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Essential GWT: Developing Your Application

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What kind of applications should you develop with GWT? How can you go about it? And, why would you use GWT? Federico Kereki answers these questions in this introduction to his book.
This chapter is from the book

Why would you use GWT? What can you develop with it and how? Before delving into specifics (as we'll be doing in the rest of the book) let's consider the answers to these questions, so you'll know what to focus on.

Developing applications with GWT can be seen as a straightforward job, but you should ask some interesting questions to unlock the way to powerful, distinct, applications. What kind of applications should you develop with GWT? (And, given the current push for Cloud Computing, you can even add "Where would you deploy your application?") How can you go about it? And, why would you use GWT?

Let's consider all these questions in sequence to start you on your way through this book, knowing your goal and the road to it.

Rich Internet Applications

When you start reading about Rich Internet Applications (RIAs), your JAB (Jargon, Acronyms, and Buzzwords) warning should go off because there are many words that are bandied about, without necessarily a good, solid definition or a clear delimitation of their meanings.

Basically, what we build are web applications that have the look and feel of classic desktop applications but that are delivered (and "installed") over the web. Many tools have been used for this purpose, such as Java (through applets), Adobe Flash, and more recently, Microsoft Silverlight, but used in this way, all these tools are beaten, in terms of practicality, by simple HTML-based systems.

The RIAs that we will be developing are based on JavaScript and Ajax and just require an appropriate browser to run. Classic web applications were developed with a different set of tools, subjected the user to frequent waits (the hourglass cursor was often seen), and had severe restrictions as to usability, with a much clunkier feel to them than desktop installed programs.

Although some people distinguish between RIAs and the kind of interactive web applications we build, the frontiers are getting blurrier and blurrier. You could argue that Flash or Silverlight require preinstalled plugins, or that development runs along different lines, but in terms of the final result (which is what the user experiences) differences are not so marked, and well-designed HTML/JavaScript/Ajax applications can compete for equality with applications developed with the other tools. (Also, some people opine that HTML 5 can seriously challenge Flash, up to the point of making it obsolete, but that's still to come.1) There used to be obvious differences—the ability to store local data at the user's machine was the biggest one—but tools such as Google Gears or current developments in HTML 5 have provided this feature to web applications.2

Given its ubiquity (from desktops to netbooks, and from cell phones to tablet PCs) the browser can be considered a universal tool, and Ajax provides the best way for the creation of highly interactive applications. Of course, a few years ago there weren't many tools for doing this (GWT itself appeared in 2006) and creating heavy-lifting interactive code with just JavaScript wasn't (and still isn't) an appealing idea.3

Furthermore, given that users have been subjected for many years to web applications, and are familiar with their idioms, you are a bit ahead in terms of user interface design by keeping to a reasonable standard.

As for the language itself, using Java as a tool—even if it gets compiled into JavaScript, as GWT does—provides both a way around JavaScript's deficiencies and introduces a widely used language with plenty of development tools, which has been used over and over for all kinds of applications and has been proved to scale to large-sized applications.4

Web 2.0

Web 2.0 is another expression that has been bandied about a lot since its invention in 2004. Though there are way too many definitions for it, most seem to agree on the idea of using the "Web as Platform," where all applications run in a browser instead of being preinstalled on your desktop. Furthermore, the idea of allowing users to produce their own contents (à la Wikipedia) is also included, highlighting the collaborative aspect of work, and thus bringing into the fold all kind of community and social networking sites (think Facebook or YouTube). Finally (and that's what actually works for us) the concept of mashing together different data sources (probably from many web services) is also included.

GWT applications can obviously be used for producing highly interactive people sites, but they can also link together information from different origins, consuming web services with no difficulty, either connecting directly to the server or by means of proxy-based solutions. Various data formats are also not a problem; if you cannot work with such standards as XML or JSON, you can include external libraries (or roll out your own) through JSNI or Java programming. (We cover this in Chapter 8, "Mixing in JavaScript," and Chapter 9, "Adding APIs.")

In this context, the phrase Service-Oriented Architectures (SOA) frequently pops up. Instead of developing tightly integrated, almost monolithic, applications, SOA proposes basing your systems on a loosely integrated group of services. These services are general in purpose and can be used in the context of different applications—and, as previously mentioned, GWT is perfectly suited to "consuming" such services, dealing with different protocols and standards. (We'll cover this in Chapter 6, "Communicating with Your Server," and Chapter 7, "Communicating with Other Servers.") If your company is centered on an SOA strategy, your GWT-developed applications will fit perfectly well.

Cloud Computing

Next to the idea of using the browser as the basis for the user's experience, the most current term related to modern application development is Cloud Computing. This idea reflects the concept of sharing resources over the web, on demand, instead of each user having a private, limited pool of resources. In this view, software is considered a "service" (the acronym SAAS, which stands for "Software as a Service," is often used) and a resource similar to more "tangible" ones as hardware.

(As an aside, the vulnerability of some operating systems, most notably Windows, to viruses, worms, and similar attacks, has given a push to the idea of using a simple, secure, machine and storing everything "on the web," letting the cloud administrators deal with hackers and program infections.)

For many, this concept is yet another cycle going from centralized resources (think mainframes) to distributed processing (PCs, possibly in client/server configurations) and now to having the web as your provider. The main requirements for such an architecture involve reliable services and software, delivered through specific data centers, and running on unspecified servers; for the user, the web provides an access to a cloud of resources.

For GWT applications, your applications are basically destined from the ground up to be used "in the cloud" because of the standard restrictions imposed by browsers. Distributing an application over the web, accessing it from anywhere, and having your data stored in a basically unknown place are all characteristics of any applications you might write.5

The "Death of the Desktop"

The trend toward Cloud Computing has even spawned a new concept: the "Death of the Desktop." This presents rather starkly the problem of going overboard, to the limit: From the appearance of mini netbooks (with flash-based disks, slow processors, not much RAM) and iPhone-look-alike cell phones, some have reached the conclusion that desktop applications (and even desktop computers!) are on their way out. If this were true, it could be great for GWT developers, but things are a bit different.

Despite several impressive opinions and pronouncements from people all over the industry, the trend toward more powerful machines, with CPUs, memory, and I/O facilities that put to shame the supercomputers of just a few years ago, doesn't seem to be slowing down. Even if you are enamored with the latest netbooks or high-powered cellphones, you should accept that working all the time with minimal screens isn't the way that things can get done at a company. (And for gaming or graphic-intense usages, small machines aren't so hot either; they may do, however, for business-oriented applications.) In any case, GWT can help you because you can use its layout facilities and CSS styling to produce applications for just about any device out there.

Also, remove the rosy glasses for an instant. Cloud computing offers several advantages (and GWT applications can be considered to be right in the middle of that concept) but also presents problems, so you need to plan accordingly. Aside from the obvious difficulty of dealing with possibly flaky web connections, security and compatibility can be stumbling blocks. (On the other hand, scalability is well handled; there are plenty of large sites, with hundreds or thousands of servers, proving that web applications can scale well.) The important point is, with or without desktops, GWT provides some ways around these kind of problems, and we'll study this in upcoming chapters.6

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