Develop Reference

Generate and download archive zip with java

I have a zip file download function.
This function generates the .zip files on output folder in the server and downloads it.
Everything works perfectly!
However, testing with multi-users doens't work.
If 3 users attempt to generate the file at the same time, only one response is returned with the file for download.
The other 2 users are waiting forever and there is no result (no error occurs, the ajax call never returns).
My code:
JavaScript:
$.fileDownload('\GenereteZipAction', {
httpMethod: "POST",
data: $('#formZip').serialize()
}).done(function () {
alert('Download successfully.');
$('#modalZipLoading').modal('hide');
})
.fail(function () {
alert('Error');
$('#modalZipLoading').modal('hide');
});
Java:
//get the name of user
userName = request.getParameter("user");
//get real path
String realPath = getServletContext().getRealPath("/");
//create user folder
File fileOutput = new File(realPath+"/reports/output/"+userName);
fileOutput.mkdirs();
//generete reports in the user output folder
ReportHelper helper = new ReportHelper();
helper.genereteReports(fileOutput);
//set the reponse and...
response.setContentType("application/zip");
response.addHeader("Content-Disposition", "attachment;filename=Relatorios.zip");
//set the cookie for $.fileDownload go to done function
response.setHeader("Set-Cookie", "fileDownload=true; path=/");
//zip output user folder
ZipHelper zipHelper = new ZipHelper ();
zipHelper.zipAllfiles(fileOutput);
//create and fill ZipOutputStream
ZipOutputStream zip = new ZipOutputStream(response.getOutputStream());
zipHelper.fillZipOutputStream(zip);
//do download
zip.flush();
//close
zip.close();
//delete folder
deleteDir(fileOutput);
My system is for more than five thousand users, so I'm sure more than two will use the report generation function at the same time.
I do not have much information of aplication server, just know it is IBM WebSphere.
I do not know if the problem is in my code, or the server that
not allowing multi-users. Every help is welcome!!!

You are most likely running into thread safety issues. This may help you: https://www.quora.com/What-does-the-term-thread-safe-mean-in-Java
ReportHelper or ZipHelper could be not thread-safe. genereteReports looks to be modifying something on the file system. I would look carefully at the code and ask yourself on each line, "what happens if something else tries to execute while my first thread is executing this line?" I would suggest looking into synchronized calls and how they work.

How do I return a file to the user?

I am trying to return a file to the user.
"GetExcel" appears to work and in debug I can see that "ba" has data.
The method completes BUT nothing appears to be returned to the browser - I am hoping to see the file download dialog.
C#
public FileResult GetExcel()
{
using (ExcelPackage pck = new ExcelPackage())
{
ExcelWorksheet ws = pck.Workbook.Worksheets.Add("Demo");
ws.Cells["A1"].Value = "LBHERE";
var ba = pck.GetAsByteArray();
return File(ba, "text/plain", "testFile.txt");
}
}
Javascript
function clickedTest() {
alert("Test clicked");
$.get(myPath + "/Employee/GetExcel", { }, function (data) {
})
};

jQuery's $.get() function pulls data from a webpage into your client-side scripts through AJAX. This is not what you want to do if you want to download a file. Instead, you should open a new tab set to the URL of the file you wish to download.
Try this:
function clickedTest() {
window.open(myPath + "/Employee/GetExcel", "_blank");
}
If your browser still isn't initiating a download, but is instead just displaying a file, you may have to go one step further.
Somewhere in your server-side code, when you have access to the Response object, you should set the Content-Disposition header to attachment and provide a filename for the spreadsheet you are serving. This will inform your browser that the file you are requesting is meant to be downloaded, not displayed.
This can be done as follows:
Response.AddHeader("Content-Disposition", "attachment;filename=myfile.xls")
Of course, replace myfile.xls with the proper filename for your spreadsheet.

Why doesn't Microsoft Skydrive download multiple files even though MS example shows it? (wl.download)

Summary
I am attempting to find out why the wl.download function will not download more than one file even though the Microsoft examples seem to indicate that they can.
And, the code seems to be called for each file you attempt to download, but only the one file is actually downloaded.
Details
Here are the details of how you can see this problem which I've tried in IE 11.x and Chrome 30.x
If you will kindly go to :
http://isdk.dev.live.com/dev/isdk/ISDK.aspx?category=scenarioGroup_skyDrive&index=0
You will be able to run an example app which allows you to download files from your skydrive.
Note: the app does require you to allow the app to access your skydrive.
Once you get there you'll see code that looks like this on the right side of the page:
Alter One Value: select:
You need to alter one value: Change the
select: 'single'
to
select: 'multi'
which will allow you to select numerous files to download to your computer. If you do not make that one change then you won't be able to choose more than one file in the File dialog.
Click the Run Button to Start
Next, you'll see a [Run] button to start the app (above the code sample).
Go ahead and click that button.
Pick Files For Download
After that just traverse through your skydrive files and choose more than one in a folder and click the [Open] button. At that point, you will see one of the files actually downloads, and a number of file names are displayed in the bottom (output) section of the example web page.
My Questions
Why is it that the others do not download, even though wl.download is called in the loop, just as the console.log is called in the loop?
Is this a known limitation of the browser?
Is this a known bug in skydrive API?
Is this just a bug in the example code?

The problem here is that the call to wl.download({ "path": file.id + "/content" }) stores some internal state (among other things, the file being downloaded and the current status thereof). By looping over the list of files, that state is in fact overwritten with each call. When I tried downloading three text files at once, it was always the last one that was actually downloaded and never the first two.
The difficulty here is that the downloads are executed in the traditional fashion, whereby the server adds Content-Disposition: attachment to the response headers to force the browser to download the file. Because of this, it is not possible to receive notification of any kind when the download has actually completed, meaning that you can't perform the downloads serially to get around the state problem.
One approach that I thought might work is inspired by this question. According to the documentation, we can get a download link to a file if we append /content?suppress_redirects=true to its id. Using this approach, we can set the src property of an IFrame and download the file that way. This works OK, but it will only force a download for file types that the browser can't natively display (zip files, Exe files, etc.) due to the lack of the Content-Disposition: attachment response header.
The following is what I used in the Interactive Live SDK.
WL.init({ client_id: clientId, redirect_uri: redirectUri });
WL.login({ "scope": "wl.skydrive wl.signin" }).then(
function(response) {
openFromSkyDrive();
},
function(response) {
log("Failed to authenticate.");
}
);
function openFromSkyDrive() {
WL.fileDialog({
mode: 'open',
select: 'multi'
}).then(
function(response) {
log("The following file is being downloaded:");
log("");
var files = response.data.files;
for (var i = 0; i < files.length; i++) {
var file = files[i];
log(file.name);
WL.api({
path: file.id + "/content?suppress_redirects=true",
method: "GET"
}).then(
function (response) {
var iframe = document.createElement("iframe");
iframe.src = response.location;
iframe.style.display = "none";
document.body.appendChild(iframe);
},
function (responseFailed) {
log("Error calling API: " + responseFailed.error.message);
}
);
}
},
function(errorResponse) {
log("WL.fileDialog errorResponse = " + JSON.stringify(errorResponse));
}
);
}
function log(message) {
var child = document.createTextNode(message);
var parent = document.getElementById('JsOutputDiv') || document.body;
parent.appendChild(child);
parent.appendChild(document.createElement("br"));
}

Did you try to bind some events to the WL.download() method? According to the documentation:
The WL.download method accepts only one parameter:
The required path parameter specifies the unique SkyDrive file ID of the file to download.
If the WL.download method call is unsuccessful, you can use its then method's onError parameter to report the error. In this case, the WL.download doesn't support the onSuccess and onProgress parameters. If the WL.download method call is successful, the user experience for actually downloading the files will differ based on the type of web browser in use.
Perhaps you are getting some errors in your log to identify the problem.
For me, one suggestion without having checked the documentation, I can think of the fact that you are not waiting for each download to end. Why not change your loop in such a manner that you call WL.download() only if you know no other download is currently running ( like calling the next WL.download only in the success/complete event ):
WL.download({ "path": file.id + "/content" }).then(
function (response) {
window.console && console.log("File downloaded.");
//call the next WL.download() here <!-----------------
},
function (responseFailed) {
window.console && console.log( "Error downloading file: " + responseFailed.error.message);
}
);

Change html page content

I am creating Firefox addon using the Add-on SDK. I want to get data from remote url and inject it in current html. As of now i m able to fetch data using request module of Firefox addon sdk but m not able to inject it in current page.
for example : i am fetching response from website "abc.com".after fetching response i will augment current page with response
// main.js
var widgets = require("sdk/widget");
var tabs = require("sdk/tabs");
var Request = require("sdk/request").Request;
//create addon widget
var widget = widgets.Widget({
id: "div-show",
label: "Show divs",
contentURL: "http://www.mozilla.org/favicon.ico",
onClick: function() {
//initializing request module to fetch content
quijote.get();
}
});
//fetch content of requested page
var quijote = Request({
url: "http://localhost/abc/",
overrideMimeType: "text/plain; charset=latin1",
onComplete: function (response) {
//check if content is fetched successfully
addContent(response);
}
});
//try and modify current page
function addContent(response){
//initialize page modification module
var pageMod = require("sdk/page-mod");
tabs.activeTab.attach({
contentScript: 'document.body.innerHTML = ' + ' "<h1>'+response.text+'</h1>";'
});
}
Is their any way in which i can augment my current page???

Your code will bitterly fail e.g. when response.text includes a double quote.
Then your code would be (assume it is world):
document.body.innerHTML = "<h1>world</h1>";
This is obviously invalid code.
Your code basically constructs a dynamic script from unsanitized data, which is a bad idea because (other than the escaping problem above)
you'll be running an unsanitized content script if that code is even valid and
if that would succeed, the page might run unsanitized code as well.
This is the web equivalent to SQL injection attacks....
First, lets tackle 1.) with messaging (more):
var worker = tabs.activeTab.attach({
contentScript: 'self.port.on("setdom", function(data) { ' +
+ 'document.body.innerHTML = data; /* still a security issue! */'
+ '});'
});
worker.port.emit("setdom", response.text);
This guarantees that the content script will be valid (can even run) and does not run arbitrary code.
However 2.) is still a problem. Read DOM Building and HTML insertion.

Is robust javascript-only upload of file possible

I want a robust way to upload a file. That means that I want to be able to handle interruptions, error and pauses.
So my question is: Is something like the following possible using javascript only on the client.
If so I would like pointers to libraries, tutorials, books or implementations.
If not I would like an explanation to why it's not possible.
Scenario:
Open a large file
Split it into parts
For each part I would like to
Create checksum and append to data
Post data to server (the server would check if data uploaded correctly)
Check a web page on server to see if upload is ok
If yes upload next part if no retry
Assume all posts to server is accompanied by relevant meta data (sessionid and whatnot).

No. You can, through a certain amount of hackery, begin a file upload with AJAX, in which case you'll be able to tell when it's finished uploading. That's it.
JavaScript does not have any direct access to files on the visitor's computer for security reasons. The most you'll be able to see from within your script is the filename.

Firefox 3.5 adds support for DOM progress event monitoring of XMLHttpRequest transfers which allow you to keep track of at least upload status as well as completion and cancellation of uploads.
It's also possible to simulate progress tracking with iframes in clients that don't support this newer XMLHTTPRequest additions.
For an example of script that does just this, take a look at NoSWFUpload. I've been using it succesfully for about few months now.

It's possible in Firefox 3 to open a local file as chosen by a file upload field and read it into a JavaScript variable using the field's files array. That would allow you to do your own chunking, hashing and sending by AJAX.
There is some talk of getting something like this standardised by W3, but for the immediate future no other browser supports this.

Yes. Please look at the following file -
function Upload() {
var self = this;
this.btnUpload;
this.frmUpload;
this.inputFile;
this.divUploadArea;
this.upload = function(event, target) {
event.stopPropagation();
if (!$('.upload-button').length) {
return false;
}
if (!$('.form').length) {
return false;
}
self.btnUpload = target;
self.frmUpload = $(self.btnUpload).parents('form:first');
self.inputFile = $(self.btnUpload).prev('.upload-input');
self.divUploadArea = $(self.btnUpload).next('.uploaded-area');
var target = $(self.frmUpload).attr('target');
var action = $(self.frmUpload).attr('action');
$(self.frmUpload).attr('target', 'upload_target'); //change the form's target to the iframe's id
$(self.frmUpload).attr('action', '/trnUpload/upload'); //change the form's action to the upload iframe function page
$(self.frmUpload).parent("div").prepend(self.iframe);
$('#upload_target').load(function(event){
if (!$("#upload_target").contents().find('.upload-success:first').length) {
$('#upload_target').remove();
return false;
} else if($("#upload_target").contents().find('.upload-success:first') == 'false') {
$('#upload_target').remove();
return false;
}
var fid = $("#upload_target").contents().find('.fid:first').html();
var filename = $("#upload_target").contents().find('.filename:first').html();
var filetype = $("#upload_target").contents().find('.filetype:first').html();
var filesize = $("#upload_target").contents().find('.filesize:first').html();
$(self.frmUpload).attr('target', target); //change the form's target to the iframe's id
$(self.frmUpload).attr('action', action); //change the form's
$('#upload_target').remove();
self.insertUploadLink(fid, filename, filetype, filesize);
});
};
this.iframe = '' +
'false' +
'';
this.insertUploadLink = function (fid, filename, filetype, filesize) {
$('#upload-value').attr('value', fid);
}
}
$(document).ready(event) {
var myupload = new Upload();
myupload.upload(event, event.target);
}
With also using PHP's APC to query the status of how much of the file has been uploaded, you can do a progress bar with a periodical updater (I would use jQuery, which the above class requires also). You can use PHP to output both the periodical results, and the results of the upload in the iframe that is temporarily created.
This is hackish. You will need to spend a lot of time to get it to work. You will need admin access to whatever server you want to run it on so you can install APC. You will also need to setup the HTML form to correspond to the js Upload class. A reference on how to do this can be found here http://www.ultramegatech.com/blog/2008/12/creating-upload-progress-bar-php/