Metacat

  private Hashtable connectionPool = new Hashtable();

// CONSTRUCTORS NOT NEEDED

//  /**

//   * Construct an instance of the utility class

//   */

//  public MetaCatUtil() {

//

//    options = (PropertyResourceBundle)

//          PropertyResourceBundle.getBundle(propertiesFile);

//  }

//  

//  /**

//   * This constructor allows the usage of a different properties file

//   * @param propFile the properties file that you wish to use.

//   */

//  public MetaCatUtil(String propFile)  {

//

//    propertiesFile = propFile;

//  }

  /** 

   * Utility method to establish a JDBC database connection using connection

   * info from the properties file

   */

  public Connection openDBConnection()

                throws SQLException, ClassNotFoundException {

    return openDBConnection(getOption("dbDriver"), getOption("defaultDB"),

                     getOption("user"), getOption("password"));

  }

  /** 

   * Utility method to establish a JDBC database connection 

   *

   * @param dbDriver the string representing the database driver

   * @param connection the string representing the database connectin parameters

   * @param user name of the user to use for database connection

   * @param password password for the user to use for database connection

   */

  public static Connection openDBConnection(String dbDriver, String connection,

                String user, String password)

                throws SQLException, ClassNotFoundException {

     // Load the Oracle JDBC driver

     Class.forName (dbDriver);

     debugMessage("Opening connection: " + connection);

     // Connect to the database

     Connection conn = DriverManager.getConnection( connection, user, password);

     return conn;

  }

  /* Utility method to create and return a pool of Connection objects */

  public Hashtable getConnectionPool()

                throws SQLException, ClassNotFoundException {

    int initConn = (new Integer(getOption("initialConnections"))).intValue();

    for ( int i = 0; i < initConn; i++ ) {

        connectionPool.put( openDBConnection(), Boolean.FALSE );

    }    

    return connectionPool;

  }

  /* Utility method to get a unused Connection object from the pool */

  public Connection getConnection()

                throws SQLException, ClassNotFoundException, Exception 

  {

    Connection conn = null;

    Enumeration connections = connectionPool.keys();

    synchronized (connectionPool) {

      while (connections.hasMoreElements()) {

        conn = (Connection)connections.nextElement();

        Boolean b = (Boolean)connectionPool.get(conn);

        if (conn == null || conn.isClosed()) {

            // closed connection; replace it

            conn = openDBConnection();

            // update the pool to show this one taken

            connectionPool.put(conn, Boolean.TRUE);  

            return conn;

        } else if (b == Boolean.FALSE) {

            // unused connection; test if it works and get it

            try {

                conn.setAutoCommit(true);

            } catch (SQLException e) {

                // problem with the connection, replace it

                conn = openDBConnection();

            }    

            // update the pool to show this one taken

            connectionPool.put(conn, Boolean.TRUE);    

            return conn;

        }    

      }  

    }   

    // If we get here, there no free connections;

    // we need to make more

    int incConn = (new Integer(getOption("incrementConnections"))).intValue();

    int maxConn = (new Integer(getOption("maximumConnections"))).intValue();

    int k = connectionPool.size();

    if ( k >= maxConn ) {

        throw new Exception("The maximum of " + maxConn + 

                            " open db connections is reached." +

                            " New db connection to MetaCat" +

                            " cannot be established.");

    }    

    // decide how many new connections to open; no more than the maximum

    if ( incConn > maxConn - k ) { incConn = maxConn - k; }

    // get them

    for ( int i = 0; i < incConn; i++ ) {

        connectionPool.put( openDBConnection(), Boolean.FALSE );

    }

    // Recurse to get one of the new connections

    return getConnection();

  }

  /* Utility method to give the connection back to the pool */

  public void returnConnection (Connection returned) {

    Connection conn;

    Enumeration connections = connectionPool.keys();

    try {

      if ( (returned != null) && !(returned.isClosed()) ) {

        while (connections.hasMoreElements()) {

          conn = (Connection)connections.nextElement();

          if ( conn == returned ) {

            connectionPool.put( conn, Boolean.FALSE );

            break;

          }    

        }    

      }

    } catch (SQLException e) {}    

  }

  /* Return the size of the pool */

  public int getPoolSize() {

    return connectionPool.size();

  }

  /* Utility method to close all the connection from the pool */

  public void closeConnections() {

    Connection conn;

    Enumeration connections = connectionPool.keys();

    while (connections.hasMoreElements()) {

        conn = (Connection)connections.nextElement();

        try {

            if ( (conn != null) && !(conn.isClosed()) ) {

              conn.close();

            }    

        } catch (SQLException e) {}    

    }

  }