is there any small example application in On next with GraphQL backend (few pages, queries and mutations)?
I'm doing presentation about Sangria (Scala GraphQL server library) and I want some frontend for it. And also I'm curious about Om for longer time.
Related
I have a microcontroller that monitors 4 different sensor variables (temperature, pressure, weight, speed) with each variable being read at a different rate. The microcontroller also runs a lightweight webserver. I want to create a simple webpage such that when a client connection is made to the webserver, it will display the values of the 4 variables. While I am somewhat familiar with HTML I can’t figure out how to populate a webpage with the data.
Am looking for some pointers on how to do this.
Secondly, I know the page that is displayed is static. How can it be made dynamic in that when a new value is read, the page is updated with that value.
I am sure there are ‘standard’ ways to do this but I have no clue what the mechanisms are called or how they work.
Any guidance is really appreciated. – Thanks!
J
Perhaps SSI (Server Side Includes) is what you need to show dynamic data inside HTML page. Usually lightweight webserver for micro-controller would had this feature implemented already.
You need to implement Web 2.0 feature by yourself to extend your lightweight webserver. For client side you can use the js library from Socket.IO
Alternatively you can have a socket.io server (by python) play for this web 2.0 feature, and your micro-control just update its data to the web server by JSON API. Then socket.io server update the received data to the clients. This is what I've done on my previous MCU project.
I'm designing the architecture for a new web application.
I think that communications between the backend (server) and the frontend should be JSON only.
Here are my arguments:
Its the client responsibility to manipulate and present data in its own way. The server should just send to the client the raw information needed.
JSON is lightweight and my application might be used by remote clients over poor mobile connections
It allows multiple front-end developments (Desktop devices, mobile
devices) and has the potential to create an API for other developers
I can't see any counter-argument to this approach, considering that we have internally the frontend skills to do almost everything we need from raw JSON information.
Could you provide counter-arguments to this JSON-only choice so that I can make a more informed choice?
There must be some as a lot of backend frameworks (think about the php ones) still advertise HTML templating to send HTML formatted responses to the clients.
Thanks
UPDATE: Even though I researched the topic before, I found a similar and very interesting post: Separate REST JSON API server and client?
There are many front end based framework already in market which support a Json very efficiently,some of them are backbone,underscore,angular etc.Now if we talk about backend,we generally use REST based communication for such type of application.So i think this type of architecture already exits in market and working very well,specially if i talked about mobile based application.
Although this question is dead, I think I should try to weigh in.
For all the reasons you stated and more, communication between the back-end and front-end via only JSON files is maybe the best way available, as it provides a more compartmentalized structure for your web application, and at the same time drastically reduces the data sent over your users' connection.
However, some drawbacks that are a direct consequence of this are:
Need for a lot more JavaScript front-end development (as the HTML structure is not being sent by the server and needs to be created in the client)
It shifts the pressure from the server to the client, thus there is more JavaScript for the client to run (this can sometimes be a problem especially for mobile users)
I want to make a django server to refresh the content that you approach the database, if the idea is to first make the user see the current contents of the database and as the valley became the new content, this content comes and is placed above the previous content without reloading the page, in another part of the site is to make you change the current content with the new as it gets to the database?
evserver clearer is my choice, but really do not know how and what would be the most simple and efficient?
I think you should avoid HTTP Polling. Here's why:
if the frequency of the setInterval combined with the number of users on your web app is going to lead to a big resource drain. If you go through slides 9 to 19 in this presentation you'll see some quite dramatic figures for using Push (Note: this example uses a hosted service but hosting your own realtime server and using Push also has similar benefits)
between setInterval calls the data displayed in your app is potentially out of data. Using a Push technology means the instant that new data is available it can be push and displayed in your app. You don't want users looking at an app and thinking they are seeing correct information when they are not.
You should take a the following StackOverflow questions:
Django / Comet (Push): Least of all evils?
Need help understanding Comet in Python (with Django)
For Python/Comet see:
Python Comet Server
The latest recommendation for Comet in Python?
I'd recommend you also start considering "WebSockets" as well as "Comet". Most Comet servers now prefer to use a WebSocket connection when possible.
If you'd prefer to avoid installing and managing your own Comet/WebSocket solution then you could use a realtime hosted service which will allow you Push data through them using a REST API and your clients can receive events by embedding a JavaScript library and writing a small about of code to subscribe and receive the event.
The steps are quite straightforward:
Write a model to store data in DB
Write a view that will generate JSON-serialized data upon POST request.
Write a template that will contain JavaScript with setInterval() that will
proceed AJAX requests to the view and render recieved data. (I'd suggest using JQuery as it's well documented and widespread).
I'm not a Web Developer, and I don't know a lot about the web application frameworks out there.
Recently, however, I got into Wt. It's a web framework written in C++ (that's why I got into it), but what impressed me the most is the idea it's based on.
Its API is different from any web framework I ever heard of (CppCMS, Yii, Django, Pylons, Zope, Drupals, Java Servlets, Struts ...): a new Application object gets created for any user session, and it stays alive until the session expires (only at this point the Application object gets destroied). This Application object works like a desktop window: you put Widgets in it (widgets like forms, links, labels ...); when the user clicks on a link (when the HTTP server receives a new GET/POST request) a function gets called on the object tight to the user session (in a nice Signal/Slot way), which can remove/add/change the widgets, thus changing the page the user will see.
As I said, I'm not very skilled with web frameworks, I develop almost only desktop applications; maybe for this reason I think this paradigm behind Wt is great.
I'd like to know what are the pros and cons of this framework API in respect to the other ones, and if there are other frameworks (also in other languages) based on the same concepts.
Wt is a great framework for its intended range of applications.
Wt is great for :
web apps tightly coupled to a session, i.e.
made to be accessed only by users that are logged in (except the landing page)
display a lot of user-dependent content (so not for a wiki)
relying heavily on state
web apps that need to have a lot of controls/buttons and user input.
For exemple, I plan to write a browser MMORPG. Pages will all be having a state tied to a user, and there will be a lot of buttons. Wt is perfect for that. I used to be a Ruby on Rails developper, and switching to Wt for this kind of app was a great moment. It's increadibly cumbersome to design forms with traditional frameworks that try to enforce pure REST.
Wt would also be perfect for a control interface on some process. For example, an interface allowing your customers to configure their adword campain, etc.
Of course, using Wt is not perfect regarding control and separation, but it allows extremely fast development when you need only the "classic" features (buttons, editors, etc.)
So as a rule of thumb, if you are trying to put a desktop application on the web (which is a great idea, removing the need to deploy and update on your customers' machines), Wt is a good candidate.
Also, if you are interfacing with an existing C++ codebase, Wt has an advantage.
I think this is generally bad idea.
Web application is very different from GUI one and there are many reasons:
99% of the web is about the content rather then about iteration.
You go to web to get or share content rather then to do some real time interaction
like drawing a picture, working with spreadsheet or anything else.
Web is content driven rather then "event driven" interactive application.
This has strong impact on how do you create most of web - you bring information
to user rather then interact with him.
The server and client programming is very different
There are some web GUI applications like e-Mail, Chats clients but to perform well
they require very good separation between the client side written
in high quality Java Script and the high quality server side backend that is used
over AJAX for content retrieval.
Hiding this separation like Wt does or (other known frameworks) lead to crappy
software and generally brings more problems then solutions in long run.
Because it should be very clear separation between server side and client side jobs
as some require real time response and some don't.
When you try to solve all this in one wait for problems. Note, there are client-server
solutions for GUI (see X-Server as example) but unlike web they designed for this
and rather work more like IPC rather then client-server solitions.
The web is stateless most of the time.
Or to be more correct the state usually keeps quite small amount of data.
Creation of instant session object is nice idea until you need to...
Scale up save state in long terms then this model becomes not so good, of course
this not "forced" model by Wt but it is general concept that fits certain concept
and some does not.
Bottom Line
If you want to design good GUI like web application. Start learning JavaScript and use good GUI JavaScript frameworks that fit well to GUI even driven design. Then combine them with some server side API using some interaction RPC model like Json-RPC, XML-RPC and other
AJAX tools.
This is the way to do things right for highly interactive applications.
If your application is more content oriented then most of server side web
frameworks do great job - concentrate on server side with its great tools suitable
for the job.
All in one solution? It just does not work...
Disclosure: I'm developer of CppCMS and I think Wt just goes in wrong way.
ASP.NET is similar; it has the same goal to make web development look like desktop application development.
I want to design a website but I don't know from where to start.
Is there a beginners' guide to start with?
How much dedication do you hope to provide? If you merely want to design a single website, quickly and dirty, there's a plethora of open source web templates available online, with clean and basic HTML/XHTML design strategies that you could modify, and provide content for.
Such as this and that.
Alternatively, if you would like to design your own websites from scratch and have full technical knowledge in the field (the proper way). Pick up a book or two on HTML/XHTML/XML, with documentation on content management systems, php, etc.
You'd soon find that in the beginning your development would be gradual and at best, slow. If you put in sufficient effort, you would find that you get to the point where you can quickly design sites confidently, which best illuminate your content.
You should be familiar with this and this
Try this Web Design from Scratch
I understand by website you mean some kind of web-app. And by design you mean, not just the page design but the design of the web-app. First, you have to understand the anatomy of a web-app. The major components are:
Database is used to store user and application data for long term. A database provides query functionality (SQL), backup on one installation and restore on another, triggers when a data entry changes, and constraints that must be satisfied by the data tables.
Web Server, also called Http Server hosts the web application.
Web Browser such as Internet Explorer or Firefox.
When a user types a URL into the web browser, the web server forwards the URL to the corresponding web application. The web application performs the needed tasks (which may involve reading or writing into the database) and returns a new html page to the user via www.
Some components of the web application are:
Database access objects are representations of objects that encapsulate interaction with database tables.
Business Logic is the main logic of the application. Here we implement the search functionality using Lucene library, for example.
Action Handler handles a http request received from the user, for example when she types a URL or when she clicks on the "submit" button. These are Http GET and POST requests. The Action Handler uses the business logic to drive the actions.
Data view on the web brower is constructed using some template library (which usually produces javascript user interface code for the web browser). For interactivity one may use Ajax techniques.
Almost all web-apps separate the model, view and controller of a web application. The view deals with the display, the model deals with data and the controller deals with control/functioning. See http://www.uidesign.net/Articles/Papers/UsingMVCPatterninWebInter.html.
Several frameworks implement MVC. The most easy ones to get started are Ruby on Rails and Django (over which an open source social network called Pinax too is written). There are much more comprehensive frameworks and libraries in java too (for a single web appl you may need to join several of these libraries), such as spring, webwork, tapestry, lucene (for search), sitemesh (for page decoration). Many java web apps run on tomcat web server and with mysql database.
I started with http://w3schools.com. Make sure you're using Firefox and the Firebug addon. Get your hands dirty then get familiar with the web design community.
I have CSS Mastery by Andy Budd on my desk and it's a good, readable, short, yet deep guide to CSS.
Don't Make me think has also become my mantra of web design.
Overall, you're going to produce a lot of crap--as I have--before you get good. If you have someone to look over what you're doing that'll be the best help. Personal drive will matter the most in the long run though, so stick with it and keep learning.
Liz Castro has a good book too.