/*
*
*
* Copyright 1990-2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
* 2 only, as published by the Free Software Foundation.
*
* This program 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
* General Public License version 2 for more details (a copy is
* included at /legal/license.txt).
*
* You should have received a copy of the GNU General Public License
* version 2 along with this work; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 or visit www.sun.com if you need additional
* information or have any questions.
*/
package com.sun.cdc.io.j2me.http;
/**
* A class representing a persistent connection pool that is used by the http
* connection class to store persistent connections. Stream Connection
* Element are stored in the internal vector located in this class.
* Each stream connection element is marked when either in use or
* not. As new connections are requested - the current connections in the pool
* are searched for a match and inactivity.
*
* <p> There is a maximum number of simultaneous connections that can be
* in the pool at any one time. If for some reason there are no matching
* connections available - a new one may be created (as long as it does not
* exceed the maximum). If there number of connections in the pool exceeds
* the maximum - an adjustment is made to delete unused connections. Once
* that happens (if at all) a new connection is created. If it can not create
* a new connection an exception is raised. Once a connection is close down
* a connection must be returned to the pool as inactive for another use.
*
* <p> Each individual stream connection stream element (or container)
* includes a in-use flag. Once a connection has been taken from the pool its
* in-use flag is set to (true) and once that is closed its set to (false).
* Once the connection stream element is (false) its available for reuse.
*
*/
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.util.Vector;
import java.util.Enumeration;
import javax.microedition.io.StreamConnection;
import java.security.AccessController;
/**
* This class implements the necessary functionality for the HTTP persistent
* connection pool. This class contains individual http connection elements
* (or containers) including whether or/not a that particular connection is
* active. If a connection becomes inactive - its is available for reuse by
* another http connection session or the same one. This reduces the connection
* time for each subsequent connection.
*
* @version 1.0
*
*/
public class StreamConnectionPool {
/** How long a connection can linger after its last use. */
private long m_connectionLingerTime;
/** internal connection hash table */
private Vector m_connections;
/** maximum connections */
private int m_max_connections;
/**
* Create a new instance of this class.
* We are initially unconnected this will create the
* first connection.
*
* @param number_of_connections initial number of connections
* must greater than zero.
* @param connectionLingerTime how many milliseconds a connection should
* stay in the pool after its last use
*/
protected StreamConnectionPool(int number_of_connections,
long connectionLingerTime) {
this.m_max_connections = number_of_connections;
this.m_connectionLingerTime = connectionLingerTime;
m_connections = new Vector(m_max_connections);
}
/**
* Tries to add a reuseable connection to the connection pool.
* Replace any not in use connections to the same host and port.
* Will not add to the same host and port in use. Will replace
* oldest not in use element (if any) if the pool is full.
*
* @param p_protocol The protocol for the connection
* @param p_host The Hostname for the connection
* @param p_port The port number for the connection
* @param sc The base stream connection
* @param dos The data output stream from the base
* connection
* @param dis The data input stream from the base
* connection
*
* @return true if the connection was added, otherwise false
*/
synchronized boolean add(String p_protocol,
String p_host, int p_port, StreamConnection sc,
DataOutputStream dos, DataInputStream dis) {
StreamConnectionElement oldestNotInUse = null;
// find the last unused element
Enumeration cons = m_connections.elements();
while (cons.hasMoreElements()) {
StreamConnectionElement sce =
(StreamConnectionElement)cons.nextElement();
if (sce.m_in_use) {
if (p_host.equals(sce.m_host) && p_port == sce.m_port) {
return false;
}
continue;
}
// if the connection is a duplicate, delete it
if (p_host.equals(sce.m_host) && p_port == sce.m_port) {
// no protocol duplicates on host and port
sce.close();
m_connections.removeElement(sce);
break;
} else {
if (oldestNotInUse == null ||
sce.m_time < oldestNotInUse.m_time) {
// save the oldest not in use, it may be removed later
oldestNotInUse = sce;
}
}
}
/*
* first check and see if the maximum number of connections
* has been reached - if so delete the first one in the list (FIFO)
* or
* if this port and host are already in the pool.
*/
if (m_connections.size() >= m_max_connections) {
if (oldestNotInUse == null) {
return false;
}
oldestNotInUse.close();
m_connections.removeElement(oldestNotInUse);
}
m_connections.addElement(newElement(p_protocol, p_host, p_port, sc, dos, dis));
return true;
}
protected StreamConnection newElement(String p_protocol,
String p_host, int p_port, StreamConnection sc,
DataOutputStream dos, DataInputStream dis) {
return new StreamConnectionElement(p_protocol,
p_host, p_port, sc, dos, dis);
}
/**
* Close connection and remove an instance of the stream connection
* element from the connection pool.
*
* @param sce The stream connection element to remove
*/
synchronized void remove(StreamConnectionElement sce) {
sce.close();
m_connections.removeElement(sce);
}
/**
* get an available connection and set the boolean flag to
* true (unavailable) in the connection pool.
* Also removes any stale connections, since this method gets
* called more than add or remove.
*
* @param p_protocol The protocol for the connection
* @param p_host The Hostname for the connection
* @param p_port The port number for the connection
*
* @return A stream connection element or
* null if not found
*/
public synchronized StreamConnectionElement get(
String p_protocol, String p_host, int p_port) {
StreamConnectionElement result = null;
long c_time = System.currentTimeMillis();
Enumeration cons = m_connections.elements();
Vector connectionsToClose = new Vector();
while (cons.hasMoreElements()) {
StreamConnectionElement sce =
(StreamConnectionElement)cons.nextElement();
if ((c_time - sce.m_time) > m_connectionLingerTime) {
if (!sce.m_in_use) {
sce.close();
} else {
// signal returnToUse() to close
sce.m_removed = true;
}
// m_connections.removeElement(sce);
connectionsToClose.add(sce);
continue;
}
if (p_host.equals(sce.m_host) && p_port == sce.m_port &&
p_protocol.equals(sce.m_protocol) && !sce.m_in_use) {
result = sce;
// do not break out so old connections can be removed
continue;
}
}
for (int i = 0; i < connectionsToClose.size(); ++i) {
m_connections.removeElement(connectionsToClose.elementAt(i));
}
connectionsToClose.clear();
if (result != null) {
result.m_in_use = true;
}
return result;
}
/**
* Return an instance of the stream connection element to the
* connection pool so it can be reused. It is done in the method
* so it can be synchronized with the get method.
*
* @param returned The stream connection element to return
*/
synchronized void returnForReuse(StreamConnectionElement returned) {
returned.m_in_use = false;
if (returned.m_removed) {
// the connection was out too long
returned.close();
return;
}
returned.m_time = System.currentTimeMillis();
}
}