TweetFollow Us on Twitter

Building Beans

Volume Number: 13 (1997)
Issue Number: 6
Column Tag: Javatech

Volume Number: 13 (1997)
Issue Number: 6
Column Tag: Javatech

Building Beans

by Will Iverson, Apple Computer, Inc.

Building a better application quicker with JavaBeans

Understanding JavaBeans

Over the last few years, we've heard a lot about component technologies, or software broken up into discrete, mixable sections. From a certain perspective, this includes such a broad umbrella of component technologies as OpenDoc, OLE, ActiveX, VBXs, OCXs, MacOS Extensions (INITs), Photoshop Plug-ins, Netscape Navigator Plug-ins, Control Strip Modules, DCMDs, and even BBEdit Extensions. This is a remarkable list, and includes some of the most interesting and powerful technologies available.

The latest entry to the field is one of particular interest to developers. JavaBeans, in the current incarnation, is a component architecture for development tool plug-ins. JavaSoft has hinted at plans to make JavaBeans spread further than tools -- how this will pan out remains to be seen. Given the recent introduction of JavaBeans, this article will cover what a JavaBean is and provide a brief introduction of how to build a JavaBean.

Most of the information provided in this article is based on the JavaBeans 1.0 specification available from JavaSoft. The reader is advised to frequently check the JavaSoft site at to stay abreast of the latest revisions to the specification.

To take full advantage of JavaBeans requires the use of the JDK 1.1, which on the MacOS means you will need to use MRJ 2.0. By the time this article is printed, a developer release of MRJ 2.0 should be available from

What is a JavaBean?

Taken directly from the specification: "a JavaBean is a reusable software component that can be manipulated visually in a builder tool." As of this writing, the only tool available for the Mac which comes close to implementing the spirit of JavaBeans is Symantec Visual Cafe, and this is the program from which screenshots below are taken.

The high level concept is simple -- there is a modular component architecture for the creation of developer components. Although some mention is made of JavaBeans as a compound document architecture, there is virtually no support for end user manipulation.

Figure 1.

In the builder tools above, you will see three windows. The toolbar is a clumping of the available components, the visual designer is the current visual interface being worked on, and the property list shows the editable values of the selected component.

Figure 2.

Figure 3.

Another critical element of JavaBeans is the capacity to link them together, to support passing events from one JavaBean to another as a way of triggering complex, possibly even cascading interactions. It's worth pointing out here that JavaBeans can be (and often are) not visually presented when the programming is running. A case in point is the example above -- a "timer" JavaBeans is a "visual" representation of a thread which fires at an given interval. The "timer event" is triggered when that interval is hit. When the "timer event" goes off, it tells the progress bar to update itself to the value specified, in this case a hypothetical connection progress status from a connect object's method. The timer isn't visual to the end user, but it can be manipulated through the property sheet by the developer.

You've probably already worked with some sort of visual builder tool -- ResEdit and the Metrowerks PowerPlant Constructor are examples. There are two fundamental problems with most of the mainstream tools that make them less than ideal.

  1. You can't add anything to the tool palettes.
  2. You have to switch between an environment for doing your visual design and writing your code (often having to close the visual design document before being able to run from your coding environment.
  3. The visual form builder typically has no good way to associate code with the visual elements -- typically strings or ID numbers are used, which can be a headache to track, especially for larger projects.
  4. Visual elements are limited to human interface, such as buttons, dialogs and menubars.

JavaBeans is designed to solve these problems.

Why is Visual Café Not JavaBeans?

When the Visual Cafe project was begun, JavaBeans didn't exist. Symantec worked with JavaSoft in designing the specification, but the bulk of the JavaBeans functionality, such as support for the new event model and introspection, (described later in this article) weren't available until the release of JDK 1.1. In order to "hack" around this limitation, Symantec developed a series of "descriptor" files. These '.desc' files are simple text files and can be found in the "Components" folder next to Visual Cafe. If you're interested, you can open these files up and take a look at how they were built. Symantec Visual Cafe 1.0.1 includes a pdf file describing the format of these desc files.

For a JavaBean developer, as long as you stick to the JavaBean "design patterns," also described below, you should be fine in the long term. If you'd like to make your JavaBean accessible to Visual Cafe 1.0, you can take a stab at trying to figure out the format to the desc files, but understand that these files are specific to Visual Cafe. The good news is that if you've done your job with the design patterns properly, you won't care - it'll just make your life easier.

How do JavaBeans Work?

Now that you've been given a taste of how a JavaBean is used, let's take a look at how a JavaBean is designed.

A JavaBean typically encounters three "classes" of people, the developer of the JavaBean (the "programmer"), the user of the JavaBean (the visual builder user), and the end user (or "client"). Note that the programmer and the visual builder may be the same person, but the assumption is that they are not.

  1. A programmer decides to create a JavaBean, either to share with others, to sell, or simply to make her code easier to reuse.
  2. The JavaBean is created using the JavaBeans design patterns.
  3. The JavaBean is packaged as a JAR file.
  4. The visual builder user adds the JavaBean to the her development environment's library with the "Add Component" command or similar action.
  5. The visual builder user drags the JavaBean from the component library to the project.
  6. The visual builder user sets the JavaBean properties and events with the visual builder or makes use of the JavaBean directly from traditional code.
  7. The visual builder user builds the application or applet and gives it to the client.
  8. The client uses the application, either as an applet, an application, or even as a Marimba channel.

Note that the "hard" work of developing the JavaBean by the programmer can be leveraged by dozens or thousands of visual builder users.

What Versions Of the MRJ Support Beans?

The initial release of the JDK 1.0 last year was less than ideal, and plagued by more than a few bugs. JavaSoft quickly realized that Java needed some quick patchup work, and came out with the JDK 1.02, essentially a bugfix version of the initial JDK specification. This is the version of the JDK which is incorporated into Netscape Navigator and is the foundation for the MacOS Runtime For Java (MRJ) 1.0. As anyone who has played with Java extensively realizes, JavaSoft didn't fix all of the bugs, and that's what takes so long for an implementation of the JDK to go final.

The MRJ 1.5, which may be available as a final release by the time this article is printed, is an implementation of the JDK 1.02 specification with the additional of the performance technology known as a JITc. Simply put, a JITc remembers that it has converted a section of bytecode to native code, and then caches that code. Typically, this results in an across the board CaffeineMark improvement of x10, with specific benchmarks ranging from no effect to over x20.

The MRJ 2.0, which will be available as a developer release this summer, is an implementation of the JDK 1.1, the new release from JavaSoft featuring a host of new features, many of which are required for Beans support, including Introspection, Reflection, RMI, Serialization, Internationalization, and other technologies.

The nice thing about the MRJ is that it isolates the Java VM from a specific application. You might want to install one version for customers, and use a different version for development purposes. That way, you can make your own decisions about your mix of bleeding edge and final release software, important when trying to stay on top of the latest technologies.

What are Design Patterns?

Design patterns are standardized ways of writing methods and interfaces. The simple example is of the property "Foo" which is set and retrieved with the functions "getFoo" and "setFoo." Design patterns may be used to specify events, public methods, and properties.

This is useful both for self-documentation as well as automatic code generation. When a property is set in a builder tool, it generates the code based on these patterns. For example, if the user sets the value of "Foo" to "Bar" then the builder would generate the code setFoo("Bar"); automatically (or use Serialization, but that's another topic).

Alternatively, a developer may provide all of this information through a "BeanInfo" function. Certain builder tools may be able to extract additional information through this mechanism, such as the icon to be drawn to represent a JavaBean or localized versions of the properties and events. Developers interested in the development of serious JavaBeans should review the documentation available from JavaSoft.

Note that successful design patterns require a few basic rules of thumb. First, different tools may wish to use the set and get methods in any order. Typically, this is not a problem -- you can call something a "blue, translucent rectangle" or a "translucent, blue rectangle" without changing the results, but certain designs will imply changes.

Design patterns exist for several standard concepts, including those listed below:

Simple properties are the basic "get" and "set" methods. To define a simple property, include methods of the form

public <PropertyType> get<PropertyName>()
public void set<PropertyName>(<PropertyType> x)

For example, you could define your own Rectangle class, and include the following methods:

public Color getColor()
public void setColor(Color x)

Note that the builder tool may recognize certain standard PropertyNames and provide certain standard pickers. For example, Visual Cafe brings up the Apple Color Picker when a property has the PropertyType Color.

A property may be formatted as public boolean is <PropertyName>(); format instead of a public <PropertyType> get <PropertyName>(); for better readability for English readers.

Indexed properties are also supported with the standard format of

public <PropertyType> get<PropertyName>(int i)
public void set<PropertyName>(int i, <PropertyType> x)

The New Event Model

Events are also defined by Design Patterns. The model for handling events has changed significantly in the JDK 1.1 from the 1.02 implementation. This is probably the area of your code which will require the most tweaking for general ports to JDK 1.1, regardless of whether or not you pay any attention to JavaBeans. While the JDK 1.1 supports the 1.02 event model, it does not support intermixing the 1.1 and the 1.02 models. Before we can talk about events and JavaBeans, we have to briefly dive into the new JDK 1.1 events.

JDK 1.1 introduces a new event model based on the concept of listeners. The idea is simple -- rather than poll for events repeatedly, your code registers itself as being interested in specific types of events. In other words, instead of asking every few seconds "what happened," your code simply says "tell me when this happens." This dramatically cuts down on the overhead for your code, especially in complex situations. For example, consider the mouse moved event -- with a polling model (or any event model without a registration mechanism, such as the JDK 1.02 AWT), this results in a fantastic number of events being generated (and much wasted processor time) -- even if no one is listening!

First, write the code which will handle the events. This class may implement one of the following:


These are interfaces and therefore you will have to actually implement all of the methods for the class. This can be tedious, but you can optionally use one of the "adaptor" classes which provide empty methods for all of the corresponding Listener's methods. This allows you to use extends instead of implements, which may save you some code. You may have noticed that there are fewer adaptors than listeners -- some listeners, such as ActionListener, have a single method and an adaptor would serve no purpose:


Your Listener or Adapter will receive an event when triggered. These events may be one of the following standard types:


The new event model appears more complex than it actually is. Those of you familiar with many of the frameworks or message-based event models will have a leg up on those who are used to the standard MacOS event loop. Just remember, a Listener is the code that will be triggered by the event (the code that says "I want keystrokes"), and an Event object is a bit of state referring to a specific occurrence of the event (a notification the user pressed 'a'). For our purposes, an adapter is a programmer's aid for implementing a Listener.

Where's my IDL?

Those of you familiar with other mechanisms such as SOM may have noticed the lack of any sort of interface definition files. Simply writing public boolean isAsleep(); is certainly a lot easier than writing SOM idl files, or trying to write COM interfaces by hand. Compiler vendors have made stabs at trying to solve the complexities of SOM and COM with varying degrees of success. Why is this?

C++ libraries are statically compiled code - code which loses most of the type information as it is built. Everything is done as offsets from pointers, with no runtime enforced type checking. For example, any arbitrary pointer can be set and written to - there is no verification that the target of a write is an appropriate location. This is the source of a lot of crashes and memory corruption.

In the original design of Java, all of the type data was kept around in the bytecode. This was originally done to make sure that if an inappropriate cast was made, the runtime would catch the error and throw an exception. C++ added a similar concept called RTTI (runtime type identification) recently, but it doesn't include a lot of the safety checking. As a side effect, it turns out that all of this type information is very handy for parsing the structure of a chunk of code, and made the design of JavaBeans a lot cleaner and more elegant than previous technologies.

Making Your Own Events

The JDK draws a distinction between "low-level" events, such as a mouse down or a mouse moved, and a "semantic" event, such as an action event which is generated by a button press. It is possible for JavaBeans to define their own semantic, higher level events.

Create your own Listener class by implementing an EventListener, and your new event types by implementing an EventObject. Then use the following methods to register your interest in the events, and use the methods above to handle the events:

public void add<EventListenerType>(<EventListenerType> a)
public void remove<EventListenerType(<EventListenerType> a)

It is worth spending some time to carefully plan how you will use these new events, and by adhering to design patterns such as

void <eventOccurenceMethodName>
      (<EventStateObjectType> evt);

You can allow visual builder tools to take advantage of your new event type. An example of this would be

public class ControlEvent extends java.util.EventObject {
	// this event might have an additional method,
	// such as a getValue() if it were a scrollbar 

interface ControlListener extends java.util.EventListener {
	void controlFired(ControlEvent ce);
	void controlDeactivated(ControlEvent ce);
	// these are the methods to be implemented
	// by code interested in the ControlEvent

Dive into the JDK 1.1 API level documentation for the new event APIs. As of this writing, you'll have to get your hands dirty by playing with the html documentation directly from JavaSoft.

Final Notes

All public methods may theoretically be exposed to the builder tool. Properties and events which make use of the guidelines above can typically take advantage of the standard tools available to the builder tool (such as standard popups for selecting booleans in the Properties palette, automatically generated Font menus, color pickers, etc.). A suite of well designed components allows you to tie an awful lot of functionality together extremely rapidly; by creating your own you make it much easier for others to leverage your work. There was an awful lot of material of interest to JavaBeans developers we didn't cover here, including Serialization (persistent objects), RMI, and more. Despite the emphasis on visual builder tools, JavaBeans are completely usable directly from a "traditional" environment with handwritten source code.

This article covered the initial concepts of JavaBeans, including the notions of properties and events, and it covered the structure behind how basic JavaBeans are built. Hopefully this is enough for you to get started, and enough for you to understand a bit more about what's going on "under the hood" with JavaBeans. Start off by playing around with Visual Cafe or another JavaBeans visual tool, and once you get a feel for how it works, try making your own JavaBean by taking advantage of the design patterns and property definitions. Once you've gotten a feel for how this works, try playing around with the new event model, defining your own events and understanding how the firing chain of an event works.

Good luck, and I hope JavaBeans helps make writing (and using) code that much easier.


Community Search:
MacTech Search:

Software Updates via MacUpdate

Microsoft Office 2016 16.11 - Popular pr...
Microsoft Office 2016 - Unmistakably Office, designed for Mac. The new versions of Word, Excel, PowerPoint, Outlook, and OneNote provide the best of both worlds for Mac users - the familiar Office... Read more
Adobe Photoshop CC 2018 19.1.2 - Profess...
Photoshop CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Photoshop customer). Adobe Photoshop CC 2018, the industry standard... Read more
Adobe Dreamweaver CC 2018 -...
Dreamweaver CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Dreamweaver customer). Adobe Dreamweaver CC 2018 allows you to... Read more
Adobe Flash Player - Plug-in...
Adobe Flash Player is a cross-platform, browser-based application runtime that provides uncompromised viewing of expressive applications, content, and videos across browsers and operating systems.... Read more
Drive Genius 5.2.0 - $79.00
Drive Genius features a comprehensive Malware Scan. Automate your malware protection. Protect your investment from any threat. The Malware Scan is part of the automated DrivePulse utility. DrivePulse... Read more
MegaSeg 6.0.6 - Professional DJ and radi...
MegaSeg is a complete solution for pro audio/video DJ mixing, radio automation, and music scheduling with rock-solid performance and an easy-to-use design. Mix with visual waveforms and Magic... Read more
ffWorks 1.0.7 - Convert multimedia files...
ffWorks (was iFFmpeg), focused on simplicity, brings a fresh approach to the use of FFmpeg, allowing you to create ultra-high-quality movies without the need to write a single line of code on the... Read more
Dash 4.1.5 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
Evernote 7.0.3 - Create searchable notes...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
jAlbum Pro 15.3 - Organize your digital...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. You can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly... Read more

Latest Forum Discussions

See All

All the best games on sale for iPhone an...
It might not have been the greatest week for new releases on the App Store, but don't let that get you down, because there are some truly incredible games on sale for iPhone and iPad right now. Seriously, you could buy anything on this list and I... | Read more »
Everything You Need to Know About The Fo...
In just over a week, Epic Games has made a flurry of announcements. First, they revealed that Fortnite—their ultra-popular PUBG competitor—is coming to mobile. This was followed by brief sign-up period for interested beta testers before sending out... | Read more »
The best games that came out for iPhone...
It's not been the best week for games on the App Store. There are a few decent ones here and there, but nothing that's really going to make you throw down what you're doing and run to the nearest WiFi hotspot in order to download it. That's not to... | Read more »
Death Coming (Games)
Death Coming Device: iOS Universal Category: Games Price: $1.99, Version: (iTunes) Description: --- Background Story ---You Died. Pure and simple, but death was not the end. You have become an agent of Death: a... | Read more »
Hints, tips, and tricks for Empires and...
Empires and Puzzles is a slick match-stuff RPG that mixes in a bunch of city-building aspects to keep things fresh. And it's currently the Game of the Day over on the App Store. So, if you're picking it up for the first time today, we thought it'd... | Read more »
What You Need to Know About Sam Barlow’s...
Sam Barlow’s follow up to Her Story is #WarGames, an interactive video series that reimagines the 1983 film WarGames in a more present day context. It’s not exactly a game, but it’s definitely still interesting. Here are the top things you should... | Read more »
Pixel Plex Guide - How to Build Better T...
Pixel Plex is the latest city builder that has come to the App Store, and it takes a pretty different tact than the ones that came before it. Instead of being in charge of your own city by yourself, you have to work together with other players to... | Read more »
Fortnite Will Be Better Than PUBG on Mob...
Before last week, if you asked me which game I prefer between Fortnite Battle Royale and PlayerUnknown’s Battlegrounds (PUBG), I’d choose the latter just about 100% of the time. Now that we know that both games are primed to hit our mobile screens... | Read more »
Siege of Dragonspear (Games)
Siege of Dragonspear 2.5.12 Device: iOS Universal Category: Games Price: $9.99, Version: 2.5.12 (iTunes) Description: Experience the Siege of Dragonspear, an epic Baldur’s Gate tale, filled with with intrigue, magic, and monsters.... | Read more »
7 Wonders Guide - Should You Buy The Lea...
The fantastic mobile version of 7 Wonders just got updated with an expansion that adds Leaders to the game. This new content adds a whole layer of depth to the game, but before you spend $1.99 to buy it blindly, check out this breakdown of exactly... | Read more »

Price Scanner via

B&H drops prices on 15″ MacBook Pros up t...
B&H Photo has dropped prices on new 2017 15″ MacBook Pros, now up to $300 off MSRP and matching Adorama’s price drop yesterday. Shipping is free, and B&H charges sales tax for NY & NJ... Read more
Apple restocks Certified Refurbished 2017 13″...
Apple has restocked Certified Refurbished 2017 13″ 2.3GHz MacBook Pros for $200-$230 off MSRP. A standard Apple one-year warranty is included with each MacBook, models receive new outer cases, and... Read more
13″ Space Gray Touch Bar MacBook Pros on sale...
Adorama has new 2017 13″ Space Gray Touch Bar MacBook Pros on sale for $150 off MSRP. Shipping is free, and Adorama charges sales tax in NY & NJ only: – 13″ 3.1GHz/256GB Space Gray MacBook Pro (... Read more
Best deal of the year on 15″ Apple MacBook Pr...
Adorama has New 2017 15″ MacBook Pros on sale for up to $300 off MSRP. Shipping is free, and Adorama charges sales tax in NJ and NY only: – 15″ 2.8GHz Touch Bar MacBook Pro Space Gray (MPTR2LL/A): $... Read more
Save $100-$150+ on 13″ Touch Bar MacBook Pros...
B&H Photo has 13″ Touch Bar MacBook Pros on sale for $100-$150 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 13″ 3.1GHz/256GB Space Gray MacBook Pro... Read more
Current deals on 27″ Apple iMacs, models up t...
B&H Photo has 27″ iMacs on sale for up to $150 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 27″ 3.8GHz iMac (MNED2LL/A): $2149 $150 off MSRP – 27″ 3... Read more
Thursday Deal: 13″ 2.3GHz MacBook Pro for $11...
B&H Photo has the 13″ 2.3GHz/128GB Space Gray MacBook Pro on sale for $100 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 13-inch 2.3GHz/128GB Space... Read more
How to save $100-$190 on 10″ & 12″ iPad P...
Apple is now offering Certified Refurbished 2017 10″ and 12″ iPad Pros for $100-$190 off MSRP, depending on the model. An Apple one-year warranty is included with each model, and shipping is free: –... Read more
Silver 12″ 1.3GHz MacBook on sale at B&H...
B&H Photo has the 2017 12″ 1.3GHz Silver MacBook on sale for $1399.99 including free shipping plus sales tax for NY & NJ residents only. Their price is $200 off MSRP, and it’s the lowest... Read more
Amazon offers 21″ Apple iMacs for up to $150...
Amazon 21″ iMacs on sale today for $50-$150 off MSRP, depending on the model. Shipping is free: – 21″ 3.4GHz 4K iMac (MNE02LL/A): $1349.99 $150 off MSRP – 21″ 3.0GHz iMac (MNDY2LL/A): $1199 $100 off... Read more

Jobs Board

Data Scientist, *Apple* Ecosystem (AMP Anal...
# Data Scientist, Apple Ecosystem (AMP Analytics) Job Number: 113428728 Santa Clara Valley, California, United States Posted: 24-Jan-2018 Weekly Hours: 40.00 **Job Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 113523441 Orange, CA, California, United States Posted: 21-Feb-2018 Weekly Hours: 40.00 **Job Summary** Are you passionate Read more
*Apple* Professional Learning Specialist - A...
# Apple Professional Learning Specialist Job Number: 113456892 Englewood, NJ, New Jersey, United States Posted: 02-Feb-2018 Weekly Hours: 40.00 **Job Summary** The Read more
*Apple* Retail Online, Senior Financial Anal...
# Apple Retail Online, Senior Financial Analyst Job Number: 57228835 Santa Clara Valley, California, United States Posted: 12-Feb-2018 Weekly Hours: 40.00 **Job Read more
Site Reliability Engineer, *Apple* Pay - Ap...
# Site Reliability Engineer, Apple Pay Job Number: 113356036 Santa Clara Valley, California, United States Posted: 12-Jan-2018 Weekly Hours: 40.00 **Job Summary** Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.