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BROKAT is a German software house that develops and implements  object-oriented transaction solutions for financial service companies. 
The company's flagship product, Twister 2.0, is billed as the BROKAT  middleware solution. It uses CORBA and supports nearly all server platforms.  Twister applications "offer customers the shortest time to market  and optimum levels of investment protection," the company declares.

In this guest article, BROKAT engineer Dietrich Pfeifle shows how  the creators of Twister 2.0 migrated from AWT to Swing, and explains why.

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When we received the first release of JFC (also called Swing) in February 1998, we and other developers working  in the Java^TM programming language asked ourselves:  What are pros and cons of this new way of life -- this Swing?

This article briefly outlines how we answered that question. It also  tells how -- and why -- a modern company like BROKAT decided to migrate  from AWT to Swing.

As a special bonus, it presents several  code snippets and a small demo applet to show how our company uses Swing.

 

Using Swing for client GUIs

When this article was written, the latest figures showed that 1,439 banks  were using secure banking solutions offered by BROKAT. As the following  screen shot shows, Twister products use applets written in the Java programming  language to create good-looking, easy-to-use graphical interfaces for  clients.

 

The Java language helps us develop client applications in a very short  time, and ensures that they are platform-independent and globally and  quickly updatable.

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Swing and mobile banking

One of our Twister applications, X·SMS Banking, permits financial  applications to be called up by GSM mobile phones using the Short Message  Service (SMS). With X·SMS Banking, clients can perform operations  such as checking their accounts or performing transfer orders by mobile  phone. Also, mobile phones can be used in such cross-channel applications  as devices for providing digital signatures for PC-based Internet transactions.  BROKAT demonstrated this new solution at the German fair CEBIT '98 with  great success.

This diagram shows how X·SMS Banking works:

 

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Transactions by the numbers

The operation shown in the diagram works as follows:

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Repudiating transactions

 If an online customer repudiates a transaction at a later  time -- even weeks later -- he can simply call his bank. Then it's up  to the bank to verify the validity of the specified transaction. To do  this, it is necessary to check the transaction again.

But that's easy. The transaction is exported from database, and the signature  is generated again. the the generated signature is compared with the stored  one, and both the timestamp and the validity of the certificate are also  tested.

Because all these operations are necessary, we need an easy-to-understand  GUI that offers quick access to a very large amount of information. We  decided to use JFC -- and it was a good decision. That's because JFC works well in a typical client-server-infrastructure.  In such an infrastructure, all decisions are up to the server, and so  is database management, but the client must be able to handle and display  a very large amount of data.

Benefits of using Swing

We were glad to discover that the Swing API has nearly the same structure  as the AWT. For example, although a button is called JButton instead of  Button in Swing, it retains the standard methods of AWT's Button class.  But it also has some cool extra features, such as letting one add a picture.  In the old days, everyone created their own implementations of such things  -- so we were able to combine the old with the new every time we went  back to the drawing board.

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Rapid-fire programming

Every applet programmer knows the fundamentals of AWT programming, and  some have bemoaned its lack of a comfortable and flexible table representation.

Times have changed. Our graphical user interface was implemented in an  extremely short time -- in about 2 weeks -- because it has become easy  to use tables, trees, image components, pictures on buttons, and the like.

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JTable: a big double-buffered picture

All old AWT components kept their data in own variables, arrays, and  the like. But Swing offers a whole new way of life. In Swing, you can  define classes that can handle data in the background, sorting it as the  visualizer itself just visualizes data.

With Swing tables, you can work with ranges of records; for you can give  a JTable object such instructions as: "Shows me customer 103 up to  181."

 

Also, you can easily scroll through hundreds of lines. No flickering.  No crashing.

Another important feature: If your data keeping class is updated, because  a new request has been set up, for example -- your table is updated automatically  !

In short, Swing enabled us to implement a generic solution to display  all possible data in one and only result window. Such code is often reusable  and could be very flexible.

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We want small applets!

If you you write an applet that turns out to be 400K long, your users  have to drink more than one cup of coffee while your applet is loading.  So programmers are always trying to optimize applet code.

Swing has helped us provide applets with good functionality and small  size (40 kBytes are so). Why? Because all the JFC classes are permanently  stored in the user's class path. So they don't have to be downloaded every  an applet is used. This is a welcome relief, in contrast to self-implemented  tables, picture-buttons, trees, and so on.

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We want good window-handling!

With the help of Swing, we have found that it's easy to emulate a windowing  system such as the Windows MDI (multiple document interface) design. Now  that developers can develop custom windowing systems with Swing, imagine what kinds of applets might be coming in the future! To see one possible example, follow this link.

I implemented several GUI's with the Java 1.0.2 release and had many  problems with Dialogs and Frames because of the difficulty in emulating  windowing systems. When a windowing system is not provided by the API  one is working with, it costs application developers lots of time and  money. The only thing one can do in such a situation is write one's own  code -- which, more often than not, turns out to be non-portable. Swing  solves that problem by providing an interface that makes it easy to create  standard dialogs, such as error-message dialogs, warning dialogs, "Yes/No"dialogs,  and so on.

The following pictures show how Swing was used to create a simple standard  dialog in three different look-and-feel implementations. You can view  or download a code sample by following this link.

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I almost  forgot to mention the coolest feature of JFC: Its support of a platform-independent  pluggable look and feel. You can rest assured that all your colleagues  will look surprised the first time you simply chose "Motif"  from a Windows a menu and then watch all your components change to look  like Motif. And if you choose "Java L&F," make sure you've  provided enough seats!

To see an example, follow this link.  Also, the three thumbnail screen shots that appear below blow up to full  size when you click them. They show the same application in three different  L&F implementations.

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Overview of sample code and demos

To see Swing in action, check out the following code snippets and run  the small test applet I've provided. To start the applet, you must have Swing installed  in your browser's class path. So download the JFC package from java.sun.com and then install the snippets locally. (If your browser and your computer  system aren't yet set up to run Swing applications, you can fix that by  following the instructions provided in the articles in this issue titled  "Plug-in Power" and "Make  Your Browser Swing.")

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Conclusion (but not the end) . . .

I hope this article has helped you get into the spirit of Swing. I've  watched it infect several colleagues of mine when they discovered the  Java Foundation (Swing) Classes. All of them were programmers who worked  in the Java language, and all were fascinated from the great features  that Swing offers.

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AWT, JFC: If you aren't familiar with JFC or AWT, we suggest  that you read the "Introducing Swing" article in this issue.

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In this section, The Swing Connection publishes articles that are written by third-party
developers and may contain code, statements, inferences, and programming techniques that are not necessarily endorsed by Sun Microsystems, Inc., or by The Swing Connection.