poolmanager.java

Java Database connection pool

/*
 *  PoolMan Java Object Pooling and Caching Library
 *  Copyright (C) 1999-2001 The Code Studio
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  The full license is located at the root of this distribution
 *  in the LICENSE file.
 */
package com.codestudio.util;

import com.codestudio.PoolManConstants;

import java.io.Serializable;
import java.util.Enumeration;
import java.util.Hashtable;


/**
 * An object that manages several pools of objects.
 * @see SQLManager
 */
public class PoolManager implements Serializable {

    protected Hashtable pools;
    protected ObjectPool defaultpool;

    protected PoolManager() {
        this.pools = new Hashtable(1);
        this.defaultpool = null;
    }

    public Enumeration getAllPoolnames() {
        return pools.keys();
    }

    public ObjectPool getPool(String name) {

        if (name == null)
            return this.defaultpool;

        if (pools.containsKey(name)) {
            try {
                return (ObjectPool) pools.get(name);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        throw new NullPointerException("ERROR: Could not locate " + name +
                                       ". This usually means that the " +
                                       PoolManConstants.XML_CONFIG_FILE +
                                       " file could not be found, or that it " +
				       "does not contain configuration data for a " +
				       "pool with a name equal to " + name);
    }

    public void addPool(String id, ObjectPool newpool) {
        if (this.pools.containsKey(id)) {
            System.out.println("ERROR: A pool identified by the id " + id +
                               " already exists, ignoring it.");
        }
        else {
            this.pools.put(id, newpool);
            if (this.defaultpool == null)
                this.defaultpool = newpool;
        }
    }

    public void removePool(String id) {
        if (pools.containsKey(id)) {
            int th = this.defaultpool.hashCode();
            int oh = pools.get(id).hashCode();
            if (th == oh)
                this.defaultpool = null;
            pools.remove(id);
        }
    }

    public Object requestObject() {
        try {
            return defaultpool.checkOut();
        } catch (Exception e) {
            System.out.println("ERROR: Could not request object, returning NULL:");
        }
        return null;
    }

    public Object requestObject(String poolname) {
        ObjectPool pool = null;
        try {
            pool = (ObjectPool) pools.get(poolname);
        } catch (NullPointerException ne) {
        }
        if (pool != null) {
            try {
                return pool.checkOut();
            } catch (Exception e) {
                System.out.println("ERROR: Could not request object, returning NULL:");
            }
        }
        return null;
    }

    public void returnObject(Object o) {
        defaultpool.checkIn(o);
    }

    public void returnObject(Object o, String poolname) {
        ObjectPool pool = null;
        try {
            pool = (ObjectPool) pools.get(poolname);
        } catch (NullPointerException ne) {
        }
        if (pool != null)
            pool.checkIn(o);
    }

    public void destroyPools() {
        if (this.pools != null) {
            for (Enumeration enum = pools.keys(); enum.hasMoreElements();) {
                Object key = enum.nextElement();
                ObjectPool pool = (ObjectPool) pools.get(key);
                pool.closeAllResources();
            }
        }
    }
}