I have an ASP.net webpage, that periodically (once in a minute) makes a call to my WCF REST service. My REST service responses some XML data. After getting it I make some further operations on that on server side in my ASP page.Note, this post data process in ASP is required, I can't avoid it. I know my life would be easier without this step, but I must do it.
After I'd like to pass this data in XML format to a client side javascript, that can parse it and show infos to the user based on this data. How can make this call from server side? What is the best pattern/practice to do it?
.net4/VS2010
if you want to call a function that already exists, that will load your data to the screen, you can tell the server to return your data and then ajax will grab that data and call a callback function.
if you are not using ajax, you can reload the whole page with the new data.
HTTP is not designed to push data from the server to the client. I'm not really familiar with ASP but usually you have the following possibilities to "push" data to a client javascript application via HTTP:
page reload via meta refresh (which doesn't actually push data;) )
periodically polling an "job queue" URL using javascript
comet (see http://en.wikipedia.org/wiki/Comet_(programming)) for an overview)
Web Sockets (which actually pushes data to the client but is only supported by newer browsers)
I've been using atmosphere (http://atmosphere.java.net/) which works pretty well in java application containers, which provides an abstraction layer over the underlying technology. I don't know if there is something similar out there in the ASP-world.
cheers
Martin
Tom, in that case just do the following
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I am a newbie in web development. I am in the process of building a food blog website. I want to pursue front-end-web-developer career. I have built my website only using client side languages like javascript, jquery, html and css. I have used json to store the data. my questions are -
1. I now want to make my website live. For that I want my website to be hosted on server. As I am not using any server side scripting, would my data related to website be visible to everyone if they do try to "inspect element" or "view source"?
2. how can I separate Json from client side code/scripting? I think for that I will have to seperate json data from other javascript code and store it into a separate file on a server. But in that case how can I access the Json data? For that I will have to make use of some server side scripting language. I prefer Asp.net(not that I know asp.net but I am familiar with C# hence). I also would have to make changes to my html code at client side to fetch the Json data from server. I am not really aware of this whole thing. Could someone spare some time and let me know how to go about it?
3. Does all the client side and server side code lies in a single asp.net project?
I have searched over internet. Mostly all the material/coding available over internet is mostly in php or python hence I am confused. There no definite guideline that I could find as how to handle the data part only using JSON?
to help you answer your 2nd question
2. how can I separate Json from client side code/scripting?
usually server side is in the controller so your HomeController.cs for instance will have an Index action (public ActionResult Index()) that method will basically be called whenever the browser hits the route Home/Index.cshtml
in order to separate these two, you may fetch or construct your Json in the controller and pass it to the ViewBag, from there you can access it in the view.
using $.ajax will help as well to get the json from the view and update the content of a specific part of your page for instance.
I'm about to start creating a website that takes values of form inputs(dropdowns, radial boxes, etc.) from the client(no user accounts involved) and performs calculations besed off of these values. These calculations are rather sensitive and I know client side javascript can't be made secure.
Is it possible to pull these client side values and run the calculations server side with node.js? If so, how secure is that? What other precautions can be taken?
If that's not possible or secure, what are some alternative solutions?
You have a couple options for sending the data to your server and then performing the calculations there.
You can put the data into a form and you can submit the form to your server. The server will then receive all the data from the form and it can do whatever it wants with the data. The server can then return a new page with whatever results you want to show and the browser will show the results page.
You can collect the data from your web page and send it to your server with an Ajax call made via Javascript. The server will receive the data from the Ajax call and can do whatever calculations it wants with the data. It can then return whatever data is appropriate from the Ajax call and the client will receive that data in Javascript and can then display it in the new page (or do whatever else is appropriate).
Code to make calculations on your server will be as safe as the security is on your own server (which can be made plenty secure). Server-based code is not normally available to the outside world.
If you are concerned about security of the data or result in transit, then you can use https between your webpage and your server.
When you ask about "security", folks can provide better answers/info if you say more about what you're trying to protect, why you're trying to protect it and what types of threats you're trying to protect it from. Security is best designed and implemented for very specific reasons and you haven't provided any of those type of specifics.
I'm in search of some best practices. I have a webpage asp.net (a loading page as you will).
Once this page is loaded (and visible to the user) i want to execute a function that might last some seconds.
problem is, how do i launch this function?
I've tried loadComplete (event),unload (event) , working with timeout (javascript to poll itself with json) and even the timer-class (.Net). Could anyone point out an alternative/ best pratices to perform this kind of action?
This won't work the way that you are trying to do it. To understand why you have to understand the concept of webservers:
Webservers use some code (PHP, ASP.NET, ...) to generate dynamical HTML code that is beeing sent to the client. This process works in the following steps (in case of ASP.NET)
Client requests something from the server.
Server generates html (that's your ASP.NET / C# code)
Server sends HTML to client
The browser on the client receives the HTML and displays it.
So your ASP.NET code is only running in step 2. This makes it impossible to catch the event when the client has rendered his page in his browser. However there is client-side technology called AJAX. You can make AJAX calls using javascript (that runs in the browser of the client).
So for example you can create a javascript function that sends a second request to the server when the html was loaded in the client, and executes some function on the server.
For this you will need a webservice on the server that will serve as a interface between the javascript and your C# code.
A easy way to create webservices is to use WCF webservices
If you have any further questions feel free to comment on this answer.
I want to create a web application that displays data from a public api. I will use d3 (a javascript data-visualization library). I want to retrieve data from the api every ten minutes, and update my page (say it is traffic, or something). I have not built many web applications, how do I get the updates?
Should the js on the client side use a timer to request updates from the server side of my application (perhaps the application is written in Rails or node.js). The server then makes the api call and sends a response asynchronously? Is this called a socket? I have read that HTML5 provides sockets.
Or, perhaps an AJAX request?
Or, does the server side of my application create a timer, make the api call, and then "push" updates to the view. This seems wrong to me, there could be other views in this application, and the server shouldn't have to keep track of which view is active.
Is there a standard pattern for this type of web application? Any examples or tutorials greatly appreciated.
An AJAX request (XMLHttpRequest) is probably the way to go.
I have a very simple example of an XMLHttpRequest (with Java as the backend) here: https://stackoverflow.com/a/18028943/1468130
You could recreate a backend to receive HTTP GET requests in any other server-side language. Just echo back whatever data you retrieved, and xmlhttp.onload() will catch it.
Depending on how complex your data is, you may want to find a JSON library for your server-side language of choice, and serialize your data to JSON before echoing it back to your JS. Then you can use JavaScript's JSON.parse() method to convert your server data to an object that can easily be used by the client script.
If you are using jQuery, it handles AJAX very smoothly, and using $.ajax() would probably be easier than plain-old XMLHttpRequest.
http://api.jquery.com/jQuery.ajax/
(There are examples throughout this page, mostly-concentrated at the bottom.)
It really annoys me how complicated so many of the AJAX tutorials are. At least with jQuery, it's pretty easy.
Basically, you just need to ask a script for something (initiate the request, send url parameters), and wait for the script to give you something back (trigger your onload() or jqxhr.done() functions, supplying those functions with a data parameter).
For your other questions:
Use JavaScript's setTimeout() or setInterval() to initiate an AJAX request every 600000 milliseconds. In the request's onload callback, handle your data and update the page appropriately.
The response will be asynchronous.
This isn't a socket.
"Pushing" probably isn't the way to go in this case.
If I understand correctly and this API is external, then your problem can be divided into two separate sub-problems:
1) Updating data at the server. Server should download data once per N minutes. So, it should not be connected to customers' AJAX calls. If two customers will come to the website at the same time, your server will make two API call, what is not correct.
Actually, you should create a CRON job at the server that will call API and store its' result at the server. In this case your server will always make one call at a time and have quite a fresh information cached.
2) Updating data at clients. If data at customers' browsers should be updated without refreshing the page, then you should use some sort of Ajax. It can make a request to your server once per X minutes to get a fresh data or use so-called long-polling.
I think the most effective way to implement real time Web application is to use Web socket to push changes from the server rather than polling from the client side. This way users can see changes instantaneously once server notify that there is new data available. You can read more on the similar post.
I have tried using nodejs package called socket.io to make a real time virtual classroom. It works quite well for me.
I want to have a dynamic webpage that automaticly updates some information, this information should be received from my c/c++ application using HTTP. I have set up a socket and can send HTML and Javascript files to the browser.
I don't know how to move on. How to encapsulate my data into XMLHttpRequest objects? Or maybe this isn't the way to go? The problem is that my c/c++ application will be run on an embedded system that can't really support php or something like that.
I can't really understand how XMLHttpRequest works, I only find a lot of client examples on the web and not much about how a server should handle it.
A server should handle it as any other request. From the servers point of view, it's a normal HTTP request. Return the data that the client asks for! This is usually a HTML fragment, some XML or some JSON.
Ajax just send normal HTTP GET POST ... request, you should make sure your response header is correct, such as Content-Type.
How do you send information to the browser? The browser is client-side. To get information, you must either query the server (which you say is written in C++). If you want your client to receive request, you should probably emulate a server-like behavior using NodeJS.