Wizard API updated!
Tim Boudreau has released a new version of the Swing Wizard library (version 0.997) that fixes the WizardException bug reported in JavaWorld's recent Open Source Java Project profile. The article's examples have been reworked to test out the new, improved WizardException. Thanks, Tim, for this helpful fix!
Open Source Java Projects: The Wizard API

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Reflections on Java, Beans, and relational databases

Here's how to get to your relational database with the new 1.1 APIs

By Sandor Spruit, JavaWorld.com, 09/01/97

A relational database basically consists of a set of interconnected tables, where each table stores one sort of data relevant to the application. An address book database might, for example, have tables for people, addresses, phone numbers, and so on. Each of these entities would be stored in the database as series of strings, integers, and other primitive types. The definition of the database tables would describe how the relevant information on each type of entity is to be stored in a table's columns. You could, for example, have a "person" table with columns meant to contain strings to store "first name" and "last name." Each table should have one or more columns containing a value to uniquely identify each row. These identifiers or "keys" are used to connect the information in different tables. You could, for example, assign a unique "person_number" to each person in the "person" table and use the same numbers in an extra column of the "address" table. You could then link people to addresses by matching values in both "person_number" columns.

Relational database systems have been around since the 1970s, and nowadays they are the predominant way to store large amounts of data. Hence, Java software tools are needed to access the databases built using these systems.

There are, basically, two problems that need to be solved before a relational database can be used from within a Java application. First, you need some basic middleware to establish the connection with the database, send SQL queries to it, and so forth. Second, you would like to manipulate the results just as you do any other piece of information in Java -- as objects. The former already has been solved by Sun and several database vendors; the latter is left for us to work on.

Sun has been cooperating with many software companies to define a large number of APIs for common programming tasks. The API for Java database connectivity (JDBC) was among the first JDK 1.1 APIs to stabilize, and there are numerous implementations of it available from various sources. Some of these are 100 percent pure Java. Others use a mixture of Java and native code to connect to, for example, existing ODBC data sources (see Figure 1). The JavaSoft people have put an extensive overview of available JDBC drivers on their Web site at http://splash.javasoft.com/jdbc/jdbc.drivers.html.

The pros and cons of each of these implementations obviously depend heavily on your particular set-up and environment, and therefore I will not discuss each of them individually. There are just too many drivers from too many different vendors to get all this information into one article. Furthermore, most of the Java files available for downloading on the 'Net contain detailed release notes describing the installation procedures. Therefore, I will assume throughout the rest of this article that you have at least some Java development environment up and running, and that you have successfully installed and tested either a JDBC driver or a driver plus Sun's JDBC/ODBC bridge. In other words: I will assume you are ready to develop some JDBC-based software.

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