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pool name in DBConnectionManager

Pavan Kumar
Greenhorn

Joined: Jan 13, 2002
Posts: 8
Hi I am using DBConnectionManager of Apache, I don't know which name I have to specify for Pool Name in properties file?
properties file is like this.
<poolname>.url The JDBC URL for the database
<poolname>.maxconn The max number of connections in the pool. 0 means no limit.
<poolname>.user The user name for the pool
<poolname>.password The corresponding password

Here I am giving the code por connection manager.

import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;
public class DBConnectionManager {
static private DBConnectionManager instance; // The single instance
private Vector drivers = new Vector();
private PrintWriter log;
private Hashtable pools = new Hashtable();
private Hashtable clients = new Hashtable();
/**
* A private constructor since this is a Singleton
*/
private DBConnectionManager()
throws SQLException {
init();
}
/**
* Returns the single instance, creating one if it's the
* first time this method is called.
*
* @return DBConnectionManager The single instance.
*/
public static synchronized DBConnectionManager getInstance()
throws SQLException
{
if (instance == null) {
instance = new DBConnectionManager();
}
return instance;
}
/**
* 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,String url,
String username,String password) throws SQLException {
if (!clients.containsKey(name))
{
createPools(name,url,username,password,0);
clients.put(name,new Integer(0));
}
int iCurr = ((Integer)clients.get(name)).intValue();
iCurr++;
clients.put(name,new Integer(iCurr));
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
return pool.getConnection();
}
return null;
}

/**
* Closes all open connections and deregisters all drivers.
*/
public synchronized void release(String name) throws SQLException {
// Wait until called by the last client
if (!clients.containsKey(name)) return;
int iCurr = ((Integer)clients.get(name)).intValue();
iCurr--;
clients.put(name,new Integer(iCurr));
if (iCurr > 0) return;
clients.remove(name);
DBConnectionPool pool = (DBConnectionPool)pools.get(name);
pool.release();
Enumeration allDrivers = drivers.elements();
while (allDrivers.hasMoreElements()) {
Driver driver = (Driver) allDrivers.nextElement();
DriverManager.deregisterDriver(driver);
}
}

private void createPools(String poolName,String url,
String username,String password,int max) {
DBConnectionPool pool =
new DBConnectionPool(poolName,url,username,password, max);
pools.put(poolName, pool);
log("Initialized pool " + poolName);
}

/**
* Loads properties and initializes the instance with its values.
*/
private void init() throws SQLException {
log = new PrintWriter(System.err);
loadDrivers();
//createPools(0);
}

/**
* 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() throws SQLException {
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
}

/**
* 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() throws SQLException {
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);
if (con.isClosed()) {
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;
}

/**
* Closes all available connections.
*/
public synchronized void release() throws SQLException {
Enumeration allConnections = freeConnections.elements();
while (allConnections.hasMoreElements()) {
Connection con = (Connection) allConnections.nextElement();
con.close();
}
freeConnections.removeAllElements();
}

/**
* Creates a new connection, using a userid and password
* if specified.
*/
private Connection newConnection() throws SQLException {
Connection con = null;
if (user == null) {
con = DriverManager.getConnection(URL);
}
else {
con = DriverManager.getConnection(URL, user, password);
}
log("Created a new connection in pool " + name);
return con;
}
}
}

regards
Hari.


pavan kuamr
Gregg Bolinger
GenRocket Founder
Ranch Hand

Joined: Jul 11, 2001
Posts: 15299
    
    6

paven,
Welcome to Javaranch! We don't have too many rules around these parts, but we do have a Naming Policy. We require a first and last name as the display name for all our members. You can change your display name here.
Thanks, and again, welcome.


GenRocket - Experts at Building Test Data
 
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