Hi,
try this..
import java.sql.*;
import java.util.*;
/** 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.
*/
public class ConnectionPool implements Runnable {
private String driver, url, username, password;
private int maxConnections;
private boolean waitIfBusy;
private Vector availableConnections, busyConnections;
private boolean connectionPending = false;
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) {
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);
connectThread.start();
} catch(OutOfMemoryError oome) {
// Give up on new connection
}
}
public void run() {
try {
Connection connection = makeNewConnection();
synchronized(this) {
availableConnections.addElement(connection);
connectionPending = false;
notifyAll();
}
} catch(Exception e) { // SQLException or OutOfMemory
// Give up on new connection and wait for existing one
// to free up.
}
}
// 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) {
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());
}
/** 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);
}
}
-----Original Message-----
From: hua ge [mailto:[EMAIL PROTECTED]]
Sent: Monday, August 21, 2000 9:33 PM
To: [EMAIL PROTECTED]
Subject: connection pooling ---urgent!!!
Hi,
we are using connection pooling to connect to the Oracle DB from
jsp/servlets. the codes we are using is comming from oreilly, it works fine
for a while, but somehow, it has problem now. some connection will not be
created. we been debugging the code, but did not help.
is someone using the connection pool at real work project?
could you offer me the real connection pooling codes which is working at
your side? I really need to make it work ASAP at my side.
highly appreciate the big help!
Regards,
Helen
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