|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.
SYS-CON Events announced today that Outlyer, a monitoring service for DevOps and operations teams, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Outlyer is a monitoring service for DevOps and Operations teams running Cloud, SaaS, Microservices and IoT deployments. Designed for today's dynamic environments that need beyond cloud-scale monitoring, we make monitoring effortless so you ...
Mar. 27, 2017 02:15 AM EDT Reads: 4,131
My team embarked on building a data lake for our sales and marketing data to better understand customer journeys. This required building a hybrid data pipeline to connect our cloud CRM with the new Hadoop Data Lake. One challenge is that IT was not in a position to provide support until we proved value and marketing did not have the experience, so we embarked on the journey ourselves within the product marketing team for our line of business within Progress. In his session at @BigDataExpo, Sum...
Mar. 27, 2017 01:45 AM EDT Reads: 2,875
Keeping pace with advancements in software delivery processes and tooling is taxing even for the most proficient organizations. Point tools, platforms, open source and the increasing adoption of private and public cloud services requires strong engineering rigor - all in the face of developer demands to use the tools of choice. As Agile has settled in as a mainstream practice, now DevOps has emerged as the next wave to improve software delivery speed and output. To make DevOps work, organization...
Mar. 27, 2017 01:15 AM EDT Reads: 1,809
DevOps is often described as a combination of technology and culture. Without both, DevOps isn't complete. However, applying the culture to outdated technology is a recipe for disaster; as response times grow and connections between teams are delayed by technology, the culture will die. A Nutanix Enterprise Cloud has many benefits that provide the needed base for a true DevOps paradigm.
Mar. 27, 2017 12:45 AM EDT Reads: 2,001
What sort of WebRTC based applications can we expect to see over the next year and beyond? One way to predict development trends is to see what sorts of applications startups are building. In his session at @ThingsExpo, Arin Sime, founder of WebRTC.ventures, will discuss the current and likely future trends in WebRTC application development based on real requests for custom applications from real customers, as well as other public sources of information,
Mar. 27, 2017 12:30 AM EDT Reads: 822
China Unicom exhibit at the 19th International Cloud Expo, which took place at the Santa Clara Convention Center in Santa Clara, CA, in November 2016. China United Network Communications Group Co. Ltd ("China Unicom") was officially established in 2009 on the basis of the merger of former China Netcom and former China Unicom. China Unicom mainly operates a full range of telecommunications services including mobile broadband (GSM, WCDMA, LTE FDD, TD-LTE), fixed-line broadband, ICT, data communica...
Mar. 27, 2017 12:00 AM EDT Reads: 3,321
With the introduction of IoT and Smart Living in every aspect of our lives, one question has become relevant: What are the security implications? To answer this, first we have to look and explore the security models of the technologies that IoT is founded upon. In his session at @ThingsExpo, Nevi Kaja, a Research Engineer at Ford Motor Company, will discuss some of the security challenges of the IoT infrastructure and relate how these aspects impact Smart Living. The material will be delivered i...
Mar. 26, 2017 09:45 PM EDT Reads: 2,038
Apache Hadoop is emerging as a distributed platform for handling large and fast incoming streams of data. Predictive maintenance, supply chain optimization, and Internet-of-Things analysis are examples where Hadoop provides the scalable storage, processing, and analytics platform to gain meaningful insights from granular data that is typically only valuable from a large-scale, aggregate view. One architecture useful for capturing and analyzing streaming data is the Lambda Architecture, represent...
Mar. 26, 2017 08:30 PM EDT Reads: 6,116
As organizations realize the scope of the Internet of Things, gaining key insights from Big Data, through the use of advanced analytics, becomes crucial. However, IoT also creates the need for petabyte scale storage of data from millions of devices. A new type of Storage is required which seamlessly integrates robust data analytics with massive scale. These storage systems will act as “smart systems” provide in-place analytics that speed discovery and enable businesses to quickly derive meaningf...
Mar. 26, 2017 07:45 PM EDT Reads: 9,586
Your homes and cars can be automated and self-serviced. Why can't your storage? From simply asking questions to analyze and troubleshoot your infrastructure, to provisioning storage with snapshots, recovery and replication, your wildest sci-fi dream has come true. In his session at @DevOpsSummit at 20th Cloud Expo, Dan Florea, Director of Product Management at Tintri, will provide a ChatOps demo where you can talk to your storage and manage it from anywhere, through Slack and similar services ...
Mar. 26, 2017 06:45 PM EDT Reads: 4,263
SYS-CON Events announced today that Ocean9will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Ocean9 provides cloud services for Backup, Disaster Recovery (DRaaS) and instant Innovation, and redefines enterprise infrastructure with its cloud native subscription offerings for mission critical SAP workloads.
Mar. 26, 2017 06:30 PM EDT Reads: 2,049
The taxi industry never saw Uber coming. Startups are a threat to incumbents like never before, and a major enabler for startups is that they are instantly “cloud ready.” If innovation moves at the pace of IT, then your company is in trouble. Why? Because your data center will not keep up with frenetic pace AWS, Microsoft and Google are rolling out new capabilities In his session at 20th Cloud Expo, Don Browning, VP of Cloud Architecture at Turner, will posit that disruption is inevitable for c...
Mar. 26, 2017 05:00 PM EDT Reads: 2,141
SYS-CON Events announced today that SoftLayer, an IBM Company, has been named “Gold Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. SoftLayer, an IBM Company, provides cloud infrastructure as a service from a growing number of data centers and network points of presence around the world. SoftLayer’s customers range from Web startups to global enterprises.
Mar. 26, 2017 02:30 PM EDT Reads: 1,784
SYS-CON Events announced today that Conference Guru has been named “Media Sponsor” of SYS-CON's 20th International Cloud Expo, which will take place on June 6–8, 2017, at the Javits Center in New York City, NY. A valuable conference experience generates new contacts, sales leads, potential strategic partners and potential investors; helps gather competitive intelligence and even provides inspiration for new products and services. Conference Guru works with conference organizers to pass great dea...
Mar. 26, 2017 02:15 PM EDT Reads: 4,380
SYS-CON Events announced today that Technologic Systems Inc., an embedded systems solutions company, will exhibit at SYS-CON's @ThingsExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Technologic Systems is an embedded systems company with headquarters in Fountain Hills, Arizona. They have been in business for 32 years, helping more than 8,000 OEM customers and building over a hundred COTS products that have never been discontinued. Technologic Systems’ pr...
Mar. 26, 2017 02:00 PM EDT Reads: 3,390
SYS-CON Events announced today that CA Technologies has been named “Platinum Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY, and the 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CA Technologies helps customers succeed in a future where every business – from apparel to energy – is being rewritten by software. From ...
Mar. 26, 2017 01:45 PM EDT Reads: 1,842
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend @CloudExpo | @ThingsExpo, June 6-8, 2017, at the Javits Center in New York City, NY and October 31 - November 2, 2017, Santa Clara Convention Center, CA. Learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
Mar. 26, 2017 01:45 PM EDT Reads: 8,511
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 20th International Cloud Expo, which will take place on June 6–8, 2017, at the Javits Center in New York City, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
Mar. 26, 2017 01:15 PM EDT Reads: 2,128
SYS-CON Events announced today that Loom Systems will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Founded in 2015, Loom Systems delivers an advanced AI solution to predict and prevent problems in the digital business. Loom stands alone in the industry as an AI analysis platform requiring no prior math knowledge from operators, leveraging the existing staff to succeed in the digital era. With offices in S...
Mar. 26, 2017 12:45 PM EDT Reads: 1,324
SYS-CON Events announced today that Interoute, owner-operator of one of Europe's largest networks and a global cloud services platform, has been named “Bronze Sponsor” of SYS-CON's 20th Cloud Expo, which will take place on June 6-8, 2017 at the Javits Center in New York, New York. Interoute is the owner-operator of one of Europe's largest networks and a global cloud services platform which encompasses 12 data centers, 14 virtual data centers and 31 colocation centers, with connections to 195 add...
Mar. 26, 2017 12:30 PM EDT Reads: 1,137