|By Jason Dolinger||
|July 15, 2009 04:00 AM EDT||
With the arrival of .NET 3.5, WPF and the RTM of Silverlight 2, .NET developers have more choices than ever for designing, developing and deploying compelling applications with rich user interfaces. However, there are other mainstream alternatives that don't fall into the .NET camp. When it comes to the RIA world, technologies such as Adobe Flex and Flash may seem more foreign to some of us then driving on the left side of the road would be to an American. However, given the need to work on a Flex project, we are actually quite well suited for the transition, more so in many cases than developers coming from a more traditional web development world.
First off all, why choose to use Flex anyway? If you are building an RIA to deploy through the browser, Silverlight would seem the logical choice for a truly custom and unique UI when ASP.NET and AJAX don't fit the bill. But there are certain situations where an enterprise may decide that going the Adobe route is the correct choice for the needs of a particular project. The primary motivation comes with an application that is being built for external consumers. The Flash plug-in currently has a 99% market penetration according to Adobe and that's hard to argue with. This will be changing as Silverlight continues to be adopted but it currently remains an important consideration. As an example, I was recently involved in building an RIA meant to be subscribed to by many large financial institutions. These types of clients do not typically have the freedom to install browser plug-ins at will. Something like the Silverlight plug-in would need to be deployed in a firm-wide rollout after many months of compatibility testing, while Flash has been standard for years. Aside from this reason, the Adobe AIR runtime makes for a compelling usage scenario where your application assets can be deployed both in the browser or standalone on the desktop, allowing reuse of the majority of the same code base. AIR has a sophisticated web-based deployment and versioning model as well. Some form of this is expected in Silverlight 3 but it is already a reality for AIR. Finally, if you have a set of graphical assets already designed for Flash and designers who are most experienced in this area, the Flash/Flex path may be the easiest way to get the user experience you are after.
If you (or your project manager/architect) have decided that it must be Flex, don't be discouraged. While learning any new platform is a non-trivial undertaking, Flex is not as foreign to .NET as it may seem. When I've conducted interviews for Flex positions, usually the candidate came from a history of Java web development. The Flex platform enjoys close ties with the Java community, from its Eclipse-based IDE, Java style package naming, and Adobe's support of its Livecycle Data Services and BlazeDS APIs for remote service integration. However, I believe that the learning curve is more natural coming from WPF or Silverlight than from Java, culture and IDE differences aside. Rich Internet Applications are closer architecturally to desktop applications written in C++, WinForms or WPF than the standard non-AJAX web application. The kinship between Silverlight and Flash is even closer. RIAs are persistent applications that maintain state, and call remote services to load and store data (usually through XML or JSON), rather than loading pages of HTML. As such, the patterns for architecting one should follow those of a desktop application deployed in an n-tier environment. Further, the major elements of the Flex platform will be quite familiar to any WPF or Silverlight developer. Flex contains an XAML-like markup language for UI layout, an OO language to glue everything together, a mature set of controls and layout panels, an analogous eventing system, databinding, and a DataTemplate like mechanism.
Introducing the Flex 3 Framework
Flex is the UI toolkit for building RIAs based on the ActionScript language and running in Flash player, as WPF and Silverlight are frameworks for building applications in C# that run in the .NET CLR or Silverlight runtime. As WPF has XAML, Flex has its own analogous language called MXML that serves the same purpose. It is a serialization language for describing your application views by constructing trees of layout elements and control elements, and setting properties on them. Your MXML files get compiled to ActionScript and the MXML tags that you declare create instances of AS classes. Flex does not have the same concept of codebehind as you'll find in the .NET world, but ActionScript can co-exist in the same file as your MXML markup in a special CDATA block for this purpose. This ActionScript is just another part of the class that the MXML in the file gets compiled into, so the overall effect is the same.
Many other WPF constructs have similar analogues in the Flex world. Flex provides an eventing model that anyone familiar with C# delegates and events will have no trouble understanding. Routed events have been a part of Flex for as long as they were in WPF. These events have a tunneling phase (called "capture") where they travel down through the control tree from the top level (called the Stage in Flash) to the target where the event occurred, followed by a bubbling phase where they travel up the tree, in both directions, looking for any registered event handlers.
Flex has a databinding mechanism for connecting UI controls to model data. The syntax is more awkward than you may be used to, but you can (and should) still make use of this for binding your view controls to their model (or viewmodel). Unfortunately there is no concept of a DataContext, so even if a single model object provides all of the underlying data for your view, you'll need to specify that in each binding expression path.
For giving a custom look to lists of data as well as DataGrid columns, Flex gives you a construct called an item renderer that is quite similar to our familiar DataTemplate. An item renderer is usually a small tree of MXML, but can be implemented as a class with some behavior behind it. When binding to a list of data, Flex uses the renderer as a factory to create additional instances of the same class, used to render each underlying model item in the list. Just as in XAML, your item renderers can be declared inline, separated out into separate component files or even built up in code. Item renderers in Flex only apply to list data. With the PresentationModel patterns being applied in .NET 3.5 now, views are often being abstracted into a simple ContentControl rendering dynamically based on the DataTemplate for the bound Content, but you won't be able to do anything quite that clever here.
Learning the ActionScript language will present no major hurdle for anyone experienced with C# or Java. ActionScript 3 (the current version) is based on ECMAScript 4.0, and is largely grounded in OO principles with the addition of some ideas from the functional world. It is a true object-oriented language supporting inheritance, polymorphism and interfaces. The language is somewhat more dynamic; however, there are no strongly typed arrays or lists and you can forget about generics. There are no explicit delegates or events (objects fire events by implementing the IEventDispatcher interface). But functions are first class objects that can be passed as method arguments, used most frequently for adding handlers for events. Functions can also be anonymously declared inline. Interestingly, the ActionScript Array class has a number of higher order functions such as forEach(), filter(), map(), and some() for applying a function over a list of elements. If you are already using LINQ extension methods and delegates, you'll have no problem figuring out what to do with these. The language does leave out a few of the common OO constructs that you've grown accustomed to, such as abstract classes, private constructors and static initializers. While you will miss them, they won't be anything that you can't work around.
Flex makes use of the Flash player threading model in which all of the code you write executes on the single UI thread, so forget about doing CPU-intensive processing while keeping your UI responsive. You can perform some I/O bound operations through a model similar to .NET's Asynchronous Programming Model though. Through this mechanism, you schedule an asynchronous action to be executed by the Flash player, such as calling a remote service or reading a file. You provide an event handling function to be invoked when the operation is finished so you can process the results, but this will be invoked on the same UI thread. While this model can be limiting, it does free you from worrying about thread synchronization or the need to marshal data between threads.
Perhaps the most initially disconcerting part of your switch to Flex will be getting used to a new development environment. The FlexBuilder IDE is based on Eclipse, coming either as a standalone install + the Eclipse shell or as a plug-in for existing Eclipse installations. Eclipse is a full-featured IDE when using it for Java development, and you get out of the box a similar feature set to what you have with Visual Studio + Resharper. But FlexBuilder does not support most of the more advanced refactorings, code organization, and generation tools that Eclipse users might be accustomed to. Therefore, you may feel that you are taking a step backwards when making the switch from Visual Studio. Most of your basic debugging tools are present (there are no conditional breakpoints but this is coming in Flex 4).
The story is more fragmented regarding the UI designer/developer workflow. Expression Blend has come a long way toward allowing designers and developers to simultaneously work on the same source tree and have a productive working relationship. Unfortunately there is no equivalent in the Flex world, and no tool that generates MXML, which can build and run the same projects used in Flex Builder. There is a built-in WYSIWYG editor in Flex Builder, but like the XAML designer in Visual Studio, it's not very useful beyond trivial applications. In general the flow between developers and designers is not as natural. Achieving more interesting effects, skins, and animations in Flex is often a combination of handwritten MXML combined with artifacts generated from tools such as Flash IDE, Adobe Illustrator, and open source libraries like Degrafa.
The Server Tier
As mentioned, the Adobe Flex community enjoys close ties with the Java world, and you'll find that a majority of Flex applications are served from and call remote services on a Java application server, or servlet engine. A large reason is that Adobe has released and supported a suite of APIs for integrating Flash Remoting with Java, through its AMF (Action Message Format) binary protocol. These products, BlazeDS and LiveCycle Data Services, provide a framework for exposing Java classes as endpoints for Flash Remoting and you get automatic mapping between your ActionScript and Java domain objects.
However, Flex is not in any way tied to Java, and you can easily serve a Flex application from IIS. Flex's HTTPService class asynchronously consumes XML, JSON or SOAP served from .NET Web Services, REST, or WCF. In this way you'll continue to use your IIS and .NET server infrastructure and skills, perhaps with a thin facade layer to serve the data in the format your Flex application expects. Furthermore, there is an open source implementation of AMF: FluorineFx. It comes complete with framework libraries and wizards for generating and configuring an ASP.NET web application that serves AMF. Writing a remote service for a Flex application becomes little more than writing your class and marking it with the appropriate attributes. I'd highly recommend checking out this option if you want to keep using C# on the server. AMF is more efficient than XML or JSON, and you'll have the power of using strongly typed ActionScript domain objects in your Flex tier without needing to write the mapping layer yourself. Pushing data to the browser is an option with Lightstreamer, RTMP, or sockets with a custom protocol.
Architecture and Design Patterns
As with any platform, architecture and design plays a larger role as the complexity of your application increases. This is one of the places where your existing experience will translate very well, and you'll be better off than Flex developers coming from the web world.
One of the biggest problems we need to circumvent is that of your entire application becoming housed within a few monolithic UI classes. The problem is even worse with Flex because, as mentioned, the code that you write along with your view can be put in a script block right in your MXML markup. This can be greatly abused just as code behind in WPF and other .NET platforms often is. I've seen more than one application consisting of a few grotesquely large MXML files with a few helper classes. Instead we need a way to write our applications in a clean and decoupled manner and achieve a proper separation of concerns.
There are a number of MV-x patterns used to provide basic architectural organization, often Model-View-Presenter for WinForms and Model-View-ViewModel (also called PresentationModel) in WPF. M-V-VM is the choice for WPF (over vanilla MVP) because of the platform's sophisticated databinding framework. As Flex also has a useable binding system, I've successfully applied M-V-VM to a large Flex project. The typical three-layer approach:
Service layer composed of classes that wrap Flash RemoteObjects (when using FluorineFx) or HTTPService classes for JSON or XML transfer. There should be service interfaces for all classes.
ViewModel layer that handles events from the views and exposes bindable properties that present a flat picture of the model data used in the view. These classes get injected with the service classes (of course talking to them through their interface to allow for mocking).
View layer composed primarily of MXML components with a minimum of ActionScript required to glue everything together. The primary purpose of this code is to create the ViewModel instance and direct event handlers from the UI controls into the ViewModel. Code that needs to stay very close to the view (such as drag and drop) can stay here as well.
I like to couple the above pattern with dependency injection to construct and inject instances of the viewmodel classes with their services and any other dependencies. This is still a rare technique in the Flex community, but is becoming more commonplace with several quite useable open source containers out there. SpiceFactory's Parsley and the Spring ActionScript container (formerly known as Prana) are great candidates for this.
Another architectural alternative is the Cairngorm framework, which is the Adobe approved framework for achieving the ideals set out above. You'll find many Flex projects that use it to varying degrees of success and pain. The main features of Cairngorm are a FrontController class with a set of commands that you write to handle the events, a ModelLocator singleton that provides a global access point to your model layer, and a ServiceLocator singleton for looking up instances of Remote Service wrappers. At first glance, Cairngorm feels a lot like a Java Struts MVC style framework (with FrontControllers and Commands), and may trick some more web developers into believing so, but this is not the case.
Cairngorm, like any framework, has some useful constructs and some frustrating ones, and one of the things that makes a framework useful is being able to incorporate the parts you want without making your whole codebase depend on the pieces you don't. While this is not a problem inherent in Cairngorm, many developers new to the framework utilize everything verbatim in the way that the tutorials and how-to's demonstrate. This tends to result in a congested code base with too much boilerplate code for Commands and Delegate classes, and lots of direct dependencies on the ModelLocater and ServiceLocator singletons. As we know that singleton classes are the enemy of flexibility and testability, this should make most of us cringe.
If you decide to leverage Cairngorm or take over a project already using it, remember to apply the good lessons you've learned in the .NET world. ViewModels are still worthy constructs to use with the framework, providing a place for handling events and exposing portions of your model that are local only to your specific component (they can be managed by the ModelLocator). Cairngorm is open source, so you can modify the FrontController to use your IoC container as the factory for your Command classes, so they are injected with the ModelLocator and service instances, rather than using the singleton method of accessing them. The Spring ActionScript container is already incorporating extensions to allow you to work around the messier parts of Cairngorm and is worth a look just for this reason.
As Silverlight and WPF mature and gain mainstream acceptance, Flex and Flash will undoubtedly be forced to evolve in a direction where they can stay competitive. It's likely that there will be further feature swapping and parallels between the two. If you do find yourself in a position where you or your team will need to work on a Flex application, don't feel that you will be throwing away what you know and starting from scratch. Rest assured that you will be in the best possible place to pick up the new framework as well as anyone, and can continue to build on the .NET infrastructure and support that you already have.
|cgehrke 07/09/09 06:30:00 AM EDT|
Thanks for your article. Your points are clearly explained and well thought out. Great job.
I am curious why you don't mention Adobe's latest design tool called Adobe Catalyst which has been in Beta and available for download for months now?
Adobe Catalyst is a new professional interaction design tool for rapidly creating user interfaces without coding.
I have been using Catalyst since December 2008 when I received a copy in Milan at the Adobe MAX Event. It's the perfect tool for merging the design world of Adobe to the developer world of Flex and Flash.
Using Catalyst, a designer can open and retain their artwork in a native format. No conversion or cutting up necessary. Just open your art file (PNG, PSD, AI) and retain your folder structure, effects and layers. You can then begin defining your elements so Flex knows what to do with them (IE: Buttons, Scroll Bars, Navigation, Etc,). Catalyst will write the Flex code for the developer under the hood. At any point you can switch back and forth from design to code view.
Adobe is known for it's great design tools: Photoshop, Illustrator and Fireworks to only name a few. It was only a matter of time until they found a way to merge the design world with the newly acquired developer world of which they adopted from Macromedia only 5 years ago. I am sure we've only seen the tip of the iceberg in regards to Adobe's full potential in the developer world.
Not to take away from your article in anyway, you did a great job here. Thanks for sharing.
Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is expected in the amount of information being processed, managed, analyzed, and acted upon by enterprise IT. This amazing is not part of some distant future - it is happening today. One report shows a 650% increase in enterprise data by 2020. Other estimates are even higher....
Sep. 29, 2016 09:00 AM EDT Reads: 4,161
An IoT product’s log files speak volumes about what’s happening with your products in the field, pinpointing current and potential issues, and enabling you to predict failures and save millions of dollars in inventory. But until recently, no one knew how to listen. In his session at @ThingsExpo, Dan Gettens, Chief Research Officer at OnProcess, will discuss recent research by Massachusetts Institute of Technology and OnProcess Technology, where MIT created a new, breakthrough analytics model f...
Sep. 29, 2016 08:00 AM EDT Reads: 2,089
Internet of @ThingsExpo has announced today that Chris Matthieu has been named tech chair of Internet of @ThingsExpo 2016 Silicon Valley. The 6thInternet of @ThingsExpo will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Sep. 29, 2016 08:00 AM EDT Reads: 2,686
There is little doubt that Big Data solutions will have an increasing role in the Enterprise IT mainstream over time. Big Data at Cloud Expo - to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA - has announced its Call for Papers is open. Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is...
Sep. 29, 2016 08:00 AM EDT Reads: 2,710
DevOps at Cloud Expo, taking place Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long dev...
Sep. 29, 2016 07:00 AM EDT Reads: 3,489
The Internet of Things will challenge the status quo of how IT and development organizations operate. Or will it? Certainly the fog layer of IoT requires special insights about data ontology, security and transactional integrity. But the developmental challenges are the same: People, Process and Platform and how we integrate our thinking to solve complicated problems. In his session at 19th Cloud Expo, Craig Sproule, CEO of Metavine, will demonstrate how to move beyond today's coding paradigm ...
Sep. 29, 2016 07:00 AM EDT Reads: 3,414
Fact is, enterprises have significant legacy voice infrastructure that’s costly to replace with pure IP solutions. How can we bring this analog infrastructure into our shiny new cloud applications? There are proven methods to bind both legacy voice applications and traditional PSTN audio into cloud-based applications and services at a carrier scale. Some of the most successful implementations leverage WebRTC, WebSockets, SIP and other open source technologies. In his session at @ThingsExpo, Da...
Sep. 29, 2016 06:45 AM EDT Reads: 1,675
Cognitive Computing is becoming the foundation for a new generation of solutions that have the potential to transform business. Unlike traditional approaches to building solutions, a cognitive computing approach allows the data to help determine the way applications are designed. This contrasts with conventional software development that begins with defining logic based on the current way a business operates. In her session at 18th Cloud Expo, Judith S. Hurwitz, President and CEO of Hurwitz & ...
Sep. 29, 2016 06:45 AM EDT Reads: 3,209
SYS-CON Events announced today that Roundee / LinearHub will exhibit at the WebRTC Summit at @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. LinearHub provides Roundee Service, a smart platform for enterprise video conferencing with enhanced features such as automatic recording and transcription service. Slack users can integrate Roundee to their team via Slack’s App Directory, and '/roundee' command lets your video conference ...
Sep. 29, 2016 05:45 AM EDT Reads: 1,504
Digital transformation is too big and important for our future success to not understand the rules that apply to it. The first three rules for winning in this age of hyper-digital transformation are: Advantages in speed, analytics and operational tempos must be captured by implementing an optimized information logistics system (OILS) Real-time operational tempos (IT, people and business processes) must be achieved Businesses that can "analyze data and act and with speed" will dominate those t...
Sep. 29, 2016 05:15 AM EDT Reads: 1,246
IoT is fundamentally transforming the auto industry, turning the vehicle into a hub for connected services, including safety, infotainment and usage-based insurance. Auto manufacturers – and businesses across all verticals – have built an entire ecosystem around the Connected Car, creating new customer touch points and revenue streams. In his session at @ThingsExpo, Macario Namie, Head of IoT Strategy at Cisco Jasper, will share real-world examples of how IoT transforms the car from a static p...
Sep. 29, 2016 05:00 AM EDT Reads: 1,643
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo Silicon Valley Call for Papers is now open.
Sep. 29, 2016 04:30 AM EDT Reads: 4,691
The Transparent Cloud-computing Consortium (abbreviation: T-Cloud Consortium) will conduct research activities into changes in the computing model as a result of collaboration between "device" and "cloud" and the creation of new value and markets through organic data processing High speed and high quality networks, and dramatic improvements in computer processing capabilities, have greatly changed the nature of applications and made the storing and processing of data on the network commonplace.
Sep. 29, 2016 04:00 AM EDT Reads: 1,218
Almost two-thirds of companies either have or soon will have IoT as the backbone of their business in 2016. However, IoT is far more complex than most firms expected. How can you not get trapped in the pitfalls? In his session at @ThingsExpo, Tony Shan, a renowned visionary and thought leader, will introduce a holistic method of IoTification, which is the process of IoTifying the existing technology and business models to adopt and leverage IoT. He will drill down to the components in this fra...
Sep. 29, 2016 04:00 AM EDT Reads: 1,822
SYS-CON Events announced today that ReadyTalk, a leading provider of online conferencing and webinar services, has been named Vendor Presentation Sponsor at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. ReadyTalk delivers audio and web conferencing services that inspire collaboration and enable the Future of Work for today’s increasingly digital and mobile workforce. By combining intuitive, innovative tec...
Sep. 29, 2016 03:30 AM EDT Reads: 3,042
I'm a lonely sensor. I spend all day telling the world how I'm feeling, but none of the other sensors seem to care. I want to be connected. I want to build relationships with other sensors to be more useful for my human. I want my human to understand that when my friends next door are too hot for a while, I'll soon be flaming. And when all my friends go outside without me, I may be left behind. Don't just log my data; use the relationship graph. In his session at @ThingsExpo, Ryan Boyd, Engi...
Sep. 29, 2016 03:30 AM EDT Reads: 1,380
SYS-CON Events announced today that Pulzze Systems will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Pulzze Systems, Inc. provides infrastructure products for the Internet of Things to enable any connected device and system to carry out matched operations without programming. For more information, visit http://www.pulzzesystems.com.
Sep. 29, 2016 03:15 AM EDT Reads: 1,910
IoT offers a value of almost $4 trillion to the manufacturing industry through platforms that can improve margins, optimize operations & drive high performance work teams. By using IoT technologies as a foundation, manufacturing customers are integrating worker safety with manufacturing systems, driving deep collaboration and utilizing analytics to exponentially increased per-unit margins. However, as Benoit Lheureux, the VP for Research at Gartner points out, “IoT project implementers often ...
Sep. 29, 2016 03:15 AM EDT Reads: 3,588
There is growing need for data-driven applications and the need for digital platforms to build these apps. In his session at 19th Cloud Expo, Muddu Sudhakar, VP and GM of Security & IoT at Splunk, will cover different PaaS solutions and Big Data platforms that are available to build applications. In addition, AI and machine learning are creating new requirements that developers need in the building of next-gen apps. The next-generation digital platforms have some of the past platform needs a...
Sep. 29, 2016 03:00 AM EDT Reads: 1,895
If you’re responsible for an application that depends on the data or functionality of various IoT endpoints – either sensors or devices – your brand reputation depends on the security, reliability, and compliance of its many integrated parts. If your application fails to deliver the expected business results, your customers and partners won't care if that failure stems from the code you developed or from a component that you integrated. What can you do to ensure that the endpoints work as expect...
Sep. 29, 2016 02:45 AM EDT Reads: 1,721