Essential GWT: Developing Your Application
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.
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.
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.
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