If your system has an up-and-running Sun JDK 1.1 or higher, it should meet these requirements.

Installation from the CD-ROM was basic and took only a few minutes. After installation is complete, it is necessary to perform a few steps:

Using TopLink
I found installation and configuration of TopLink to be smooth and uncomplicated. Now that the application is up and running, let's look at what it can do. I'll use the example supplied with the application to demonstrate some of the steps necessary to create a simple database application.

The sample included with the software is an employee management database. It keeps track of information for all full-time and contract employees, including addresses and phone numbers. The object model being built consists of three classes:
1. The Employee class represents all employees, both full time and contracted. It includes all personal information, including references to home addresses and phone numbers.
2. The Address class represents home address. This includes country, street, city and zip code.
3. The Phone number class contains, as you may have guessed, the phone number including area code.

Each of the above classes contains cross-references to the others. The relational database stores all of this information in three tables, much in the same fashion that I've built the object model. It is important to point out here that it's not necessary to structure the object model after the table structure of the relational database. The object model can be based on application requirements rather than the database structure. This is a great feature, as the developer is not bound to the relational database structure.

TopLink communicates with a relational database via a Database Session. This Java class keeps track of the following information:

Logging into the Database
In order to login to a database, it is first necessary to create a JDBCLogin instance. This holds the login parameters including the database name and type. This class is then passed to the DatabaseSession, which allows the login to occur. Here's a small fragment of the code that allows the creation of a login instance:

Import TOPLink.Public.PublicInterface*;
Import TOPLink.Public.Exceptions*;
Project project = TOPLink.Public.
PublicInterface.Project.read(
“C:\\TOPLink\\BuilderDemos\\Emloyee.
project”)

Now that the database is logged into, it's time to discuss the initialization of the descriptors. This is done by the following steps:
1. Create a Project using the TopLink Builder tool. This is a stand-alone application used to create and manage the descriptors and mappings. It's GUI interfaced and looks like your typical drop-menu driven application. It obtains data from the database and stores it in Table files. Class Definition files generated from the persistent Java classes are supplied, and the Builder is then used to map the table columns to class attributes. The Builder then writes Descriptor files to these mappings. These are used by the Java application to access the database.
2. If required, modify your persistent Java classes. It is required that all persistent classes have a public default constructor which has no arguments. If any of the class attributes are declared private, it is necessary to create accessor methods to allow them to be written to the database.
3. Create Class Definition Files for each of the persistent Java classes. Each of the Java classes in the project must have a descriptor. Opening the Builder and selecting "Add/Update" classes from the Descriptor menu can create these.
4. Use the Builder's Database Login screen to connect to the database. This is done by selecting "Login To The Database" from the Builder menu. A dialogue box will drop open, allowing database connection information to be entered.
5. Import table information from the database to the project. This is also done through the builder. All that's involved here is selecting the "Add Existing" from the Tables menu.

All in all, it really hasn't been too difficult up to this point. There has been a little filling in the blanks of code, and then compiling to run, but most of the major jobs were done by clicking on menus. That's pretty amazing, when you consider just how potent an application this is. This fraction of an example only begins to scrape the surface of just how many uses there are for this powerful builder.

It is also possible to develop three-tier applications using TopLink. It supports the following databases (and many others through JDBC drivers):

Mainframe connectivity is also available for legacy data.

TopLink is one of the more powerful database tools I've seen. It offers flexibility and relative user-friendliness for this type of application. For those of you looking for a powerful tool to develop Java applications by using relational databases, or for someone who wants a good tool to develop a three-tier environment, it is definitely a must see.

I remember when I first discovered Java. At first I though it was this neat little scripting language that jazzed up Web pages. I almost immediately discovered that I had underestimated its power. I watched that language, in a relatively short period of time, become a major competitor of C, the age-old deity of programming languages. Now, it seems Java is invading the database management and development platforms as well. Will Java take over these traditional applications, and become the dominant development environment of the next century? That remains to be seen, but applications like TopLink provide a good clue as to what just might happen.