Some Pragmatic Flex/Java Considerations

Cool technologies come and go. Only some of them settle down in the toolbox of a professional programmer working on enterprise business applications. The technical excellence of any software is important, but it's not the only component in its success.

The Learning Curve: Reuse of Skills and Code

One important concern of any development manager is the availability of a large pool of people who know a particular software. There are plenty of Java programmers with the skills required to develop Web applications, and the good news is that enterprise Java developers with servlet/Java EE programming skills or Java Swing experience will find the Flex path very easy.
Java and ActionScript 3 are very similar; Eclipse is a familiar environment for many Java developers. Since Flex piggybacks on Java EE and browser technologies, a server-side Java programmer should be able to correlate his current skills with the development process in Flex. Java Swing developers will instantly spot similarities to Java event and layout models. In our experience, the typical ramp-up time for motivated Java developer is two weeks. The best part is that Flex seamlessly integrates with existing Java server code of any flavor - POJO, EJB, Hibernate/Spring, or JMS, so the server-side part can literally remain unchanged.

Application Security

Another important consideration is the security of Flex/Java applications. Flex server-side security management is quite extensive, and it lets you use either container offerings or custom security providers via declarative XML binding. There are a couple of challenges since Flex supports multiple protocols, so Java EE security that relies only on HTTP sessions has to be extended, but it's a simple and well-documented process. On the client side, it builds on Flash Player security that's known for its lack of serious security flaws. You have a built-in security manager that has all the standard protection for cross-domain and zone access. Corporations can further restrict the code they get from third parties by wrapping the code loaders in additional security managers.
Flex GUI Performance
Java Swing is a tried and true tool for developing responsive GUIs in demanding applications like stock trading and online auctions. Flex is capable of providing near-real-time data rendering to the GUI and very high refresh rates on large data sets. Flash Player 9 is the high-performance modern virtual machine with precompiled optimized code and a just-in-time (JIT) machine code compiler.

Shorter Development Cycle

It's very possible to build the client side of a real-time portfolio display integrated with news feeds and graphs in about 200 lines of Flex 2 code. A similar Swing program (even if it's created with commercial IDEs) would be several times larger.
A decent Flex developer should be able to prototype (short of server processing) most of the UI for a specific trading system by the end of the first week. If you're lucky and system integration went okay, you can add the collaboration features and multimedia - with the total client code base for the whole project coming within 1,000-1,500 lines. This is definitely not possible with Swing. Of course, some people will say modern Java IDEs generate lots of boilerplate code automatically, but this is still the code that someone has to read, understand, and fix if needs be.
Having said all this, there is a big difference between an application prototyping and delivering a final product - you still need to write code, create new components extend ActionScript classes and implement interfaces. Flex is not a magic wand.

Flex: Room for Improvement

While many programmers who dealt with previous versions of Flex are really happy now that they have a professional Eclipse-based IDE, Java programmers are spoiled by the variety of excellent and responsive IDEs. Flex Builder helps a lot  in writing Flex code, but it's not as sofisticated and elegant as it could have been. It's even not as good as its daddy Eclipse.

While you can use Flex just to connect to your existing applications written as JSP or any other HTTP-compatible technologies, you'll get performance gain if you'll use Flex remoting and messaging that is build on fast Adobe proprietary protocols called AMF3 and Real Time Messaging Protocol (RTMP).  To take advantage of these benefits you have to purchase Flex Data Services licenses, while may not be affordable for small businesses.

Connection Management

Flex provides an extensive infrastructure for managing connections between the Web browser and the server. It lets you specify all the protocol details for the RTMP, HTTP, HTTPS as well as plain socket connections. You can then specify the order in which the protocols should be tried due to availability/firewall issues. You also get alternative real-time push or pull connections on additional protocols, a direct socket API, and tons of low-level hooks that let you build any protocol you want.

Flex and Agile Development
 
In mid-‘90s PowerBuilder and Visual Basic were the tools of choice in the client/server field. Software developers didn't really worry about what was under the hood, but more importantly, they were business users' best friends. They could do stuff quickly, or using the modern jargon, they were agile programmers without even knowing it. They'd ask the business user Joe, "How do you usually do your business? What would you like to have on this screen? Describe the steps of your business process." Most likely Joe wouldn't know all the answers, but this was okay, because developers could come back to the user the next day with a working prototype. This was easy with PowerBuilder's DataWindow. When Joe-the-user saw the prototype, his glassy look all of a sudden would become friendly and understanding. Now Joe was back in control: "No, you did this part wrong, I wanted it different." No problem, developers would return with the changes the next day (not next month, but the next day!).
 Developers didn't really know how DataWindow worked, but they trusted this component. PowerBuilder used event-driven programming model, which was clean and simple. Object A triggers event XYZ on object B, and this event can carry a payload - the data that object B needs to operate. Using modern jargon it's called Inversion of Control or Dependency Injection design pattern. What's important is that the object B doesn't know about object A. On the same note, if object B needs to return the result of some internal function back, it would broadcast this result "to whom it may concern" by triggering one of its own events. This is loose coupling in action.
 The mentality of many Java programmers was different. They'd assign lower priority to the user's windows and spend most of their time designing a multi-tier system that didn't depend on any specific look-and-feel and could be universal. Meetings with Joe would be rare because they couldn't create a decent prototype fast. Fancy IDEs with GUI designers like Matisse weren't in the picture yet and, more importantly, Java programmers were thinking big: UML, design patterns, application servers, and clustering. They enjoyed the programming process for itself. They didn't like the mindset of old-fashioned PowerBuilder or Visual Basic programmers who were thinking windows and screens.
 With Flex you started to care about the business users again. You can change the prototype twice a day, and Joe can do the same with his business requirements. No pile of project documentation is needed. The napkin is back and it works. Flex architects can give the server-side Java team the final okay only after Joe is 100% happy.
 Besides, with Flex we can have the best of both worlds: the source code of the Flex framework is available, we can learn how it works inside, and override some functionality with what suits our needs better.
 Working with Flex promotes agile development, where the people we build the software for are the driving force. Agile development methodology suggests minimizing each development cycle to mitigate the risk of delivering something to the users that they don't want. Agile development encourages frequent face-to-face meetings with the end users as opposed to preparing and sending documents back and forth.

Summary

This quick overview of major RIA-enabling technologies and various approaches to making Web applications richer. It's by no means a complete list: new commercial and open source RIA frameworks and components arise every day.  Regardless of what RIA tools you are going to select, start your evaluations now to get a competitive edge.

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