Architecture of web applications

I consider software development more art than exact science, and as such, in software development almost always there is not a single way of solving a problem. Although there are defined best practices, it is a matter of problem being solved and the knowledge of the team that influences most the definition of the architecture of web applications and software applications in general.

Recent years has brought to popularity using REST in the architecture of web application solutions. I am a huge fan of REST, I like it a lot mostly because of its consistent way of expressing CRUD operations and brings simplicity to the API implementation. The use of REST has been pushed further with advancement of MV* JavaScript frameworks as they tend to have a natural way of consuming resources from REST APIs.

Lately, I am seeing that most newly built web applications tend to use REST in some way, if not exposing APIs, they do consume one or more of them. In my opinion, REST tends to create a viral effect on developers, as much as you use it, you want more of it. Now after we experience REST, I think there is a question which pops up:

Do we have to expose everything as REST API?

The universal answer “it depends” applies here very well! If you want to use a client side framework such as AngularJS that does not need server-side code and is well suitable to consume REST services, it might be a very good idea to expose the whole business logic as REST API and consume it through AngularJS services. This comes with additional benefit that if you want to have a mobile app of your web application, you do not have to write any additional code on server-side to support your mobile app, just consume the very same REST services and you are good to go. A diagram representation of such layered architecture of web applications could look like this:

Web application architecture with REST API and client side MV*

This is one of the most often used architecture styles I am seeing these days in web applications. However, what if you are not keen to using MV* JavaScript frameworks and want to use a server-side backend and generate your HTML representation using let’s say ASP.NET MVC. Do you still need to expose business logic as REST API?

Exposing business logic as REST API or any other form of service layer, if you do not have multiple types of consumers (web, devices, etc.), in my opinion is waste of resources (time and effort). Exposing and consuming services do introduce a level of complexity (you need to put extra effort on error handling, security, versioning, asynchronous access, etc.)  to the architecture and application code. This complexity is non considerable if you have multiple consumers of your application as it avoids writing multiple times the same functionality, however, if there is only one consumer and it is the web GUI, then in my experience I have seen that it only makes things worse. In such a situation, going with an old style server-side backend is a lot more easier. If you say I have a mobile client as well which consumes part of the functionality, in that case I think it is better to create a small REST API service group exposing only that part of the functionality, is a better choice. This will also allow you to develop your web app and mobile app in different paces (if you have lack of developer resources, you shall come to this requirement). The modified version of our new architecture will look like this:

Web application architecture with server-side backend and rest api

Sometimes we are keen to jump to new technologies and architecture styles just because its presentation looks attractive and we like to get our hands in it and give it a try. Often this pushes us to situations which makes maintenance of our code base difficult in later stages of our application lifespan. It is very important that evaluation of the application architecture to be done as early as possible and be judged from the simplicity and maintainability perspective.

 

Staying up to date with technology developments

For a software developer, staying up to date with technology developments and follow latest trends of software development is of utmost importance. But nowadays, the number of online posts/activities that are competing for our attention has increased exponentially. Dealing with all this load of information and staying up to date is not an easy thing. I have create a simple strategy which works for myself and I’d like to share it with you.

 

Conferences to follow/attend

Conferences are where the latest developments usually are formally announced and demonstrated. Attending developer conferences gives me the opportunity to listen to the demos and presentations of latest trends in software development as well as network with my peers. Sometimes, attending conferences is costly, especially if you target one of the major conferences, but luckily, most of those conferences publish their videos online so we can view them.

Some of the major conferences I follow are:

User groups

Local users groups provide excellent opportunities to see what your peers are up to, what is happening on the market, and what technologies and trends are actual in your neighborhood. There is also a value added activity of networking with your peers which is a good benefit. There is a user group for almost anything out there so just search for user groups at your neighborhood and join them.

Sites to follow

There are some major sites where I follow latest developments on software development technologies and practices, and entrepreneurship (in my opinion, developers should be quite familiar with what is happening on the business world as well) . Of course the list of the sites will be relative to your interests and platforms you use, but here is my list:

Persons to follow

Every industry has its own influencers who evangelize technologies and practices, and sometimes these people define the trends the industry follows. It is very important to chose who you follow as in some ways, by following a person you accept his influence to some degree and if this person is a successful one, you will benefit positively from his experience and thoughts.

Here is a part of the list of persons I follow:

Conculsions

It is quite challenging to stay up to date in this dynamic world, and we need a process in order to excel. Having a defined and structure workflow of flowing the information in and getting most of it will be a skill we all have to master. Depending on the technologies you use, the market you work in, or your interests, most probably your list will not be same as mine, but the principle behind is valid for any interest I think. It is important to define your standard sources of information and supplement them with additional sources from time to time or even substitute your standard sources with new ones after some time.

What are your sources of information?

 

* Head image source: http://mashable.com/2014/06/25/google-io-everything-to-know/ - Google IO Conference 2014 

Microsoft Certifications: Web development path

Microsoft Corporation offers a rich set of possibilities when it comes to education of new and existing software developers. Taking certification exams and certifying your knowledge is one of the best ways to build a solid knowledge base, improve your skills, and get ahead with your career in software development. In this post I will describe what it takes to follow Microsoft Certifications: Web development path.

In this wide range of certifications, where does one start from? Well, it depends on your current skills and work experience. If you are new to software development with less then one year of work experience or so, then my suggestion is you start with Microsoft Technology Associate (MTA) certifications.

You may start with  following MTA exams:

Software Development Fundamentals (Exam: 98-361)
Web Development Fundamentals (Exam: 98-363).
.NET Fundamentals (Exam: 98-372)
HTML5 App Development Fundamentals (Exam: 98-375)

For the complete list of MTA certifications please see MTA Certifications web page.

MTA certications are optional and are useful only if you do not have work experience developing these solutions.

What after that? The next part of the path is of professional certifications. The web development path leads to Microsoft Certified Solutions Developer: Web applications (MCSD). This title is awarded to anyone who passes these exams:

Programming in HTML5 with JavaScript and CSS3 (Exam: 70-480)
Developing ASP.NET MVC Web Applications (Exam: 70-486)
Developing Microsoft Azure and Web Services (Exam: 70-487)

When you complete all of these exams, you will get the title of MCSD: Web Applications which will certify your knowledge in the field of developing web applications using HTML5, CSS3, JavaScript, and ASP.NET MVC.

Offline availability with AppCache

Offline availability of your web application will give a little extra comfort to your users. If using Local storage an appropriate choice to enable web applications to work offline with dynamic data (see my post on Local storage), Application cache (hereafter AppCache) is a good choice for making the static content of the web application available offline.

About AppCache

AppCache enables developers to specify a set of files which need to be cached by the browser. While cached, the requested resources will be served from the disk and this will make your web application available even when users are offline.

Caching static content has several benefits which you may like to leverage, including:

  • Better site performance, as static content will be served from the disk and not requested from the server
  • Better server performance, as less resources will be served and bandwidth will be preserved
  • Users will have the possibility to access your contents while offline, leading to better user experience and satisfaction
  • Mobile users can use the web app even when they are out of internet coverage
  • Mobile user can bookmark/pin the web application to their phone and use it later as a mobile app (offline)

The cache size limit may vary between browsers, but a cache size of 5MB can be expected from modern browsers, and with users permission, the size can be increased if needed.

How do we tell the browser to cache our site, and most importantly, which files to cache. We can do this using a special file called Manifest file. We tie manifest file to the html root element using manifest attribute. e.g.

<html manifest="webapp.appcache">

It is recommended that the extension of the file is .appcache.

Manifest file structure

Manifest file is a simple text file which should be served with “text/cache-manifest” content type. The very first line of the file should be:

CACHE-MANIFEST

and after that files to be cached are listed one per line.

index.html
css/main.css
css/theme.css
js/lib.js

Folders and wildcard specifiers are also permitted.

The common practice is to follow this structure:

CACHE MANIFEST
#23.10.2014 v1.0.10
/file1.html
/file2.jpg

NETWORK:
posts.php

FALLBACK:
offline.html

On the first line we have put the mandatory declaration of “CACHE MANIFEST”. Then on the second line we put date and version as comment. After version, we start declaring files/folders which are to be cached. The “NETWORK” section shows which files should not be cached as they change frequently, and last, with “FALLBACK” we specify what should be used when a resource is unreachable.

The comment part with version number has a significant importance here. The browser will not ask for the cached files unless one of these two is true:

  • The cache is deleted
  • The manifest file has changed

We best note the change of the manifest file by putting a version number in it. Whenever we do a change in any of the cached files, we simply increment the version number to advise the browsers to re-cache the files.

Specifying the manifest file will make the browsers cache the content specified and make the static content of your web app available offline.

 

HTML5 Local Storage API

It has started to become a common requirement for Web applications to have some support for offline usage. HTML 5 local storage (hereafter local storage) is one of the options to consider when you need to support offline use of your web application. But what is local storage, and when should you consider it. Let’s go through what you need to know before you start using local storage.

What is HTML5 Local storage API?

Local storage is a storage of key-value pairs (KVP) which you can store and access using a JavaScript API. It is supported by most of major browsers (even IE8 does support it :)). The KVPs are string values of information used to store in the storage of the browser

e.g.  “CMS” => “WordPress”

Local storage has several advantages over Cookies and can be a good substitute for them. Cookies have the size limitation of 4KB, on the other side, the usual supported size for Local storage is 5MB. Also, cookies are sent to the server with every request, overloading the bandwidth, whilst, Local storage is not sent to the server any request, instead, only the required value is send.

Local storage is a persisted storage and have no expiration time. The data persisted will stay until cleared. There is another variant of browser storage which is temporary, and that is Session storage. Session storage is used only for the session, and when session expires or is destroyed, so is the session storage.

Storing and reading from Local storage

Before starting to use the Local storage, it is advisable you always test first if it is supported by the browser, and you do it with a simple check like this:

if (window['localStorage'] !== null) {
//your code here
}

Storing values to Local storage is done using setItem() function. This method accepts two parameters, the first one is the key, and second parameter is the value. e.g.

localStorage.setItem("cms", "WordPress");

If we open chrome developers tool in resources tab, we can see the values in local storage, and there is our “cms” key with value set to “WordPress”

Local storage in chrome developer tools

 

Reading the stored value is done using getItem() function and supplying the key as a parameter. e.g.

var cmsValue = localStorage.getItem("cms");

Other functions

There are several other useful functions which you can use with Local storage. If you want to get the total number of keys stored you can use localStorage.length property, or if you want to remove one item from the storage you can do this by calling removeItem function. e.g.

var numberOfItems = localStorage.length;

localStorage.removeItem("cms");

It is also possible that you clear the whole list of items stored by calling function clear e.g.

localStorage.clear();

Events

In some more advanced scenarios, you may want to track changes in local storage, that is where events come in. Events are out of scope of this post, however, it is good to remember that they are there should you have such a requirement.

References

If you want to get in details, the specification of the local storage can be found in this link: Web Storage specification

Certification 70-486: Developing ASP.NET MVC 4 Web Applications

Last week, I took the exam for Microsoft Certification 70-486: Developing ASP.NET MVC 4 Web Applications and passed successfully and scored 831. This was my first exam after almost two years. Although, the exam format and questions’ style did not differ, I certainly noticed some differences.

The number of questions were 45, and the questions were spread in proportion:

22 general questions
23 questions in 3 different scenarios

The test included 3 different scenarios to analyze, and it required a good amount of time to spend on reading code and business requirements of the scenarios in order to be able to answer the questions. Although the scenarios were quite different, it was very easy to mix the requirements, so a good focus had to be put to remember the requirements of each scenario.

The questions were practical, but not easy. They were focused on details of specific features. I was introduced with good amount of questions regarding session management, especially in distributed environments, security implementation, debugging, azure deployment, and related to controller implementation.

To anyone who is preparing to take the exam, my recommendation is to put a focus on the topics above mentioned.

I hope this helps.

There is life beyond jQuery

I am a huge fan of jQuery library. For years, jQuery has been my ultimate tool for client side development, and I have used it in any web project I have undertaken. Few weeks ago, I took a project to develop a simple brochure style web site, which had to display a couple of static data, and I decided it to be a Single Page Application (SPA) for the sake of the simplicity and reuse of the page templates.

At the beginning, my idea was to do the dom manipulation with jQuery and templating using jsRender library, but during the planning phase, I thought I should take into consideration using a SPA framework or library. I did a little research on the web, consulted a friend of mine, and then shortened my list to DurandalJS and AngularJS. After giving a quick try to each of them, I decided to go with AngularJS.

Using HTML templates for pages and binding data to the templates was dead simple in AngularJS. The biggest implementation challenge on the project was the internationalization, as the site is multilingual in four different languages. With the help of Angular translate module I managed to translate the labels very easily, and by extracting the language using route params I made the app to decide on the language of controler. The app worked like a charm.

On overall, I managed to finish the whole project within three working days and the most interesting part for me was that I managed to do it without using jQuery at all. Ever since I have started to use jQuery, this is the first project that I have finished without using jQuery. I still think that jQuery is an amazing library and I will continue using it in the future, but there is one other thing, that certainly, I will start using more and more AngluarJS as well.

Multiplatform development with Phonegap

It has been a while not being active in blogging. I have been engaged in a project developing mobile applications for a tourism project in Kosovo. The project entailed development of three mobile applications for the needs of the project in three major platforms, iOS, Android, and Windows Mobile.

As the requirements were to develop the very same functionality and look in all platforms, the first thing that came to my mind was to use in HTML5, CSS3, and JavaScript combination. I would share the same code and design in three different platforms and finish the project in a faster time.  After a short analysis and readings, I came to decision to use jQuery mobile and PhoneGap. Now that everything is finished, I would like to describe my experience here so you can make a better judgement when you start your own project.

Goods

The initial start of the project was a fairytale. I managed to customize the jQuery mobile theme and adjust the design as needed and created the prototype within a week. It was a nice piece which satisfied the needs of my client. I used the PhoneGap build which made my job easier. There was no need to install anything and was using a text editor to write HTML + CSS + JavaScript code.

PhoneGap is an excellent tool to build non-native applications in an amazingly fast way. Our application was a basic brochure which did not require a native experience and HTML5 app was doing a great job.

Leverage existing knowledge

Leveraging existing knowledge was the main motivation behind going non-native development. My experience in designing and developing web applications was a great help in immediately starting to develop the applications.

Shared functionality

Although I managed to port around 70% of the functionality in all three platforms, the idea of write once run anywhere is a fallacy. I faced the most problems when porting to Windows Phone. The browser was not rendering well the look and feel and had to do some custom tricks to adopt. Also there was a bug with back button event in jQuery mobile which was not reacting well to Windows Phone back button event. Apple iOS and Android platforms were working fine with minimal differences.

Easier maintenance

Maintenance is a huge cost factor in the lifecycle of an application, and mobile applications make no exception on this. Having the same codebase made changes easier and faster. After deploying the first version, we saw the need to some updates, and having to touch same JavaScript or HTML code made propagation of changes to other platforms a matter of copy – paste.

Bads

After putting some images to the application, the application soon passed the size of 35 megs. PhoneGap build does not support applications larger than 15 MB. As my app was larger I had to build them locally. This required separate installations of mobile development platforms and the PhoneGap build itself, and required to have a Windows PC and Mac computer.

Some performance issues

PhoneGap and jQuery mobile is a good combination, but, there are some performance implications though. It is not hard to notice some latencies on clicks. There are some performance improvement tips and tricks out there, but you have to do a little research and customizations to achieve a desired performance level.

Overall opinion

In general, my experience developing these applications was OK. I managed to create three applications within a month and a half, which deadline, I’m sure I would not be able to meet if I would have chosen to develop in native platforms. Depending on the requirements, if there is no need for a very fast application, such as games or any real time communication application, I would recommend  PhoneGap. When it comes to jQuery mobile, on my next project I will test another framework first and then post my recommendation 🙂

JSONP request to your WebAPI service

A day ago, I was trying to prepare a demo on how simple it is to make a cross domain AJAX request to a web service, and display the JSON result in a friendly HTML div using jQuery AJAX method.

I created a simple WebAPI controller, which had a method which returns a IEnumerable<MyObject> of a list of objects, and published it to a Windows Azure Cloud Service. The Web Service was working like a charm.

When I created the jQuery code, which was as simple as this

$(function () {
var url = "http://webprogramming.cloudapp.net/api/Kompanite?callback=?"

$.getJSON(url, function (data) {
$.each(data, function (index) {
//place info in a div
});
});
});

and was supposed to work smoothly. But, as opposed to a working code, I started to receive no results. I started to catch ajax errors, and saw that the callback function was not being called. After three hours of research, I came through this “JSONP with ASP.NET WebAPI” StackOverflow question, which explained everything. The answer was that, by default, the result of WebAPI was not prepared to deal with callback required for JSONP. You need to have a special JsonMediaTypeFormatter which can handle this kind of situation. After I copied/pasted the formatter class from the answer, and cofigured it in Global.asax’s Application_Start() method through this line:

config.Formatters.Insert(0, new JsonpMediaTypeFormatter());

the jQuery code started to work like a charm. So… if you fall into a similar situation, please make sure you implement your own JsonMediaTypeFormatter to support JSONP calls to your web service.

Social Innovation Camp Kosovo

Last weekend, I had the pleasure and opportunity, to be mentoring for the second Social Innovation Camp Kosovo, together with Dan McQuillan, Fisnik Ismaili, Laura HahnPeter Manning, and Josh Harvey .

 

During a 48 hours challenge, six groups of young Kosovars tried to make reality the idea they had proposed, which intended to make a social impact in Kosovo. After 48 hours of hard work and fun, teams came up with the prototypes of their ideas, went out to test their prototypes with other people, and then presented their prototype together with the impressions gathered outside, in front of the independent judge panel.

After all the fun and hard work, three teams excelled and won prices to continue forward their ideas. The winners were:

  • Eventor – A project which intends to put together events and scholarships for Kosovars, and make them available for students and others to get informed.
  • KapLexo – An idea around book exchanging for second hand books, while making also possible for people to review, comment, meet and discuss, about the books they like and have read.
  • ParkingLot – An idea which intends to make free parking slots in maps (web and mobile) through social participation.

Personally, I would like to thank UNICEF Innovation Labs Kosovo for making this event possible, which creates opportunities for young people to start new projects which could have positive impact in Kosovo.