Java(TM) Boutique - Mapping Java Objects to a Database with Castor-JDO

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Mapping Java Objects to a Database with Castor-JDO:

Installation of MySQL

Castor supports all the well-known high-end databases like Oracle, DB2, MS SQL Server, but also Open Source databases like MySQL and Postgres. Here's the complete list of supported database systems. For all the examples in this article I've used MySQL, and for those of you who don't already have a database running on your computer I'll show you how to get one.

You're always told that software is easy to install, right? This time it's true! MySQL is really simple to install and use. To use MySQL we need three software components:

the MySQL server
a GUI client to administer the MySQL server
a Java JDBC driver

You'll find them all on the MySQL download page: http://www.mysql.com/downloads/index.html.

The MySQL server: The production release is currently 3.23, but there is a "gamma" release called 4.0 which is recommended for new development, so let's pick that one. I used version 4.0.10 for this article. It's quite a bit to download, more than 20M for my Windows98 computer. On Windows you unzip the files, run the setup.exe, install in c:\mysql, and you're ready to go.

There's a very comprehensive manual in the download, but why not start the server right away? Open a command prompt, go to the mysql\bin directory and type "mysqld", and the server is running. Verify this by typing "mysql" and you're in the server administrator. Now type "show databases;"--remember the semicolon! This will list the two databases--mysql and test--which come with the download. Enter "use test", and then create a new table called "media" in the "test" database:

create table media (id int primary key, type char(10) not null);

Enter "exit" to leave the administrator.

The GUI client: Several clients exist. On the MySQL download page you'll find a link to "MySQL Control Center", which is a client that'll give you all the essential features you'd need to administer MySQL. Installation is straightforward. I used version 0.8.10 when preparing this article.

You should be able to see the new "media" table in the "test" database.

The JDBC driver: Also on the download page you'll find "MySQL Connector/J", which is the official JDBC driver. Unzip the file you've downloaded and place the jar-file (there's only one) in your classpath. To see if your setup is correct try to compile and run this simple program that'll show the names of all tables in the "test" data base:

package hansen.playground;

import java.sql.*;

public class TestMySQL {
  public static void main(String[] args) {
    Connection connection = null;
    try {
      // Load the MySQL JDBC driver
      String driverName = "org.gjt.mm.mysql.Driver"; 
      Class.forName(driverName);
      
      // Create a connection to the "test" database
      String serverName = "localhost";
      String mydatabase = "test";
      String url = "jdbc:mysql://" + serverName +  "/" + mydatabase;
      String username = "root"; // default
      String password = ""; // default
      connection = DriverManager.getConnection(url, username, password);
      
      // Get the database metadata
      DatabaseMetaData dbmd = connection.getMetaData();
  
      // Specify the type of object; in this case we want tables
      String[] types = {"TABLE"};
      ResultSet resultSet = dbmd.getTables(null, null, "%", types);
  
      // Get the table names
      while (resultSet.next()) {
        // Get the table name
        String tableName = resultSet.getString(3);
        System.out.println("Table: " + tableName); 
      }
    } catch (ClassNotFoundException e) {
      e.printStackTrace();
    } catch (SQLException e) {
      e.printStackTrace();
    }
  }
}

- Listing 1: Testprogram for MySQL -

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