The JavaOne conference saw the announcement of Java Beans, an exciting new component architecture for building modular software systems based on Java^TM. JDC  talked to Graham Hamilton, chief architect of the Java Beans architecture, and the Java Beans API. Graham has been with Sun for seven years, and has contributed to a range of projects, including the Spring distributed operating system, JavaOS, Java IDL, JDBC, and Java Beans.

"I want to emphasize that our goal is not to build end products, or tools," says Hamilton, "but to build the best possible supporting architecture for building Java components. We're not doing this on our own in a vacuum. We're collaborating with prominent tool vendors and developers including Borland, Symantec, IBM, Lotus, Netscape, Rogue Wave, and Justsystem--the largest independent software vendor in Japan. Justsystem is pretty big; they've been called the 'Microsoft' of Japan."

Hamilton says IBM is very active in developing what he calls a "bridge component" for OpenDoc. Other tool builders at IBM are building bridges to make Java Beans work with VisualAge. Borland, Symantec and Lotus are working hard to take advantage of Java Beans technology. JavaSoft itself has built bridge technology to make a Java Bean component completely indistinguishable from an OCX (Visual Basic Control).

Java Beans as Persistent Objects

"We're also working closely with various engineers in other parts of JavaSoft," says Hamilton. "For example, we're using object serialization stuff from Roger Riggs and the East Coast JavaSoft team. This gives us a very powerful form of persistence that makes it possible to save the state of components and to transmit complex components across networks." Support for object serialization brings new meaning to the idea of a reusable component, and will change the way developers distribute and market software.

The distinguishing feature of Java Beans as reusable components is that they interoperate across all  platforms supported by Java. We've seen reusable components before, but they all have been restricted to a single platform. Since the Java^TM Virtual Machine¹ runs on a variety of platforms, a Java component, affectionately called a 'bean' can be used on any platform supporting the Abstract Window Toolkit (awt). A bridge technology, which Hamilton refers to as a "universal adapter" allows a Java Bean component to behave exactly like an OCX that will interoperate with Visual Basic, Delphi, and other applications that support OLE/COM automation.

"With a Java Bean bridge, you can call Java from Visual Basic," says Hamilton, "or you can call from Java into Excel or Word. The technology is very powerful. We've concentrated on providing, through our APIs, a solid interface that will give developers access to just about any events, or properties they are likely to need. In short order, I'm expecting to see some really great products--GUI window builders, development environments, browsers, custom component editors, and debuggers--coming from third party collaborators based on Java Beans."

Keep it Sweet and Simple

Hamilton wants to make it as easy as possible for developers to evaluate Java Beans so that they can assess the feasibility of using Java Bean components in critical projects. "I want people to be able to look at this technology, and within two days, make a decision that it is going to work for them. The entry cost has to be easy, and the learning curve shallow. You shouldn't have to go off and read a 1000-page manual, like Inside OLE  before you can write a moderate component, or make judgements about feasibility and scalability of embedded components to large projects."

To Build or Buy--That's the Question.

Hamilton's notion of how Java Beans will be used by developers is similar to what has taken place with component development for Visual Basic and Delphi. The Java Bean API is important for the success of both groups--component producers and component consumers--but each has a very different need.

We think that we'll see developers using Java Beans fall into two groups. You'll have very expert-level programmers who build the beans or components. Then you'll have bean consumers, people who are experts in their application domain, but who don't want to know the internals of the Java Beans API. They'll take prepackaged beans and use them to build up complex compound components for reuse in various projects throughout the enterprise, and within MIS departments at the corporate and ISV levels.

Using Java Beans

The Java component API adds a dynamic capability to portable Java applets and applications. A button or icon in one document, for instance, can control functions in another document. For example, a button component in one document could trigger a bar chart to be drawn in another document; a live data feed in one document could be represented as a chart in another document.

The Java component API enables powerful integration of component objects into applications in multiple formats and architectures, including HTML, COM, OpenDoc, and LiveConnect. Java Beans components, which will include ordinary Java applets, can also be embedded into existing "containers" such as Netscape Navigator, Microsoft Internet Explorer, Microsoft Word and Excel, Microsoft Visual Basic, and others.

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¹ As used on this web site, the terms "Java virtual machine" or "JVM" mean a virtual machine for the Java platform.