I have been using Asp.Net Core MVC to load views and their content for several years. However, the trend seems to be pushing us strongly towards Single Page Applications (SPA). From my understanding, all html files are downloaded directly to the client. From now on we don't need to make requests to a server anymore in order to receive HTML, CSS, etc. because the routing of Vue (if configured properly) will serve the appropriate components.
All of this makes a lot of sense to me and seems like a good option. The thing I don't understand or am worried about is the loading time. Wouldn't it be extremly slow to download all files the first time when the website is called?
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I am learning MEAN Stack. I started from learning Angular(from angular.io) now I am learning node.js and express.js
My question is, if there is angular for front end in MEAN Stack then why there are views and template engines in express.js at back-end? Are they alternative for each other or complements each other? what is the boundary for the role and responsibility of these two?
I am looking forward for someone's help in clarifying of my concept for role these two technologies(express' views and angular) used in mean stack.
In order to answer your question, let me explain what is angular and what are template engines in express?
What is Angular?
Angular is a platform that makes it easy to build applications with the web. Angular combines declarative templates, dependency injection, end to end tooling, and integrated best practices to solve development challenges. Angular empowers developers to build applications that live on the web, mobile, or the desktop.
what is template engine?
A template engine enables you to use static template files in your application. At runtime, the template engine replaces variables in a template file with actual values and transforms the template into an HTML file sent to the client. This approach makes it easier to design an HTML page.
Some popular template engines that work with Express are Pug, Mustache, and EJS. The Express application generator uses Jade as its default, but it also supports several others.
So,
Angular is a framework with a templating component baked in. You use it to create Single page Web Applications which means that DOM modification is happening on the client side and the app exchange with server only data. If your concern is template it is plain HTML.
Whereas, template engines' rendered views are sent to client each time by server whenever request is made each time a new page is rendered on server and sent to the client which is Great for static sites but not for rich site interactions.
If there is angular for front-end in MEAN Stack then why there are views and template engines in express.js at back-end?
This is because not every time generating views from angular is recommended sometimes it is better to use Template Engines to generate views and send the rendered page to a client, generating views at client side has its own pros and cons and generating views at server side has its own.
Generating views using template engines (i.e. at server-side):
pros:
Search engines can crawl the site for better SEO.
The initial page load is faster.
Great for static sites.
cons:
Frequent server requests.
An overall slow page rendering.
Full page reloads.
Non-rich site interactions.
Generating views using angular engines (i.e. at client-side):
pros:
Rich site interactions
Fast website rendering after the initial load.
Great for web applications.
Robust selection of JavaScript libraries.
cons:
Low SEO if not implemented correctly.
The initial load might require more time.
In most cases, requires an external library.
So, after knowing the pros and cons, you yourself can better decide that in particular case which one is better for you. Mean Stack has provided options for developers.
As far as your question regarding the role of these two technologies is concerned, Angular is a lot more view generator only, It has features like routing, it as services two-way data binding etc while the template engines are meant to render HTML so that it can be sent to the client.
I hope you will find this answer useful.
References:
what is the template engine?
what is angular?
pros/cons
Angular is a full-fledged front-end framework that comes with its own way of doing templating, using angular-specific markup in your HTML. If you use Angular as your framework, you're more or less stuck with their way of templating within the Angular portion of your application.
Angular Features
It is a framework written in Javascript language
Manages state of models
Integrates with other UI tools
Manipulates DOM
Allows writing custom HTML codes
It is meant for javascript developers to create dynamic web pages in a quick time
NodeJS
It serves the web
It is runtime built on javascript engine in google chrome
It can be considered as a lightweight server which can serve client requests in a more
simpler way than java does
It performs communication operation with databases, web-sockets,
middleware etc.
Why we use angular for Tempting not Express/Node tempting Engine
Server-side rendering is the most common method for displaying information onto the screen. It works by converting HTML files in the server into usable information for the browser.
Whenever you visit a website, your browser makes a request to the server that contains the contents of the website. The request usually only takes a few milliseconds, but that ultimately depends on a multitude of factors:
Your internet speed
how many users are trying to access the site and
how optimized the website is, to name a few
Once the request is done processing, your browser gets back the fully rendered HTML and displays it on the screen. If you then decide to visit a different page on the website, your browser will once again make another request for the new information. This will occur each and every time you visit a page that your browser does not have a cached version of.
It doesn’t matter if the new page only has a few items that are different than the current page, the browser will ask for the entire new page and will re-render everything from the ground up.
How client-side rendering works
When developers talk about client-side rendering, they’re talking about rendering content in the browser using JavaScript. So instead of getting all of the content from the HTML document itself, you are getting a bare-bones HTML document with a JavaScript file that will render the rest of the site using the browser.
This is a relatively new approach to rendering websites, and it didn't really become popular until JavaScript libraries started incorporating it into their style of development.
See Examples HerePratical Example
Basically template engines in Express are mostly used for displaying 404 and other server error messages. I find them ideal for such use cases. Using template engines for complex front end rendering is bad and not a good practice.
Express JS is a web framework on top of nodejs http module. Whereas Angular JS is a front end framework which doesnot depend on NodeJs server to run. Conceptually both are similar in few features like routing whereas implementation is different
I have recently worked in a pure Scala-Play application and later in a pure AngularJS application. I'm very impressed with both and I'm wondering what is the sweet spot of combining the two frameworks together. Since the two frameworks can be complementary but also overlapping in different areas e.g. MVC and page routing, as far as I know these are some of the possibilities:
Single Page design, use AngularJS MVC-only and use Scala-Play as "dull" service layer backend with no full page refreshes.
Allow page reloads and each page reload becomes a different AngularJS root application. This seems quite flexible e.g. the client side is not bloatted with so much data for larger applications but better partitioned for the different use-cases. The downside is that I'd need different AngularJS MVC applications and I'm not even sure how to organize it as a project. Are there examples of this?
Typical server side Web App, use Play MVC-only and AngularJS for handling UI models for each separate page.
My choice of IDE for these types of architecture would of course be WebStorm but unfortunately I can't have all client-side (AngularJS and JavaScripts) and sever-side (Scala-Play) codes in a single project.
I believe that there is no the ultimate optimal architecture for combining Play and Angular. It depends on the specificity of the project, team etc.
The decision to develop UI part with Angular and the server side back-end with Play is very reasonable. Technically it may be done as following:
Development:
Both parts are developed as detached projects with the preferable IDE.
The client should have some entry point HTML page. It is reasonable to name it index.html, but is may be any other name.
For client-server integration do on the Play side as following:
Select a sub-folder under the play application root, which will serve as the "home" for the client files. The default solution is to use the folder public, since all files under it are automatically deployed.
All client files should be copied under the public folder. The files may be organized in any structure.
Add a route for the default URL as a route to the index.html. The argument path in the route should be the full path of the index.html relatively to the application root.
If index.html is directly in the public folder, the route is like this:
GET /defaultUrl controllers.Assets.at(path="/public", file ="index.html")
Add routing to the client files:
GET /*file controllers.Assets.at(path="/public", file)
Now the distribution package will include all the client files.
Putting of the client files into the public folder should be done automatically, for example by organizing the client directory structure and appropriate configuration of the client IDE.
You can find more examples in this post.
I am new to AngularJS.I have two questions.
Is it possible to use JSP pages instead of HTML in AngularJS.
Is it possible to create a web application using AngularJS without webservices (for fetching data from DB) and use HTTP servlet for that purpose
Is it possible to use JSP pages instead of HTML in AngularJS.
Even if you use JSP the final output will be HTML so you can use JSP in AngularJS but JSP files are mainly used to render the frontend with data that you can do using HTML only in AngularJS.
Is it possible to create a web application using AngularJS without web services (for fetching data from DB) and use HTTP servlet for that purpose
Whether you use plain Servlet or any framework that creates REST APIs, it will be HTTP calls only.
(This is a newbie question which applies equally to all front-end MVVM frameworks. I'll answer it for the general good.)
AngularJS is a front-end framework which runs in the browser. It relies on a server delivering the content (HTML templates, CSS and JS sources) to the browser.
What you use as a server, is entirely up to you. It depends on whether you need server-side dynamic content.
If none is required in that area, you can use a static HTTP server like LightHTTP, or plain old apache, or nginx, or anything else to deliver the AngularJS site to the browser.
But in most you will have some server interaction (i.e. storing / querying stuff in a database, or communication / synchronization with other users, etc). The common approach for that is to deliver HTML/CSS/JS statically and add a bunch of REST interfaces. Flask and Tornado are popular server choices for that, or stuff like spray.IO / akka.http for higher traffic volumes.
In specific cases, you may want to work with pre-rendered HTML templates (usually because you want to dynamically exclude parts of pages for security/user role reasons). Then you need a server-side framework with template rendering. Django, JSP, ASP, pick your favourite.
It seems like you are asking how to use AngularJs in a JavaEE application. And yes it is possible. Only your index.jsp will be in jsp, and all you other views will be in html.
You can then use http requests to fetch data through your servlets.
it can be useful. here are scenarios:
you want to save ram, cpu for mobile phones or machines that doesn't have lots of power. you can partially render page in jsp and keep only minimal in angular.
your team is traditionally jsp heavy and you want to use them and gradually transfer to angular. eg... for i18n rendering jsp seems far better. note that i18n may not add lots of values in angular and you may not want to throw up existing code in jsp.
I have been noticing strong views in stackoverflow and they seem to dismiss everything that doesn't fit in their utopian all new cutting edge. all the angular projects I worked had heavy dose of legacy pages using jsp and it doesn't make sense to rewrite everything from scratch or lay off whole team and start hiring from scratch. and thus, yes, jsp makes sense with angular.
We're developing a website with AngularJS, and would like to have static HTML files for every AngularJS page for search engines.
The site is small and static, about 10-20 pages.
Is there any task in grunt that can generate HTML files based on Angular app? E.g. it generates /static/about.html for /#about page of Angular app.
I saw services and scripts like PhantomJS, but they look too complicated for our case. As the site is static, we can run the task every time we're going to publish any changes.
PhantomJS is indeed the way to go. However, there is existing tools that do mostly what you want.
This one is a good example:
https://github.com/cburgdorf/grunt-html-snapshot
This will run PhantomJS through pages of your website and generate an HTML version of it. It can be automated via Grunt.
The only caveat is that you have to enter manually, in the configuration, all the pages you need to index.
Is it ok for what you need?
EDIT: This is also a quite interesting and complete article about SEO friendly Angular applications: http://www.ng-newsletter.com/posts/serious-angular-seo.html
They provide a few alternatives depending on your needs
How are single-page apps (SPAs) supposed to be faster when generally SPAs have to make multiple requests to get data for different parts on the page? As opposed to rendering server side, where the browser only has to make a single request to get the whole page?
I also remember reading somewhere that opening/closing a web request is the bottleneck sometimes in web requests.
So why does an approach that makes more requests per page is supposed to make web sites faster?
Because you only load what you need.
For example, on a "normal" web page, the menu, sidebar, etc. would have to be rerendered on each page, but with an SPA only the content gets changed.
In addition, think of this case: A website that displays 100,000 items on the front page (with pictures). In the traditional case, it will take a long time to load the page, but with an SPA you only load the "first screen" (i.e. what the user can see), and load the rest as he scrolls down.
In other words, SPAs aren't magic: it's just that they only need to update the bits of the page that change, which makes the response time lower for users (i.e. they can "use" the new contact faster).
If well done, they are faster because:
Part of the server workload is offset to the client.
Only the needed page fragments are loaded at any given time.
Redundant templating code is reduced. One template can style many items, as opposed to having to output a lot of HTML for a full page at once.
They also facilitate lazy loading and the download of new data during idle times, and parallelism: the concurrent downloads of elements.
Usually SPA are built with a lazy mode approach: get the info only when you need it and if you need it.
Also usually the data coming to and from the spa is in a format (json for example) which focuses on the data only. The presentation layer is a concern of the SPA and all the required assets should be already loaded.
So usually they are faster and more maintainable.
It is not always the case though.