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John Bennett
Macromedia
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While working on the Blackboard project, we
encountered several major discoveries about
how to build Rich Internet Applications. Our
findings were based on solutions and real-world
implementations, rather than inventing new approaches
from scratch.
Although these lessons may not seem revolutionary,
they are common sense principles that any developer
can and should employ in developing Rich Internet
Applications for the web with Macromedia MX.
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| Wherever
possible, put data and logic on the server |
| Macromedia
Flash MX creates new alternatives for solution architecture.
ActionScript gives the thin client a rich, extensible, object-oriented
programming environment. Macromedia Flash Remoting makes
it easy to distribute data and programs between client and
server. We used the following best practices guidelines
to decide how to structure our data and logic layers. |
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| The following
rules of thumb emerged in working on the Blackboard project
and another similar project: |
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Wherever
possible, place both the data and logic on the server.
Only send data for display to the client. The only logic
on the client should be that which is required to implement
the user interface. Any other data and logic should
only be put on the client as an exception to the rule,
whenever it is required for a specific solution. |
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Take advantage
of locating (or caching) data on the client for your
application when possible. Similarly, if the user interface
(UI) will benefit from logic that is implemented on
the client, then put the logic on the client. Do not
be reluctant to place logic and data on the client it
is advantageous and possible. The client-side software
is what makes a rich user experience possible. |
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| The rationale
for these guidelines include: |
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Programmer
productivity is higher for server-side code. Many factors
contribute to this relationship. The Java compiler eliminates
many types of programming errors early in the development
process. Other tools, such as integrated development
environments, debuggers, unit-testing frameworks, and
code profilers, can aid the Java programmer’s
work. |
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A rich set
of libraries exists for server-side code. In addition
to what is integral to the Java language, a vast array
of extensions are available for building Java solutions. |
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The quality
assurance (QA) process for server-side components is
easier. For example, it is relatively straightforward
to build a test harness for Java components. |
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Server-side
code is not subject to reverse engineering, unlike client
logic, which is sent over the network. Algorithms that
are considered valuable intellectual property should
be implemented on the server—unless there is a
compelling reason to do otherwise. |
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| The Macromedia
Flash component reuse model is different |
A variety of user
interface components are available for Macromedia Flash MX.
Most of these components are free. Component source code is
readily available in the Macromedia MX authoring environment.
Plan to examine this source code. (It is compact and easy
to understand.) Often this is the best way to learn precisely
what capabilities each component offers. In some cases, you
may want to reuse code from these
components. You may even choose to clone and modify these
components to get the behavior you require.
For example, in order to get a draggable
list box on Blackboard, we copied and modified the
ListBox component and several of its collaborators. See the
article entitled The
Blackboard Group Management application: Realizing rapid development
with Macromedia Flash MX for details. |
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| Acquire
Macromedia Flash and ActionScript development expertise |
| Macromedia Flash
MX is an extraordinarily powerful tool for building Rich Internet
Applications. As with other programming environments, consult
with experts if you want to get the most out of it. You can
hire expertise, or you can cultivate it with internal resources.
If you plan to acquire Macromedia Flash expertise by training
developers within an existing team, you should realize that
using Macromedia Flash encompasses much more than merely learning
how to use a new software interface. It has its own concepts,
tools, and development methods. Like the developer with procedural
programming experience learning object-oriented development—it
takes time to learn how to think in a different way. It is
unreasonable to expect a Java coder to become proficient with
Macromedia Flash after just a few days of self-study. |
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| Utilize
available tools |
| To save time,
learn about the following tools: |
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Macromedia
Flash debugger
The Macromedia Flash debugger is a valuable resource for diagnosing
errors in your Macromedia Flash applications. You can set
break points in included files. Time spent learning this tool
will save you time. |
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NetConnection
debugger
This essential tool shows information that flows between the
Macromedia Flash client and the server(s) with which it communicates. |
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Macromedia
Flash debug player
The debug player helps you diagnose problems that show up
during integration testing when the Macromedia Flash UI program
is not being launched from the Macromedia Flash MX authoring
tool. Note that you may have to install the debug player,
in which case, you must first uninstall the release player.
Read about the Debug
version of Macromedia Flash Player for more information. |
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| Use component-based
development to eliminate bugs early |
It is better
to find and fix bugs early in the development cycle, when
system components can be tested in isolation than during
system integration, where finding and fixing bugs are much
more costly. While this is true in any software system,
it is particularly true in a rich UI solution because of
the inherent complexity of the infrastructure on which such
a solution runs.
Therefore the most expedient approach to developing a rich
UI application involves using component-based designs, well-defined
subsystem interfaces, and thorough unit testing. The early
investment in this approach really brings a big return on
investment, helping you to avoid time consuming late stage
problems.
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| The Blackboard
project illustrates this approach in several ways. First,
we created prototypes, putting the UI design through rigorous
tests before finalizing the interface—making sure
to separate client and server subsystems. Then, we
built test harnesses on either side of the interface. Later,
we completed the more time consuming development of client
and server components in parallel. See the article Designing
Java applications for Flash Remoting for more information.
Pay particular attention to the section that discusses how
Java interface technology enables easier parallel development. |
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The BBGM client
was also designed as separate component. Each component
was built and tested separately. Each had its special-purpose
test programs. The client was not assembled (integrated)
until its components had been fully implemented and unit
tested.
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John Bennett is an architect in the newly formed Macromedia
Strategic Services group (also known as the SWAT team).
The SWAT team acts as a catalyst for Macromedia MX development
projects with strategic customers and partners, driving
early phase development projects that demonstrate best practices
in Rich Internet Application development. Before joining
Macromedia, John built enterprise software solutions for
financial services companies across the globe.
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