did not work for me, so what worked was:
Menu Tools* → Add-ons → Adobe Acrobat (Adobe PDF plugin for Firefox) → DISABLE.
Now I am able to download e-books!

php://stdin reading extra characters

I am having a weird problem with a system that I am making. I am attempting to create a system to upload files to a server. I do not have direct file write privileges, and HTTP POST multipart/form-data file uploads do not work. I unfortunately do not have direct access to the server.
My solution is to use jQuery's $.ajax function to upload the file via HTTP PUT, then read it in from STDIN in PHP on the server, and upload the contents to a different location via FTP.
Everything appears to work, however somewhere along the line, extra bytes are being added. On the client, Windows claims that the file (I am testing with my website's favicon.ico file) is 7358 bytes. Once I read in the file using a standard Javascript FileReader object, it appears to be only 7311 bytes. Then, I successfully PUT it to a PHP script on the server, which claims that it read 10890 bytes, which FileZilla agrees with when I check the dump folder over FTP.
Here is my Javascript code to upload (jQuery 1.11.3 is included, and file_input is <input type="file" id="file_input"/>:
function upload(){
console.log("upload");
var f = file_input.files[0];
var r = new FileReader();
r.onload = function(event){
var d = r.result;
console.log("data loaded");
console.log(d.length);
$.ajax({
url: "upload.php?name="+encodeURIComponent(f.name)+"&mime="+encodeURIComponent(f.mime),
context: document.body,
method: "PUT",
contentType: "application/octet-stream",
data: d
}).done(function(data){
console.log("done");
console.log(data);
});
};
r.onerror = function(event){
alert("ERROR READING FILE!\nCode " + event.target.error.code);
};
r.readAsText(f);
console.log("initiated");
}
As you can see, the name and MIME type are included via the GET query string.
Here is my PHP that accepts the upload (part of upload.php):
if(strtoupper($_SERVER['REQUEST_METHOD'])=="PUT"){
echo "uploading\n";
echo "connected\n";
var_dump($_POST);
echo "x";
$file=fopen("php://input","r");
var_dump($file);
$x="";
while($byte=fgetc($file)!==false){
$x.=$byte;
}
echo strlen($x);
echo "\n";
$ftp=fopen('ftp://user:pass#example.com/admin/fs/upload/'.uniqid('',true),'w');
var_dump($ftp);
fwrite($ftp,$x);
fclose($ftp);
echo "done\n";
}
I examined the files in notepad, and the majority of the file appeared to be unchanged (there weren't any HTTP headers or anything), however the new file refused to open in any image viewer (the original would). Based on the differences in the files - only some parts are changes, and they are changed to what appear to be random non-visual characters - I would guess that it has something to do with a character encoding discrepancy. Any ideas would be appreciated.
Thanks,
MagikM18
EDIT
My server is Apache/2.4.6 and running on x86_64-redhat-linux-gnu (according to phpinfo()).
Also, I tested it with a text-based file (a PHP script) and it worked just fine - it must be something to do with the file's binary content.

For binary files (i.e. ain't text), you can try appending b to the flags of fopen:
fopen("php://input","rb");
/*
...
*/
$ftp=fopen('ftp://user:pass#example.com/admin/fs/upload/'.uniqid('',true),'wb');
Edit
You have to send files as binary too, in addition to receiving the stream. See the link in comments.

How to cache JavaScript files in Internet Explorer? [duplicate]

Which is the best method to make the browser use cached versions of js files (from the serverside)?

Have a look at Yahoo! tips: https://developer.yahoo.com/performance/rules.html#expires.
There are also tips by Google: https://developers.google.com/speed/docs/insights/LeverageBrowserCaching

or in the .htaccess file
AddOutputFilter DEFLATE css js
ExpiresActive On
ExpiresByType application/x-javascript A2592000

I just finished my weekend project cached-webpgr.js
which uses the localStorage / web storage to cache JavaScript files. This approach is very fast. My small test showed
Loading jQuery from CDN: Chrome 268ms, FireFox: 200ms
Loading jQuery from localStorage: Chrome 47ms, FireFox 14ms
The code to achieve that is tiny, you can check it out at my Github project https://github.com/webpgr/cached-webpgr.js
Here is a full example how to use it.
The complete library:
function _cacheScript(c,d,e){var a=new XMLHttpRequest;a.onreadystatechange=function(){4==a.readyState&&(200==a.status?localStorage.setItem(c,JSON.stringify({content:a.responseText,version:d})):console.warn("error loading "+e))};a.open("GET",e,!0);a.send()}function _loadScript(c,d,e,a){var b=document.createElement("script");b.readyState?b.onreadystatechange=function(){if("loaded"==b.readyState||"complete"==b.readyState)b.onreadystatechange=null,_cacheScript(d,e,c),a&&a()}:b.onload=function(){_cacheScript(d,e,c);a&&a()};b.setAttribute("src",c);document.getElementsByTagName("head")[0].appendChild(b)}function _injectScript(c,d,e,a){var b=document.createElement("script");b.type="text/javascript";c=JSON.parse(c);var f=document.createTextNode(c.content);b.appendChild(f);document.getElementsByTagName("head")[0].appendChild(b);c.version!=e&&localStorage.removeItem(d);a&&a()}function requireScript(c,d,e,a){var b=localStorage.getItem(c);null==b?_loadScript(e,c,d,a):_injectScript(b,c,d,a)};
Calling the library
requireScript('jquery', '1.11.2', 'http://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js', function(){
requireScript('examplejs', '0.0.3', 'example.js');
});

From PHP:
function OutputJs($Content)
{
ob_start();
echo $Content;
$expires = DAY_IN_S; // 60 * 60 * 24 ... defined elsewhere
header("Content-type: x-javascript");
header('Content-Length: ' . ob_get_length());
header('Cache-Control: max-age='.$expires.', must-revalidate');
header('Pragma: public');
header('Expires: '. gmdate('D, d M Y H:i:s', time()+$expires).'GMT');
ob_end_flush();
return;
}
works for me.
As a developer you'll probably quickly run into the situation that you don't want files cached, in which case see Help with aggressive JavaScript caching

In your Apache .htaccess file:
#Create filter to match files you want to cache
<Files *.js>
Header add "Cache-Control" "max-age=604800"
</Files>
I wrote about it here also:
http://betterexplained.com/articles/how-to-optimize-your-site-with-http-caching/

I am heavily tempted to close this as a duplicate; this question appears to be answered in many different ways all over the site:
will a script in html's script tag with extension php be cached?
When does browser automatically clear cache of external JavaScript file?
Help with aggressive JavaScript caching
How to control web page caching, across all browsers?
How can I make the browser see CSS and Javascript changes?

The best (and only) method is to set correct HTTP headers, specifically these ones: "Expires", "Last-Modified", and "Cache-Control". How to do it depends on the server software you use.
In Improving performance… look for "Optimization on server side" for general considerations and relevant links and for "Client-side cache" for the Apache-specific advice.
If you are a fan of nginx (or nginx in plain English) like I am, you can easily configure it too:
location /images {
...
expires 4h;
}
In the example above any file from /images/ will be cached on the client for 4 hours.
Now when you know right words to look for (HTTP headers "Expires", "Last-Modified", and "Cache-Control"), just peruse the documentation of the web server you use.

I have a simple system that is pure JavaScript. It checks for changes in a simple text file that is never cached. When you upload a new version this file is changed. Just put the following JS at the top of the page.
(function(url, storageName) {
var fromStorage = localStorage.getItem(storageName);
var fullUrl = url + "?rand=" + (Math.floor(Math.random() * 100000000));
getUrl(function(fromUrl) {
// first load
if (!fromStorage) {
localStorage.setItem(storageName, fromUrl);
return;
}
// old file
if (fromStorage === fromUrl) {
return;
}
// files updated
localStorage.setItem(storageName, fromUrl);
location.reload(true);
});
function getUrl(fn) {
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET", fullUrl, true);
xmlhttp.send();
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState === XMLHttpRequest.DONE) {
if (xmlhttp.status === 200 || xmlhttp.status === 2) {
fn(xmlhttp.responseText);
}
else if (xmlhttp.status === 400) {
throw 'unable to load file for cache check ' + url;
}
else {
throw 'unable to load file for cache check ' + url;
}
}
};
}
;
})("version.txt", "version");
just replace the "version.txt" with your file that is always run and "version" with the name you want to use for your local storage.

How do I prompt user to save text (xml) to a file?

I've have some javascript code that transforms XML with XSLT. I now want the user to be able to save that new XML (either by prompting them or throwing the new XML up as a file or something so that the user can then save it. Anybody know how to do that?
var xmldoc = new ActiveXObject("Microsoft.XMLDOM");
xmldoc.async = false;
xmldoc.loadXML(responseText); // responseText is xml returned from ajax call
//apply the xslt
var xsldoc = new ActiveXObject("Microsoft.XMLDOM");
xsldoc.async = false;
xsldoc.load("../xslt/ExtraWorkRequest.xslt");
var content = xmldoc.transformNode(xsldoc);
How do I get the user to save the XML (content) as a file?

By default, you can't. Browser isn't supposed to access your local disks for security reasons.
But, if you can ask your user to change it's security settings (and you should not to ask), you can to use FileSystemObject or even your Microsoft.XMLDOM.Save method.

You cannot do it with 100% client-side JavaScript with the default security settings. You'll need to implement some server-side logic. In your case, you'll be able to do the XML transformation server-side, as well.
http://www.bigresource.com/Tracker/Track-javascripts-ijfTJlI9/
http://support.microsoft.com/kb/q260519/

You could construct a data: URI with a media type of application/octet-stream.
function download (data, charset) {
if (!charset) {
charset = document.characterSet;
}
location.href = ["data:application/octet-stream;charset=",
charset, ",", encodeURIComponent(data)
].join("");
}
All browsers except IE support data: URIs. I think IE8 may support them, but only for images. For IE, a workaround could be to send the data to a server (including document.characterSet) and then load a page that has something like the following header:
Content-Type: application/xml; charset={document.characterSet}
Content-Disposition: attachment
If you want to give the file a name too, use Content-Disposition: attachment; filename=....
Also, for any of this to work, you have to convert your XML to a string first.

I do this with code snippets on my blog (user can click on the save button, and the snippet will come up in their default text editor, where they can tweak it and/or copy it into their app).
It works by putting all the textual data inside of a hidden field, and then submits it to a very simple server-side HTTP handler. The handler just grabs the hidden field value and spits it right back out in the response with the right content-disposition header, giving the user the open/save download prompt.
This is the only way I could get it to work.

Develop Reference

JavaScript is the programming language of the Web.