 | Level: Intermediate Chris Aniszczyk (zx@us.ibm.com), Software Engineer, IBM
David Gallardo (David@Gallardo.org), Software Consultant
17 Jul 2007 Find out about the Eclipse Platform, including its origin and
architecture. Starting with a brief discussion about the open source nature of Eclipse
and its support for multiple programming languages, we demonstrate the Java™ development
environment with a simple programming example. We also survey some of the software
development tools available as plug-in extensions.
This follow-up to David Gallardo's "Getting started with the Eclipse
Platform" offers new information relevant for Eclipse V3.3.
What is Eclipse?
Eclipse is a Java-based, extensible open source development platform. By itself, it is
simply a framework and a set of services for building applications from plug-in
components. Fortunately, Eclipse comes with a standard set of plug-ins, including the well-known Java Development Tools (JDT).
While most users are quite happy to use Eclipse as a Java integrated development
environment (IDE), its ambitions do not
stop there. Eclipse also includes the Plug-in Development Environment (PDE), which is
mainly of interest to those who want to extend Eclipse, since it allows you to
build tools that integrate seamlessly with the Eclipse environment. Because everything
in Eclipse is a plug-in, all tool developers have a level playing field for offering
extensions to Eclipse and providing a consistent, unified IDE for users.
This parity and consistency isn't limited to Java development tools. Although Eclipse
is written in the Java programming language, its use isn't limited to the Java language.
For example, plug-ins are available or planned that include support for programming
languages like C/C++ and COBOL. The Eclipse framework can also be used as the basis for
other types of applications unrelated to software development, such as content management systems.
A great example of an Eclipse-based application is the IBM®
Rational® Software Architect (see Resources), which
forms the basis of IBM's family of Java development tools.
Eclipse is open source
Open source software is software released with a license intended to ensure that
certain rights are granted to users. The most obvious right, of course, is that the
source code must be made available so users are free to modify and redistribute the
software. This protection of users' rights is accomplished with a device called a
copyleft: The software license claims copyright protection and prohibits distribution
unless the user is granted these rights. The copyleft also requires that any
redistributed software be covered by the same license. Since this, in effect, stands
the purpose of copyright on its head — using the copyright to grant rights to
the user, rather than reserve them for the developer of the software — copyleft is often described as "all rights reversed."
Much of the fear, uncertainty, and doubt that has been spread about regarding open
source software involves the so-called viral nature of some copyleft licenses —
the idea that if you use open source software as part of a program you develop, you
will lose your intellectual property because the license will "infect" the proprietary
parts you develop. In other words, the license may require that all software bundled
with the open source software, including any newly developed software, must be released
under the same license. While this may be true of the most well-known copyleft license,
the GNU General Public License (under which Linux®, for example, is released),
there are other licenses that provide a different balance between commercial and community concerns.
The Open Software Initiative is a nonprofit organization that defines what open source
means explicitly and certifies licenses that meet its criteria. Eclipse is licensed
under the OSI-approved Eclipse Public License (EPL) V1.0, which is intended to
facilitate the commercial adoption of Eclipse while being fair to the open source authors.
Those who create plug-ins for Eclipse or who use Eclipse as the basis for a software
development application are required to release any Eclipse code they use or modify
under the EPL, but are free to license their own additions in any way they like.
Proprietary code bundled with software from Eclipse does not need to be licensed as
open source, and the source code does not need to be made available.
Although most will not use Eclipse to develop plug-ins or to create new products based
on Eclipse, the open source nature of Eclipse is important beyond the mere fact that it
makes Eclipse available for no cost (and despite the fact that a commercial-friendly
license means that plug-ins can cost money). Open source encourages innovation and
provides incentives for developers, even commercial developers, to contribute code back
to the common open source-code base. There are a number of reasons for this, but
perhaps the most essential is that the more developers contribute to the project, the
more valuable the project becomes for everyone. As the project becomes more useful,
more developers will use it and create a community around it, like those that have
formed around Apache and Linux. (See Resources for more information about licenses.)
What is Eclipse?
Eclipse is an open source community whose projects are focused on building an open
development platform comprised of extensible frameworks, tools, and runtimes for
building, deploying, and managing software across the life cycle. The Eclipse
Foundation is a not-for-profit member-supported corporation that hosts the Eclipse
projects and helps cultivate an open source community and an ecosystem of complementary products and services.
The Eclipse Project was originally created by IBM in November 2001 and supported by a
consortium of software vendors. The Eclipse Foundation was created in January 2004 as
an independent not-for-profit organization to act as the steward of the Eclipse
community. It was created to allow a
vendor-neutral, open, and transparent community to flourish around Eclipse. Today, the
Eclipse community consists of individuals and organizations from a cross-section of the software industry.
The Eclipse Foundation manages and directs Eclipse's ongoing development. The
foundation provides services to the community, but does not employ the open source
developers (called committers), who actually work on the Eclipse projects.
Eclipse committers are typically employed by organizations or are independent
developers that volunteer their time to work on an open source project.
Now that we've looked at some of the theory, history, and politics behind Eclipse, let's take a look at the product itself.
The Eclipse Workbench
The first time you open Eclipse, you see the welcome page, which exists inside the
workbench (see Figure 1). As an Eclipse user, you'll be given a few options of going to
an overview page, which I recommend (see Figure 2). See what's new, explore some
samples, or go through some tutorials.
Figure 1. Eclipse Welcome Page
Figure 2. Eclipse Overview Page
The Eclipse workbench consists of several panels known as views, such as the
navigator or outline views. A collection of these views is called a perspective.
One of the most common perspectives is the Resource perspective, which is a basic set
of views for managing projects and viewing and editing files in a project.
I recommend most novice users start with the Overview page featured in Figure 2 and
learn about Eclipse. The workbench basics section contains a lot of good starter
information about the various pieces of Eclipse and how they interact. Spend a few
minutes reading the material, then let's dive directly into the Java Development Tools
(JDT) in Eclipse. There's no better way to learn than doing it hands-on.
To continue this short tour of Eclipse, we'll create a a new Java project. Select
File > New > Java Project and enter Hello when
prompted for the project name, then click Finish.
Next, we'll take a look at the Java perspective (if you aren't already there).
Depending on how you like to manage your screen, you can change the perspective in the
current window by selecting Window > Open Perspective > Java or you can
open a new window by selecting Window > New Window and selecting the new perspective.
The Java perspective, as you might expect, has a set of views that are better suited
for Java development. One of these includes, as the top-left view, a hierarchy
containing various Java packages, classes, JARs, and miscellaneous files. This view is
the called the Package Explorer. Also notice that the main menu has expanded to include two new menu items: Source and Refactor.
The Java Development Tools (JDT)
To try out the Java development environment, we'll create and run a Hello World
application. Using the Java perspective, right-click on the Hello project's source
folder (src) and select New > Class, as shown in Figure 3. In the dialog box
that appears, type Hello as the class name. Under Which
method stubs would you like to create? check public static
void main(String[] args), then Finish.
Figure 3. Creating a new class in the Java perspective
This will create a .java file with a Hello class and an empty main() method in the editor area, as shown in Figure 4. Add the
following code to the method (note that the declaration for i has been omitted
deliberately).
Figure 4. The Hello class in the Java editor
You'll notice some of the Eclipse editor's features as you type, including syntax
checking and code completion. Also, when you type an open parenthesis or double quote,
Eclipse will provide its partner automatically and place the cursor inside the pair.
In other cases, you can invoke code completion by using Ctrl+1. Code completion
provides a context-sensitive list of suggestions selectable by keyboard or mouse. The
suggestions can be a list of methods specific to a particular object or a code snippet
to expand, based on various keywords such as for or while.
Syntax checking depends on incremental compilation. As you save your code, it is
compiled in the background and checked for syntax errors. By default, syntax errors are
underlined in red, and a red dot with a white X appears in the left margin. Other
errors are indicated with a lightbulb in the editor's left margin; these are problems
that the editor might be able to fix for you (a feature called Quick Fix).
The code above has a lightbulb next to the for statement
because the declaration for i has been omitted.
Double-clicking on the lightbulb will bring up a list of suggested fixes. In this
case, it will offer to create a class field i, a local
variable i, or a method parameter i; clicking each of these suggestions will display the code that
would be generated. Figure 5 shows the list of suggestions and the code it suggests for a local variable.
Figure 5. Quick Fix suggestions
Double-clicking on the suggestion inserts the code in the proper location in the code.
Once the code compiles without error, you can execute the program by selecting
Run from the Eclipse menu. (Note that there is no separate compilation step
because compilation takes place as you save the code. If your code has no syntax
errors, it's ready to run.) A Launch Configurations dialog box appears, with
appropriate defaults; click Run at the bottom right. A new tabbed panel appears
in the lower panel (the Console), displaying the program's output, as shown below.
Figure 6. Output from the program
You can also run the program in the Java debugger. First, set a breakpoint in main() System.out.println() by double-clicking in the gray margin on
the left side of the editor view, next to the call to System.out.println(). A blue dot will appear. From the Run
menu, select Debug. As described, a Launch Configurations dialog will appear.
Select Run. The perspective will change to the Debug perspective automatically,
with a number of interesting new views, as shown below.
Figure 7. The Debug perspective
Notice the Debug view at the top left of the perspective. This view shows the call
stack and has a toolbar in the title bar that allows you to control the execution of
the program, including buttons to resume, suspend, or terminate the program, step into
the next statement, step over the next statement or return from a method. The panel at
the top right contains a number of tabbed views, including Variables, Breakpoints,
Expressions, and Display. I've clicked Variables so we can see the current value of i.
You can obtain more information about any of the views with the context-sensitive help;
click on the title of the view and press F1.
Additional plug-ins
In addition to plug-ins like the JDT for editing, compiling, and debugging
applications, plug-ins are available that support the complete development process from
modeling, build automation, unit testing, performance testing, version control, and configuration management.
Eclipse comes with a plug-in for working with the open source Concurrent Versions
System (CVS) for source control. The Team plug-in connects to a CVS server, allowing
the members of a development team to work on a set of source-code files without
stepping on each other's changes. Source control from within Eclipse won't be explored
here further because it requires setting up a CVS server, but the capability for
supporting a development team, not just stand-alone development, is an important and integral feature of Eclipse.
Plug-ins supported and hosted by the Eclipse Foundation are found on the
Eclipse Web site. For a more complete list of available plug-ins, go to Eclipse Plug-in Central, which acts as an index for plug-ins.
Eclipse Platform architecture
The Eclipse Platform comes with a powerful set of plug-ins (see Figure 8) that support
projects, such as JDT and the PDE.
Figure 8. Simplified Eclipse Platform architecture
The dark blue pieces signify components that are the core part of
Eclipse's Rich Client Platform (RCP). The concept of RCP itself is outside the scope of
the article, but think of RCP as just a set of plug-ins from Eclipse people can
use to develop applications, such as Lotus Notes® 8. The light blue pieces are
optional (but recommended) pieces to be included in RCP-based applications. And the gray
pieces are completely optional. The platform consists of several components, of which I'll cover several:
-
Runtime
- The runtime is the code that defines Eclipse's plug-in model, based on the OSGi
specification, and notion of extensions and extension points. The runtime also provides additional services like logging and concurrency.
-
JFace/SWT
- The Standard Widget Toolkit (SWT) is the widget set that gives Eclipse its look and
feel. JFace is simply a layer on top of SWT that provides some Model-View-Controller
(MVC) classes to make it easier to develop graphical applications.
-
Workbench
- The workbench gives Eclipse its personality. The concept of views, perspectives, and things like editors are defined at this level.
-
Help (User Assistance)
- The Eclipse component allows you to provide assistance to your users. This can be
done via the help system, which allows users to search for help documentation or through
cheatsheets, which can be thought of interactive task lists for end users.
-
Update
- The update component of Eclipse provides the facilities to allow you to update your applications from version to version.
-
Team
- The team component consists of a framework to allow vendors to plug in their own
version-control systems. An exemplary implementation of a provider is the CVS plug-in
provided out of the box in Eclipse.
Conclusion
From an initial contribution of code from IBM, Eclipse has grown into a full-fledged
open source ecosystem in which more than 100 companies participate. A portable,
extensible open source framework isn't a new idea, but because of its mature, robust,
and elegant design, Eclipse brings a whole new dynamic into play.
Welcome to the Eclipse ecosystem. Our goal was to get you started with the Eclipse
platform quickly. We accomplished this with some introductory text accompanied with a
simple hands-on exercise. Take the knowledge gained from reading this article and
become an active member of the Eclipse ecosystem.
Resources Learn
-
Interested in what's happening inside the Eclipse community? Check out PlanetEclipse.
-
Read the Eclipse Public License V1.0 to learn more about its terms and conditions.
-
Check out the available Eclipse
plug-ins at Eclipse Plug-in Central.
-
Information about open source software, including certified open source licenses, such as
the Eclipse Public License, is available at OpenSource.org.
-
Check out EclipseLive for webinars featuring various Eclipse technologies.
-
Learn more about Rational Software Architect.
-
Eclipse is available under the Eclipse Public License (EPL) V1.0.
-
"Open source
licensing, Part 1: The intent" describes the tenets of copyright and explains the
intents of an open source license. Part 2
explores individual licenses, such as the GNU Public License and the Apache License.
-
Eclipse Plug-in Central is an index
for plug-ins. You can get an RSS feed of the latest plug-ins.
-
The Rich Client Platform (RCP) provides a foundation for building cross-platform applications.
-
Lotus
Notes 8 is built using Eclipse RCP technology.
-
Check out the "Recommended Eclipse reading list."
-
Browse all the Eclipse content on developerWorks.
-
Users new to Eclipse should check out Eclipse project resources' Start Here.
-
Expand your Eclipse skills by checking out IBM developerWorks' Eclipse project resources.
-
To listen to interesting interviews and discussions for software developers, check out
check out developerWorks podcasts.
-
Stay current with developerWorks' Technical events and webcasts.
-
Watch and learn about IBM and open source technologies and product functions with the
no-cost developerWorks On demand demos.
-
Check out upcoming conferences, trade shows, webcasts, and other Events around the world that are of interest to IBM open source developers.
-
Visit the developerWorks Open source zone for extensive how-to information, tools, and project updates to help you develop with open source technologies and use them with IBM's products.
Get products and technologies
Discuss
-
The Eclipse Platform newsgroups should be your first stop to discuss questions regarding Eclipse. (Selecting this will launch your default Usenet news reader application and open eclipse.platform.)
-
The Eclipse newsgroups has many resources for people interested in using and extending Eclipse.
-
Participate in developerWorks blogs and get involved in the developerWorks community.
About the authors | 
| | Chris Aniszczyk is an Eclipse committer at IBM Lotus who works on OSGi-related development. His primary focus these days is improving Eclipse's Plug-in Development Environment (PDE) and spreading the Eclipse love inside of IBM's Lotus organization. He is an open source enthusiast at heart, specializing in open source evangelism. He evangelizes about Eclipse in his blog, and he's honored to represent the Eclipse committers on the Eclipse Foundation's board of directors. He's always available to discuss open source and Eclipse over a frosty beverage. |
| | | David Gallardo is an independent software consultant and author
specializing in software internationalization, Java Web applications and
database development. He has been a professional software engineer for over
15 years and has experience with many operating systems, programming
languages and network protocols. His recent experience includes leading
database and internationalization development at a business-to-business
e-commerce company, TradeAccess, Inc. Prior to that, he was a senior engineer
in the International Product Development group at Lotus Development Corporation
where he contributed to the development of a cross-platform library providing
Unicode and international language support for Lotus products including Domino. |
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