/*
* jPOS Project [http://jpos.org]
* Copyright (C) 2000-2014 Alejandro P. Revilla
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.jpos.tpl;
import org.jpos.core.Configurable;
import org.jpos.core.Configuration;
import org.jpos.core.ConfigurationException;
import org.jpos.util.LogEvent;
import org.jpos.util.LogSource;
import org.jpos.util.Logger;
import org.jpos.util.NameRegistrar;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Vector;
/** A class for preallocating, recycling, and managing
* JDBC connections.
* <P>
* Taken from Core Servlets and JavaServer Pages
* from Prentice Hall and Sun Microsystems Press,
* http://www.coreservlets.com/.
* © 2000 Marty Hall; may be freely used or adapted.
* @author Rajal Shah
* @version $Revision$ $Date$
*/
@SuppressWarnings("unchecked")
public class ConnectionPool implements Runnable, LogSource, Configurable {
Configuration cfg;
Logger logger;
String realm;
private String driver, url, username, password;
private int maxConnections;
private boolean waitIfBusy;
private Vector availableConnections, busyConnections;
private boolean connectionPending = false;
/**
* no args constructor
*/
public ConnectionPool () {
super();
}
public void setConfiguration (Configuration cfg)
throws ConfigurationException
{
this.cfg = cfg;
initEngine();
}
private void initEngine () throws ConfigurationException {
initJDBC();
}
private void initJDBC() throws ConfigurationException {
try {
Class.forName(cfg.get("jdbc.driver")).newInstance();
} catch (Exception e) {
throw new ConfigurationException (e);
}
driver = cfg.get("jdbc.driver");
url = cfg.get("jdbc.url");
username = cfg.get("jdbc.user");
password = cfg.get("jdbc.password");
int initialConnections = cfg.getInt("initial-connections");
maxConnections = cfg.getInt("max-connections");
waitIfBusy = cfg.getBoolean("wait-if-busy");
if (initialConnections > maxConnections) {
initialConnections = maxConnections;
}
availableConnections = new Vector(initialConnections);
busyConnections = new Vector();
for(int i=0; i<initialConnections; i++) {
try {
availableConnections.addElement(makeNewConnection());
} catch(SQLException e) {
throw new ConfigurationException(e);
}
}
}
/**
* To invoke the Connection Pool object directly without jPOS.
*/
public ConnectionPool(String driver, String url,
String username, String password,
int initialConnections,
int maxConnections,
boolean waitIfBusy)
throws SQLException
{
this.driver = driver;
this.url = url;
this.username = username;
this.password = password;
this.maxConnections = maxConnections;
this.waitIfBusy = waitIfBusy;
if (initialConnections > maxConnections) {
initialConnections = maxConnections;
}
availableConnections = new Vector(initialConnections);
busyConnections = new Vector();
for(int i=0; i<initialConnections; i++) {
availableConnections.addElement(makeNewConnection());
}
}
public synchronized Connection getConnection()
throws SQLException
{
if (!availableConnections.isEmpty()) {
Connection existingConnection =
(Connection)availableConnections.lastElement();
int lastIndex = availableConnections.size() - 1;
availableConnections.removeElementAt(lastIndex);
// If connection on available list is closed (e.g.,
// it timed out), then remove it from available list
// and repeat the process of obtaining a connection.
// Also wake up threads that were waiting for a
// connection because maxConnection limit was reached.
if (existingConnection.isClosed()) {
notifyAll(); // Freed up a spot for anybody waiting
return(getConnection());
} else {
busyConnections.addElement(existingConnection);
return(existingConnection);
}
} else {
// Three possible cases:
// 1) You haven't reached maxConnections limit. So
// establish one in the background if there isn't
// already one pending, then wait for
// the next available connection (whether or not
// it was the newly established one).
// 2) You reached maxConnections limit and waitIfBusy
// flag is false. Throw SQLException in such a case.
// 3) You reached maxConnections limit and waitIfBusy
// flag is true. Then do the same thing as in second
// part of step 1: wait for next available connection.
if ((totalConnections() < maxConnections) && !connectionPending) {
makeBackgroundConnection();
} else if (!waitIfBusy && !connectionPending) {
throw new SQLException("Connection limit reached");
}
// Wait for either a new connection to be established
// (if you called makeBackgroundConnection) or for
// an existing connection to be freed up.
try {
wait();
} catch (InterruptedException ie) {}
// Someone freed up a connection, so try again.
return(getConnection());
}
}
// You can't just make a new connection in the foreground
// when none are available, since this can take several
// seconds with a slow network connection. Instead,
// start a thread that establishes a new connection,
// then wait. You get woken up either when the new connection
// is established or if someone finishes with an existing
// connection.
private void makeBackgroundConnection() {
connectionPending = true;
try {
Thread connectThread = new Thread(this,"ConnectionPool-connect");
connectThread.start();
} catch(OutOfMemoryError oome) {
// Give up on new connection
}
}
public void run() {
Connection connection = null;
while (connection == null) {
try {
connection = makeNewConnection();
synchronized(this) {
availableConnections.addElement(connection);
connectionPending = false;
notifyAll();
}
} catch(Exception e) { // SQLException or OutOfMemory
LogEvent evt = new LogEvent (this, "error");
evt.addMessage ("An error occurred while trying to make a background connection");
evt.addMessage (e);
Logger.log (evt);
try {
Thread.sleep (3000); // don't get too crazy about retrying
} catch (InterruptedException ie) {
// this one, we don't care.
}
}
}
}
// This explicitly makes a new connection. Called in
// the foreground when initializing the ConnectionPool,
// and called in the background when running.
private Connection makeNewConnection()
throws SQLException {
try {
// Load database driver if not already loaded
Class.forName(driver);
// Establish network connection to database
Connection connection =
DriverManager.getConnection(url, username, password);
return(connection);
} catch(ClassNotFoundException cnfe) {
// Simplify try/catch blocks of people using this by
// throwing only one exception type.
throw new SQLException("Can't find class for driver: " +
driver);
}
}
public synchronized void free(Connection connection) {
if(busyConnections.removeElement(connection)) {
availableConnections.addElement(connection);
}
// Wake up threads that are waiting for a connection
notifyAll();
}
public synchronized int totalConnections() {
return(availableConnections.size() + busyConnections.size());
}
public synchronized int getTotalConnections(){
return (availableConnections.size() + busyConnections.size());
}
/** Close all the connections. Use with caution:
* be sure no connections are in use before
* calling. Note that you are not <I>required</I> to
* call this when done with a ConnectionPool, since
* connections are guaranteed to be closed when
* garbage collected. But this method gives more control
* regarding when the connections are closed.
*/
public synchronized void closeAllConnections() {
closeConnections(availableConnections);
availableConnections = new Vector();
closeConnections(busyConnections);
busyConnections = new Vector();
}
private void closeConnections(Vector connections) {
try {
for(int i=0; i<connections.size(); i++) {
Connection connection = (Connection)connections.elementAt(i);
if (!connection.isClosed()) {
connection.close();
}
}
} catch(SQLException sqle) {
// Ignore errors; garbage collect anyhow
}
}
public synchronized String toString() {
String info =
"ConnectionPool(" + url + "," + username + ")" +
", available=" + availableConnections.size() +
", busy=" + busyConnections.size() +
", max=" + maxConnections;
return(info);
}
public void setLogger (Logger logger, String realm) {
this.logger = logger;
this.realm = realm;
}
public String getRealm () {
return realm;
}
public Logger getLogger() {
return logger;
}
/**
* @return ISOMUX instance with given name.
* @throws NameRegistrar.NotFoundException;
* @see NameRegistrar
*/
public static ConnectionPool getConnectionPool (String name)
throws NameRegistrar.NotFoundException
{
return (ConnectionPool) NameRegistrar.get ("connection.pool."+name);
}
}