ConnectionManager.java :  » Web-Framework » anvil » anvil » database » Java Open Source

/*
 * $Id: ConnectionManager.java,v 1.8 2002/09/16 08:05:03 jkl Exp $
 *
 * Copyright (c) 2002 Njet Communications Ltd. All Rights Reserved.
 *
 * Use is subject to license terms, as defined in
 * Anvil Sofware License, Version 1.1. See LICENSE 
 * file, or http://njet.org/license-1.1.txt
 */
package anvil.database;

import java.util.Enumeration;
import java.util.Hashtable;


/**
 * Class providing interface for acquiring and
 * releasing JDBC connections.
 *
 * Usage:
 * <pre>
 *
 *   import java.sql.*;
 *   import anvil.database.*;
 *
 *   ConnectionManager manager = ...;
 
 *   PooledConnection connImpl = null;
 *   Connection conn = null;
 * 
 *   try {
 *
 *     connImpl = manager.acquire("njet");
 *     conn = (Connection)connImpl.getConnection();
 *     // do some work
 *
 *   } catch (NoConnectionPoolException e) {
 *     // handle error
 *   } catch (CannotReturnPooledConnectionException e) {
 *     // handle error
 *   } catch (SQLException e) {
 *     // It is recommended that the connection is closed in case of SQLException. 
 *     // When the connection is closed the Connection.isClosed() method returns 
 *     // false and connection will be removed from the queue by the house-keeping 
 *     // thread after a short while.
 *     if (conn!= null) {
 *       conn.close();
 *     }
 *   } finally {
 *     if (connImpl != null) {
 *       connImpl.release();
 *     }
 *   }
 *   
 * </pre>
 * 
 * @version $Revision: 1.8 $
 * @author Jani Lehtimki
 */
public class ConnectionManager  
{

  /**
   * <code>Hashtable</code> of <code>ConnectionAccessQueue</code>'s.
   */
  private Hashtable _queues = new Hashtable();


  /**
   * Constructs connection manager.
   */
  public ConnectionManager() 
  {
  }


  public boolean hasPool(String pool)
  {
    return _queues.containsKey(pool);
  }


  public void addPool(ConnectionPool pool)
  {
    ConnectionAccessQueue queue = new ConnectionAccessQueue(pool);
    _queues.put(pool.getName(), queue);
  }


  /**
   * Gets the enumeration of <code>ConnectionAccessQueues</code>.
   *
   * @return Enumeration
   * @see ConnectionAccessQueue
   */
  public Enumeration getAccessQueues() 
  {
    return _queues.elements();
  }  


  /**
   * Acquires connection of given type.
   *
   * @param connectionKey Type of connection
   * @throws NoConnectionPoolException If connectionKey was <code>null</code> 
   *   or given pool has not been configured.
   * @throws CannotReturnPooledConnectionException If connection couldn't be 
   *   constructed, propably due the acquire timeout.
   * @return Instance of <code>ConnectionManager</code>
   */
  public PooledConnection acquire(String connectionKey) 
    throws NoConnectionPoolException, CannotReturnPooledConnectionException 
  {
    return acquire(connectionKey, 0);
  }  

  /**
   * Acquires connection of given type, overriding the connection reserve timeout.
   *
   * @param connectionKey Type of connection
   * @param timeout Timeout override in seconds (if > 0)
   * @throws NoConnectionPoolException If connectionKey was <code>null</code> 
   *   or given pool has not been configured.
   * @throws CannotReturnPooledConnectionException If connection couldn't be 
   *   constructed, propably due the acquire timeout.
   * @return Instance of <code>ConnectionManager</code>
   */
  public PooledConnection acquire(String connectionKey, int timeout) 
    throws NoConnectionPoolException, CannotReturnPooledConnectionException 
  {
    if (connectionKey == null) {
      throw new NoConnectionPoolException("Key not given");
    } else {
      connectionKey = connectionKey.toLowerCase();
    }
    ConnectionAccessQueue queue = (ConnectionAccessQueue) _queues.get(connectionKey);
    if (queue == null) {
      throw new NoConnectionPoolException("With key " + connectionKey);
    }
    
    anvil.script.Context context = anvil.script.Context.getExistingInstance();
    if (context != null) {
      context.checkAcquire(connectionKey);
    }
    
    PooledConnection conn = queue.acquire(timeout * 1000);
    return conn;
  }


  /**
   * Shuts down the connection manager and all related 
   * classes. Shutdown is complete when this method finishes.
   */
  public void stop() 
  {
    ConnectionAccessQueue queue;
    Enumeration e = _queues.elements();
    while(e.hasMoreElements()) {
      queue = (ConnectionAccessQueue)e.nextElement();
      queue.stop();
    }
    _queues.clear();
  }



}