I am new in rails. I don't understand how rails process the request and response.
When I enter the url into browser for rails app and press enter. Then can any one walk me through what heppens in detail.
When you types in a URL, hoping for a your page.
After the DNS gets resolved, the request hits a web server, which asks Rails what it has for that url.
Rails goes to the routes.rb file first, which takes the URL and calls a corresponding controller action.
The controller goes and gets whatever stuff it needs from the database using the relevant model.
With the data the controller got from the model, it uses the respective view to make some HTML.
Rails packs up the response and gives it to the web server.
The web server delivers the response to the browser to display your page in the browser.
A good read:
Examining Internals Of Rails Request Response Cycle
In very simple terms,
Action controller takes control of request/response routes with the help of routes.rb
http://guides.rubyonrails.org/action_controller_overview.html check this out for details about Action controller.
When you fire a rails request respective to your app,
Action controller processes the request and matches it with the routes in routes.rb. For example when you hit
localhost:3000/about_us
The routes are matched with "/about_us" => "home#about_us" it takes you to the home controller's about_us action, which in turn holds a view (view/home/about_us.html.erb) that would be displayed.
Related
I have a application in ZF2 framework, in this I am sending and requesting data to/from a web services using http_client request. In my application I have a multi step form which is changing form steps using ajax.
Now if I submit a form using ajax request, it hit my controller and then from controller I call a common function of controller plugin for all type of request in this case if there is any error in web service then I want to redirect to login page but it not redirecting parent layout/page instead of this it show the login page in ajax loaded form part(where my form is changing through ajax).
Please help me to redirect main page to login page instead of show login page in ajax loaded part.
Thanks in advance
I'm not a javascript expert but you need to do the redirect in the javascript and not your controller.
window.location.replace("http://stackoverflow.com");
You can pass the redirect url from your controller if you need to redirect to different locations depending on your logic.
See this question.
Hope this points you in the right direction.
I have an app where I try to adhere to REST.
The app receives requests for external links that don't belong to the app, so the sole purpose of the action is to redirect the request to the external URL.
My suggestion is to have the following controller/action: redirects_controller#create.
Is my thinking correct or should it be the show action instead?
REST (apart from Rails) is about using the correct HTTP method for the correct action. The Rails part is just using the conventional controller action for a given HTTP method.
So, if you're doing a 301 or 302 redirect to another page, which browsers handle by issuing a GET request to the URL in the redirect response's Location header, do it in a show action. This will allow the user's browser to cache the other page when appropriate, and to not notify the user before redirecting.
(There is a way to redirect POSTs, but you didn't mention it so I expect you're talking about regular 301/302 redirects.)
Coming from a Java background, the REST actions must be related to CRUD operations. Requests that do not change the resource like in your case where the intent is to redirect to another page must be tied to a GET verb or show in your example.
If you were to create a new resource you would use POST.
A more detailed explanation can be found in Richardson's rest maturity model level 2
Is it possible to run a request command on a set of multipartFile objects for a set of selected files that has been passed to an second action from an initial action that received them from an type file input html tag.
I can access the multipartfile object as a string in the redirected (second) action -
Such as:
form:org.springframework.web.multipart.commons.CommonsMultipartFile#35d79259
But I am unable to run a request command such as request.getFiles - also I cannot cast it as a MultipartFile.
The redirect to intentional - let me explain what I'm trying to do in more detail:
I have a file upload web page with an input form that sends the selected files (multpartFile objects) to the action. Prior to uploading the files from the client I want the user to have a web page where he adds extra data to each file prior to uploading (metadata tags). To do this I was going to redirect to another action that displays a web page with the list of the files (having transferred the params data that contain the files selected from the original web page to the redirected action) and input fields for the user to add tags. In short the redirect is intentional.
I guess the correct way to do this is using js on the original web page - just wanted to see if I could do it this way instead?
-mike
In general redirects use GET, so there's nowhere for the form body and uploaded file(s) to go. POST/UPDATE/DELETE actions make changes, and a redirect is typically an indication that something went wrong, e.g. something mild like a url changed (301/302), or something more serious like an authenticated user trying to access a page they have no permission for, or an unauthenticated user trying to access anything guarded (401/403).
You wouldn't want to pick up where you left off from a lot of scenarios that trigger a redirect (and it wouldn't be practical at all) so it's common to not attempt to do anything with form or file upload data and let the user re-do the action.
Well, so far in each article I see people say server respond accordingly to the request type. If it is xml request then response is in xml and if it is ajax or html then response is in ajax or html. Browser send the request and server respond accordingly. My question is in rails app in which part this decision is taken? That is by server which part of the rails app we indicate?
This decision is taken inside the controller of the rails MVC framework and can be modified by the user. The user may wish not to respond to a particular type of request.
The distinction is made by suffix in URI, eg. ..../users/123.json. And You do it by yourself in controller.
I'm a novice in ruby on rails trying to understand the in-depth flow of a typical request/response life cycle in ruby on rails web application.
I have googled for the info and have not found an answer which is complete or detailed to the level of DNS servers to dispatchers.
The closest I got to a good explanation is at:
http://brainspl.at/request_response.pdf.
Can someone point me to a better or more detailed explanation?
-Raviteja
So you are asking for rails request/response cycle and you already referred to a presentation which really describes it very well. So im assuming that you want to know it from a very high level and you need this concept totally for development. Then here it is. Im just trying to name the parts sequentially.
Route: Here you will draw the paths which will be used by the world to access your application. With a complete RESTful architecture, you need to define the hierarchy of your resources and define how a resource can be accessed to perform some action. If any request to your application doesnt match with any path in the routes file, it will not be processed. If any match occurs, it will find the corresponding controller and action and will call it. At the time of calling, it will store all the request related data in params hash.
Before Filters: Now your application already know which controller#method is gonna process the request. And it will check if there is anything configured to execute before calling that method. This is done by using before_filter. If found anything then those functions will be called first.
Method Execution: After executing all the before_filter methods in a particular sequence, it will call the actual method. All the data is available in params hash in this method. It processes input data, invokes Model calls for database access, and prepare data for view.
View: Proper view file will be chosen based on the controller#action, format. Or you might select any particular view to render by render :partial call. And the response will be prepared using the variables prepared in controller. This response will go to the client.
After Filters: After processing the view, it will look after_filter methods and will those if found.
Well this was a quick overview i would say, without really any details. Im saying again, the pdf you referred really contains more details.
Let me know if you want to know anything more specifically.
A user opens his browser, types in a URL, and presses Enter. When a user presses Enter, the browser makes a request for that URL.
The request hits the Rails router (config/routes.rb).
The router maps the URL to the correct controller and action to handle the request.
The action receives the request, and asks the model to fetch data from the database.
The model returns a list of data to the controller action.
The controller action passes the data on to the view.
The view renders the page as HTML.
The controller sends the HTML back to the browser. The page loads and the user sees it.
https://www.codecademy.com/articles/request-response-cycle-dynamic
and https://www.codecademy.com/articles/request-response-cycle-forms
Everything starts when ‘url’ requested by a user. The browser needs to know sever’s IP address to connect, So it lookup DNS(Domain name system) which translate your domain into the public IP address of the particular server. Then the Browser will do threeway handshake to connect server like puma in port 80. And decide upon public and private key it happen only because if url use HTTPS. HTTPS is a secure wrapper around HTTP and TCP. Then Server triggers the rails application through middleware like rack and provides request verb, header, body to the application. Then rails application use Journey (Default route library of rails) to find the consent controller and action which matches the request and call with the request and params.
Then rails lifecycle callbacks like before, after, around will be triggered during the process. The action takes care of requesting data from the model and rendering the consent view for the request. Finally sent back the status, header, and body as the response.
If you want to learn in-depth about lifecycle, check this article The Lifecycle of a Request
It is also important to note that Rails apps use an MVC architectural pattern, which is Model, View, and Controller at a high-level the life-cycle of a request in rails app is simply the interaction of the Model, View, and Controller. This article gives you an overview.