// Copyright (c) 1999, 2000 Oracle Corporation
package oracle.jbo.common.ampool;

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

/**
 **  This class manages the Application Pool. It is a singleton instance.
 **
 ** <a HREF="PoolMgr.txt">View implementation of PoolMgr</a>
 ** <P>
 ** @author Juan Oropeza
 **/
public class PoolMgr extends Object
{
  static PoolMgr instance = new PoolMgr();
  Hashtable poolList = new Hashtable(10);
    
  /**
  ** Constructor
  **/
  private PoolMgr()
  {
  }

  /**
  **  Retrieves the singleton instance of the Pool Manager
  **/
  static public PoolMgr getInstance()
  {
    return instance;
  }

  /**
  **  returns true if the pool has already been created.
  **/
  public synchronized boolean isPoolCreated(String sName)
  {
    if(poolList.get(sName) != null)
      return true;

    return false;
  }

  /**
  **  Returns the ApplicationPool interface for the named pool.
  **/
  public synchronized ApplicationPool getPool(String sName)
  {
    return (ApplicationPool)poolList.get(sName);
  }

  /**
  **  Removes the named pool and calls remove() function on all ApplicationModule
  **  instances that are being managed by the pool.
  **/
  public synchronized void removePool(String sName)
  {
    if(!isPoolCreated(sName))
      return;

    ApplicationPool pool = getPool(sName);

    poolList.remove(sName);

    pool.releaseInstances();
  }

  /**
  **  Create a new Application Module pool, throws an exception if the pool is already registered.
  **  The connectInfo parameter provides the necessary settings required for creating instances of
  **  Application Modules that are part of the pool. You can also specify the name of the class that
  **  implements the ApplicationPool interface. This is an important setting for users that want to provide
  **  a custom implementation of the ApplicationPool interface. The default ApplicationPool implementation is
  **  in the oracle.jbo.client.ampool.ApplicationPoolImpl class.
  **/
  public synchronized ApplicationPool createPool(String sName , String sClass, String sApplicationModule, String sConnectString, Hashtable env) throws Exception
  {
      if(isPoolCreated(sName))
      {
        throw new RuntimeException("Application Module Pool has already been created: " + sName);
      }

      Class  poolClass = Class.forName(sClass);

      ApplicationPool pool = (ApplicationPool)poolClass.newInstance();

      pool.initialize(sName, sApplicationModule, sConnectString, env);

      poolList.put(sName, pool);

      return pool;
  }


   /**
  **  Create a new Application Module pool, throws an exception if the pool is already registered.
  **  The connectInfo parameter provides the necessary settings required for creating instances of
  **  Application Modules that are part of the pool. You can also specify the name of the class that
  **  implements the ApplicationPool interface. This is an important setting for users that want to provide
  **  a custom implementation of the ApplicationPool interface. The default ApplicationPool implementation is
  **  in the oracle.jbo.client.ampool.ApplicationPoolImpl class.
  **/
  public synchronized ApplicationPool createPool(String sName , String sApplicationModule, String sConnectString, Hashtable env) throws Exception
  {
      return createPool(sName , "oracle.jbo.common.ampool.ApplicationPoolImpl", sApplicationModule, sConnectString, env);
  }
  
  /**
  **  Returns the Enumeration interface that allows you to enumerate through
  **  all the Application Pools that are registered with the Pool Manager.
  **/
  public synchronized Enumeration getPools()
  {
    return poolList.elements();
  }

}