public class OracleConnectionManager {

private DBConnectionManager connMgr;
private final String poolName="Oracle";
private Connection conn;

public OracleConnectionManager() {

String userID = "system";
String password = "manager";
String JDBCDriver = "oracle.jdbc.driver.OracleDriver";
String JDBCDriverType = "jdbc:oracle:thin";
String DBHost = "127.0.0.1";
String Port = "1521";
String SID="sid";
String url = JDBCDriverType+":@"+DBHost + ":" + Port + ":" +SID;


connMgr = DBConnectionManager.getInstance();
if (DBConnectionManager.clients == 1){
connMgr.init(poolName, JDBCDriver, url, userID, password);
connMgr.init("egongOracle", JDBCDriver, JDBCDriverType+":@110.7.6.22:1521:egong", "abcusername", "abcpasswd");


}
}

public Connection getConnection() {
return (conn=connMgr.getConnection(poolName));
}

public Connection getConnection(String newOracle) {
return (conn=connMgr.getConnection(newOracle));
}


public void freeConnection() {
connMgr.freeConnection(poolName,conn);
}

public void freeConnection(String newOracle) {
connMgr.freeConnection(newOracle,conn);
}

}


public class DBConnectionManager {
static private DBConnectionManager instance=null; // The single instance
static public int clients=0;

private Vector drivers = new Vector();
private PrintWriter log;
private Hashtable pools = new Hashtable();
private final int MAX_CONN = 1000;

/**
* Returns the single instance, creating one if it´s the
* first time this method is called.
*
* @return DBConnectionManager The single instance.
*/
static synchronized public DBConnectionManager getInstance() {
if (instance == null) {
instance = new DBConnectionManager();
}
clients++;
return instance;
}

/**
* A private constructor since this is a Singleton
*/
private DBConnectionManager() {
// init();
}

/**
* Returns a connection to the named pool.
*
* @param name The pool name as defined in the properties file
* @param con The Connection
*/
public void freeConnection(String name, Connection con) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
pool.freeConnection(con);
}
}

/**
* Returns an open connection. If no one is available, and the max
* number of connections has not been reached, a new connection is
* created.
*
* @param name The pool name as defined in the properties file
* @return Connection The connection or null
*/
public Connection getConnection(String name) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
return pool.getConnection();
}
return null;
}

/**
* Returns an open connection. If no one is available, and the max
* number of connections has not been reached, a new connection is
* created. If the max number has been reached, waits until one
* is available or the specified time has elapsed.
*
* @param name The pool name as defined in the properties file
* @param time The number of milliseconds to wait
* @return Connection The connection or null
*/
public Connection getConnection(String name, long time) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
return pool.getConnection(time);
}
return null;
}

/**
* Closes all open connections and deregisters all drivers.
*/
public synchronized void release() {
// Wait until called by the last client
if (--clients != 0) {
return;
}

Enumeration allPools = pools.elements();
while (allPools.hasMoreElements()) {
DBConnectionPool pool = (DBConnectionPool) allPools.nextElement();
pool.release();
}
Enumeration allDrivers = drivers.elements();
while (allDrivers.hasMoreElements()) {
Driver driver = (Driver) allDrivers.nextElement();
try {
DriverManager.deregisterDriver(driver);
log("Deregistered JDBC driver " + driver.getClass().getName());
}
catch (SQLException e) {
log(e, "Can´t deregister JDBC driver: " + driver.getClass().getName());
}
}
log.close();
}

/**
* Creates instances of DBConnectionPool based on the properties.
* A DBConnectionPool can be defined with the following properties:
*

* .url The JDBC URL for the database
* 
.user A database user (optional)
* .password 
A database user password (if user specified)
* .maxconn The 
maximal number of connections (optional)
* 

*
* @param props The connection pool properties
*/
private void createPools(String poolName, String url, String user, String password, int max) {
/*
Enumeration propNames = props.propertyNames();
while (propNames.hasMoreElements()) {
String name = (String) propNames.nextElement();
if (name.endsWith(".url")) {
String poolName = name.substring(0, name.lastIndexOf("."));
String url = props.getProperty(poolName + ".url");
if (url == null) {
log("No URL specified for " + poolName);
continue;
}
String user = props.getProperty(poolName + ".user");
String password = props.getProperty(poolName + ".password");
String maxconn = props.getProperty(poolName + ".maxconn", "0");
int max;
try {
max = Integer.valueOf(maxconn).intValue();
}
catch (NumberFormatException e) {
log("Invalid maxconn value " + maxconn + " for " + poolName);
max = 0;
}
DBConnectionPool pool =
new DBConnectionPool(poolName, url, user, password, max);
pools.put(poolName, pool);
log("Initialized pool " + poolName);
}
}
*/
DBConnectionPool pool =
new DBConnectionPool(poolName, url, user, password, max);
pools.put(poolName, pool);
log("Initialized pool " + poolName);
}

public void init(String poolName, String driver, String url, String user, String passwd) {
init(poolName, driver, url, user, passwd, MAX_CONN);
}

/**
* Loads properties and initializes the instance with its values.
*/
public void init(String poolName, String driver, String url, String user, String passwd, int maxconn) {
/*
InputStream is = getClass().getResourceAsStream("/db.properties");
Properties dbProps = new Properties();
try {
dbProps.load(is);
}
catch (Exception e) {
System.err.println("Can´t read the properties file. " +
"Make sure db.properties is in the CLASSPATH");
return;
}
String logFile = dbProps.getProperty("logfile", "DBConnectionManager.log");

String logFile = "." + File.separator + "logs" + File.separator + "dbpool";
try {
log = new PrintWriter(new FileWriter(logFile, true), true);
}
catch (IOException e) {
System.err.println("Can´t open the log file: " + logFile);
log = new PrintWriter(System.err);
}
*/
log = new PrintWriter(System.err);
loadDrivers(driver);
createPools(poolName, url, user, passwd, maxconn);
}

/**
* Loads and registers all JDBC drivers. This is done by the
* DBConnectionManager, as opposed to the DBConnectionPool,
* since many pools may share the same driver.
*
* @param props The connection pool properties
*/
private void loadDrivers(String driverClassName) {
/*
String driverClasses = props.getProperty("drivers");
StringTokenizer st = new StringTokenizer(driverClasses);
while (st.hasMoreElements()) {
String driverClassName = st.nextToken().trim();
try {
Driver driver = (Driver)
Class.forName(driverClassName).newInstance();
DriverManager.registerDriver(driver);
drivers.addElement(driver);
log("Registered JDBC driver " + driverClassName);
}
catch (Exception e) {
log("Can´t register JDBC driver: " +
driverClassName + ", Exception: " + e);
}
}
*/
try {
Driver driver = (Driver)
Class.forName(driverClassName).newInstance();
DriverManager.registerDriver(driver);
drivers.addElement(driver);
log("Registered JDBC driver " + driverClassName);
}
catch (Exception e) {
log("Can´t register JDBC driver: " +
driverClassName + ", Exception: " + e);
}
}

/**
* Writes a message to the log file.
*/
private void log(String msg) {
log.println(new Date() + ": " + msg);
}

/**
* Writes a message with an Exception to the log file.
*/
private void log(Throwable e, String msg) {
log.println(new Date() + ": " + msg);
e.printStackTrace(log);
}

/**
* This inner class represents a connection pool. It creates new
* connections on demand, up to a max number if specified.
* It also makes sure a connection is still open before it is
* returned to a client.
*/
class DBConnectionPool {
private int checkedOut;
private Vector freeConnections = new Vector();
private int maxConn;
private String name;
private String password;
private String URL;
private String user;

/**
* Creates new connection pool.
*
* @param name The pool name
* @param URL The JDBC URL for the database
* @param user The database user, or null
* @param password The database user password, or null
* @param maxConn The maximal number of connections, or 0
* for no limit
*/
public DBConnectionPool(String name, String URL, String user, String password,
int maxConn) {
this.name = name;
this.URL = URL;
this.user = user;
this.password = password;
this.maxConn = maxConn;
}

/**
* Checks in a connection to the pool. Notify other Threads that
* may be waiting for a connection.
*
* @param con The connection to check in
*/
public synchronized void freeConnection(Connection con) {
// Put the connection at the end of the Vector
freeConnections.addElement(con);
checkedOut--;
notifyAll();
}

/**
* Checks out a connection from the pool. If no free connection
* is available, a new connection is created unless the max
* number of connections has been reached. If a free connection
* has been closed by the database, it´s removed from the pool
* and this method is called again recursively.
*/
public synchronized Connection getConnection() {
Connection con = null;
if (freeConnections.size() > 0) {
// Pick the first Connection in the Vector
// to get round-robin usage
con = (Connection) freeConnections.firstElement();
freeConnections.removeElementAt(0);
try {
if (con.isClosed()) {
log("Removed bad connection from " + name);
// Try again recursively
con = getConnection();
}
}
catch (SQLException e) {
log("Removed bad connection from " + name);
// Try again recursively
con = getConnection();
}
}
else if (maxConn == 0 || checkedOut < maxConn) {
con = newConnection();
}
if (con != null) {
checkedOut++;
}
return con;
}

/**
* Checks out a connection from the pool. If no free connection
* is available, a new connection is created unless the max
* number of connections has been reached. If a free connection
* has been closed by the database, it´s removed from the pool
* and this method is called again recursively.
*

* If no connection is available and the max number has been
* reached, this method waits the specified time for one to be
* checked in.
*
* @param timeout The timeout value in milliseconds
*/
public synchronized Connection getConnection(long timeout) {
long startTime = new Date().getTime();
Connection con;
while ((con = getConnection()) == null) {
try {
wait(timeout);
}
catch (InterruptedException e) {}
if ((new Date().getTime() - startTime) >= timeout) {
// Timeout has expired
return null;
}
}
return con;
}

/**
* Closes all available connections.
*/
public synchronized void release() {
Enumeration allConnections = freeConnections.elements();
while (allConnections.hasMoreElements()) {
Connection con = (Connection) allConnections.nextElement();
try {
con.close();
log("Closed connection for pool " + name);
}
catch (SQLException e) {
log(e, "Can´t close connection for pool " + name);
}
}
freeConnections.removeAllElements();
}

/**
* Creates a new connection, using a userid and password
* if specified.
*/
private Connection newConnection() {
Connection con = null;
try {
if (user == null) {
con = DriverManager.getConnection(URL);
}
else {
con = DriverManager.getConnection(URL, user, password);
}
log("Created a new connection in pool " + name);
}
catch (SQLException e) {
log(e, "Can´t create a new connection for " + URL);
return null;
}
return con;
}
}
}　[@more@]