I want to upload ajax file upload which uses xhr to send file data,
at client m using this
http://valums.com/ajax-upload/
how i will accept this data on node and save the file to server by node.js , which module i need to use in node.js?
I've created an uploader with progress bar using the formidable module, it's really easy to use and provides a lot of useful callbacks.
Have a look here:
https://github.com/felixge/node-formidable (scroll down to get the Docs)
http://debuggable.com/posts/parsing-file-uploads-at-500-mb-s-with-node-js:4c03862e-351c-4faa-bb67-4365cbdd56cb
due to the lack of an example file in valums ajax-uploader, I've just created one.
It catches up the XHR upload if possible, alternatively falling back to the old form-based method.
All in conclusion to valums ajax-uploader.
https://github.com/aldipower/file-uploader/blob/master/server/nodejs.js
Maybe Valums will accept the pull request some time and the sample file gets merged in the standard repository.
Related
Our application is entirely built on websockets. We don't do any HTTP request-reply. However, we are stuck with file download. If i receive file content via websockets can I wrote to local folder on user computer ?
If it makes a difference, we are only supporting Chrome so not issue if it doesn't work on other browsers.
Also, I know i can do this via HTTP. Trying to avoid it and stick to websockets since thats how the entire app is.
Thanks a lot in advance!
The solution depends on size of your file.
If size is less than about 50 MB, I would encode file's content to base64 string on the server and send this string to the client. Client should receive parts of the string, concat them to single result, and store. After receiving whole string, add link (tag <a>) to your page with attribute href set to "data:<data_type>;base64,<base64_encoded_file_content>". <data_type> is a mime type of your file, for example "text/html" or "image/png". Suggest file name by adding download attribute set to name of file (doesn't work for Chrome on OS X).
Unfortunately I have no solution for large files. Currently there is only FileEntry API that allows to write files with JS, but according to documentation it is supported only by Chrome v13+, learn more here https://developer.mozilla.org/en-US/docs/Web/API/FileEntry.
I know how to use JSON in dart also communicating with a server using the HttpRequest API from the dart:html library and parsing JSON data using the dart:convert !!https://www.dartlang.org/articles/json-web-service/
I am looking for Dynamic content loading using Ajax asynchronous methods or calls in DART! ..
like .. the web page need to load content dynamically if there is any change or update in JSON files in server! ..
And how to do this in Angular Dart!?
There's no way to be notified when something changes on the server without either a) polling for changes (this can be pretty wasteful) or b) having the server notify you.
For (a), you could create a periodic timer that fetches the JSON or checks whether it's been updated (you'd need some way of checking this with the server).
A better fit would be something like Web Sockets, with the server able to push your JSON to the client whenever it changes. However, this is quite an architecture change from pulling JSON from the server, because you would need to be holding web sockets open between the server and all clients that have the page loaded, so the server can send the data to them all whenever it changes.
There are some samples of using Web Sockets on the Dart site; but bear in mind you'll need something on the server, this won't work if you only have access to the client.
Im currently writing a small Docpad plugin to output a documents contentRenderedWithoutLayouts into a separate .json file next to the .html version for loading it via an ajax request later.
The plugin works by overriding Baseplugin's render: (opts) -> method and doing a few checks whether we're rendering a document and to html.
I now noticed that this method gets called multiple times for some documents, which seems to be render pass related. So how can I detect the final render pass per document to avoid writing the .json multiple times per render?
Many Thanks
--
Edit:
found the answer after another look at Docpads events list: http://docpad.org/docs/events
The writeAfter event is the right place to get the final data and have the output directory tree set up so I can put my .json files next to the .html.
In case you're interested find the plugin here: https://github.com/field/docpad-plugin-jsonfragment
Another approach to this would be to use the serverExtend event, and write a router that detects if it is an ajax request (existance of the IS_XHR header) and then sends the necessary json data from that. This would require your hosting platform to support node.js as you'll be using the docpad server.
I'm new and just developing on J2EE.
I am modifying an existing application (an OpenSource project).
I need to save an image on a client sent by the server, but I do not know how.
This activity must be done in a transparent manner without affecting the existing operation of the application.
From the tests done I get this error:
java.lang.IllegalStateException: getWriter () has Already Been Called for this response.
How should carry out this task, according to your own opinion?
How do I save on the client, locally, the image?
Update:
Thanks for the answers.
My problem is that:
the image is generated on the server, but not for direct client request (there is no link to click on web page), the picture is composed using other services on the Internet.
reconstruct the image on the server.
This image must be sent to the client to be saved locally.
so I'd like it to appear a window where you assign the destination image
plus I'd like the rest of the application were not affected by this activity.
The application is yet on production.
Thank you very much for your response.
From the tests done I get this error: java.lang.IllegalStateException: getWriter () has Already Been Called for this response.
In other words, you were trying to mix the binary data of the image with the character data of the HTML output, or you were trying to do this in a JSP instead of a Servlet. This is indeed not going to work. You need to send either the image or the HTML page exclusively in response to fully separate requests.
In your JSP/HTML page just have a link to the image, like so:
click to download image
Then, in a servlet listening on an url-pattern of /imageservlet/*, you just get the image as InputStream from some datasource (e.g. from local disk file system as FileInputStream) and then write it to the OutputStream of the response the usual Java IO way.
You only need to set at least the Content-Disposition response header to attachment to make sure that the client get a Save As popup dialogue, else it will be displayed straight in the browser. Setting the Content-Type and Content-Length are also important so that the browser knows what the server is sending and can predict how long the download may take.
response.setHeader("Content-Type", getServletContext().getMimeType(file.getName()));
response.setHeader("Content-Length", String.valueOf(file.length()));
response.setHeader("Content-Disposition", "attachment;filename=\"" + file.getName() + "\"");
You can find complete basic servlet example in this article.
Note: you cannot control where the client would save the image, this would be a security hole. This way websites would be able to write malicious files on client's disk unaskingly.
Update: as per your update, there are two options:
You need to let the client itself fire two HTTP requests (I've answered this in your subsequent question)
Create a client side application which does all the task directly at the client side and then embed this in your webpage, for example a Java Applet. With an applet you have full control over the client environment. You can execute almost all Java code you'd like to execute and you can write files to disk directly without asking client for the location to save. You only need to sign the applet by a 3rd party company or the client needs to confirm a security warning before running.
Its up to the browser how all types of output are handled. Web pages are given a content type of html which the browser understands and ends up rendering ass a page that we can see. Images are given content type of image/jpeg etc which are rendered as images when in a page etc. To force a download prompt one needs to use a content type of a binary file rather than that of an image so the browser forces the download rather than shows the image. To ensure this use something like "application/octetstream"... i cant recall exactly but its easy to google for.
Can you use AJAX to download a generated csv file from a web application? If so does anyone have any kind of reference that I could be pointed towards?
EDIT: Sorry I should have mentioned I am using Prototype's Ajax.Request and I looked in firebug's response tool and the generated CSV is the response, I just need to get it to pop up with the save file option after has been generated by the Ajax.Request
This is a known limitation of Ajax requests, you will need to use JS like:
window.location='download-csv.rb';
Instead of using an Ajax request. Another way is to change the location of a hidden Iframe, but this has it's own pro's/con's.
You will never get an Ajax request to display the 'file save' dialog, no matter what HTTP headers you send.
In light of your latest edit, to make your CSV file trigger a file download (instead of rendering in the browser), there's no need for Ajax.
Instead, the solution is to have your back-end system add this HTTP header when the CSV file is requested:
Content-disposition: attachment; filename=<your_filename.csv>;
Your implementation here depends on the back-end system you're using. If you're using Rails (as your username suggests), here's a start:
filename = 'your_filename.csv'
headers['Content-Type'] = 'text/plain'
headers['Content-Disposition'] = "attachment; filename=\"#{filename}\""
render :layout => false
Downloading it isn't the problem; you can download any data you like via XmlHttpRequest. The hard part is parsing it. There are several ways to parse it, from regexs to string indexing.
You can use "AJAX" to download anything .. Some people would say you shouldn't call it AJAX in that case since that term is rigorously devoted to downloading XML. But really it's just a mechanism to get data into the client w/o reloading a page. If you were loading HTML it'd be called AHAH, for CSV i guess you'd call it AHAC or AJAC? ..