DatabaseConnection.java

public class DatabaseConnection {
    private final static Logger logger = LoggerFactory.getLogger(DatabaseConnection.class);
    private static DatabaseConnection instance;

    private Jdbi dbConnection; // wraps a JDBC DataSource, it is the main configuration for the database.

    private final String dbUrl; // the JDBC URL that is needed to create a connection.
    private final String dbUsername; // the database username needed to create a connection.
    private final String dbPassword; // the database password needed to create a connection.

    /**
     * Creates a DatabaseConnection object with a null connection to the database until obj.connect() is implicitly
     * called. The JDBC URL, database username, and database password will be pulled from the database.properties file
     * at the time of creation, however.
     */
    private DatabaseConnection() {
        this.dbUrl = DatabaseConfig.getInstance().getString("db.jdbc.url");
        this.dbUsername = DatabaseConfig.getInstance().getString("db.uid");
        this.dbPassword = DatabaseConfig.getInstance().getString("db.pwd");
    }

    /**
     * Establishes an entry-point to the database by creating a new Jdbi instance, which wraps a JDBC DataSource and
     * serves as the main configuration point for the database session.
     */
    public void connect() {
        if (this.dbUrl == null || this.dbUrl.isEmpty()) {
            throw new RuntimeException("Invalid dbUrl, check that 'db.jdbc.url' in 'database.properties' is valid.");
        }

        loadJdbcDriver(); // Loads the necessary JDBC connector for establishing database connections.

        logger.info("Connecting to " + getDatabaseName() + " at " + getDatabaseHost() + ":" +
                getPortNumber() + " for user '" + this.dbUsername + "'");

        // Creates the database session connection.
        this.dbConnection = Jdbi.create(this.dbUrl, this.dbUsername, this.dbPassword);

        // Loads the Jdbi Plugin needed for SQL Object Annotations.
        this.dbConnection.installPlugin(new SqlObjectPlugin());
    }

    private void loadJdbcDriver() {
        try {
            Class.forName(DatabaseConfig.getInstance().getString("db.jdbc.driver"));
        } catch (ClassNotFoundException e){
            ErrorLog.getLogger().error("The JDBC driver could not be found. " +
                    "Check that 'db.jdbc.driver' in database.properties is valid.");
        }
    }

    public Jdbi getDbConnection() {
        return this.dbConnection;
    }

    /**
     * Retrieves the database name from the JDBC URL.
     * @return the database name.
     */
    public String getDatabaseName() {
        String[] splitURL = this.dbUrl.split("/");

        return splitURL[splitURL.length - 1];
    }

    /**
     * Retrieves the port number for the database from the JDBC URL.
     * @return the database port number.
     */
    public String getPortNumber() {
        String[] splitURL = this.dbUrl.split("/");

        return splitURL[2].split(":")[1];
    }

    /**
     * Retrieves the database hostname from the JDBC URL.
     * @return the database hostname.
     */
    public String getDatabaseHost() {
        String[] splitURL = this.dbUrl.split("/");

        return splitURL[2].split(":")[0];
    }

    /**
     *  If DatabaseConnection hasn't been initialized yet, a new object will be created. Otherwise the single permitted
     *  instance of DatabaseConnection will be returned.
     * @return the single instance of DatabaseConnection
     */
    public static DatabaseConnection getInstance() {
        if (instance == null) {
            instance = new DatabaseConnection();
        }

        return instance;
    }
}