DatabaseUtilities.java: Several general-purpose utilities discussed and used in the chapter.

package cwp;

import java.sql.*;

/** Three database utilities:

 *   1) getQueryResults. Connects to a database, executes
 *      a query, retrieves all the rows as arrays
 *      of strings, and puts them inside a DBResults
 *      object. Also places the database product name,
 *      database version, and the names of all the columns
 *      into the DBResults object. This has two versions:
 *      one that makes a new connection and another that
 *      uses an existing connection. 


 *   2) createTable. Given a table name, a string denoting
 *      the column formats, and an array of strings denoting
 *      the row values, this method connects to a database,
 *      removes any existing versions of the designated
 *      table, issues a CREATE TABLE command with the
 *      designated format, then sends a series of INSERT INTO
 *      commands for each of the rows. Again, there are
 *      two versions: one that makes a new connection and
 *      another that uses an existing connection. 


 *   3) printTable. Given a table name, this connects to
 *      the specified database, retrieves all the rows,
 *      and prints them on the standard output.
 */

public class DatabaseUtilities {
  
  /** Connect to database, execute specified query,
   *  and accumulate results into DBRresults object.
   *  If the database connection is left open (use the
   *  close argument to specify), you can retrieve the
   *  connection via DBResults.getConnection.
   */
  
  public static DBResults getQueryResults(String driver,
                                          String url,
                                          String username,
                                          String password,
                                          String query,
                                          boolean close) {
    try {
      Class.forName(driver);
      Connection connection =
        DriverManager.getConnection(url, username, password);
      return(getQueryResults(connection, query, close));
    } catch(ClassNotFoundException cnfe) {
      System.err.println("Error loading driver: " + cnfe);
      return(null);
    } catch(SQLException sqle) {
      System.err.println("Error connecting: " + sqle);
      return(null);
    }
  }

  /** Retrieves results as in previous method, but uses
   *  an existing connection instead of opening a new one.
   */
  
  public static DBResults getQueryResults(Connection connection,
                                          String query,
                                          boolean close) {
    try {
      DatabaseMetaData dbMetaData = connection.getMetaData();
      String productName =
        dbMetaData.getDatabaseProductName();
      String productVersion =
        dbMetaData.getDatabaseProductVersion();
      Statement statement = connection.createStatement();
      ResultSet resultSet = statement.executeQuery(query);
      ResultSetMetaData resultsMetaData =
        resultSet.getMetaData();
      int columnCount = resultsMetaData.getColumnCount();
      String[] columnNames = new String[columnCount];
      // Column index starts at 1 (ala SQL) not 0 (ala Java).
      for(int i=1; i