How to make Connection Pooling in JAVA
Dear Members
I want to know that how can i make connection pooling in java and also how can i use that pool in my jsp/servlet application.
Plz Describe in Detail.
Thanks
Vasim
vasim_saiyad2000 wrote:
Dear Members
I want to know that how can i make connection pooling in java and also how can i use that pool in my jsp/servlet application.
Plz Describe in Detail.
Thanks
VasimAs the previous poster is trying to suggest, the server you use will have datasource and connection pooling support. so look up in the manual how to set it up, or do a google search. For example if you use Tomcat, look here:
http://tomcat.apache.org/tomcat-6.0-doc/jndi-datasource-examples-howto.html
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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.
public 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.
public 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();
public 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);
}///// The Calling Class is below---------/////////////////
import java.util.*;
import java.sql.*;
public class dbConnection
public static void main(String[] args)
String driver="oracle.jdbc.driver.OracleDriver";
String username="ETS";
String password="ETS";
String url="jdbc:oracle:thin:@192.168.47.10:1521:ETS";
int initialConnections=10;
int maxConnections=50;
boolean waitIfBusy=false;
Connection con=null;
Statement stmt = null;
ResultSet rs = null;
try
System.out.println("Before constructory "+new java.util.Date());
ConnectionPool pool=new ConnectionPool(driver,url,username,password,initialConnections,maxConnections,waitIfBusy);
System.out.println("After constructory "+new java.util.Date());
con=pool.makeNewConnection();
System.out.println("After Connection pool "+new java.util.Date());
String sql="select * from emp_master";
stmt = con.createStatement();
rs = stmt.executeQuery(sql);
while(rs.next()) {
int login1=rs.getInt("emp_code");
System.out.println("Employee Code is "+login1);
System.out.println("check 2");
String pass=rs.getString("PASSWORD");
System.out.println("Pass Word is "+pass);
}catch(Exception e)
System.out.println("Exception is "+e);
finally {
}I once created a connection pool programatically with Apache DBCP API. It didnt took more than 10 lines. Unforchunetly I dont have to code with me now.
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The database side of things I totally understand and have set up, but I now want to compile/run the java code examples, but don't know what is required to compile this.
I'm running Oracle 10.2.0.4 (64-bit) Enterprise Edition on a Linux (RHEL 5) PC. Java version is 1.6.0_20. Relevant .bash_profile environment variables are as follows:
export LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib
export CLASSPATH=$ORACLE_HOME/jre:$ORACLE_HOME/jlib:$ORACLE_HOME/rdbms/jlib
export PATH=$ORACLE_HOME/bin:$ORACLE_HOME/OPatch:/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin
When I try to compile, I get:
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Exception in thread "main" java.lang.NoClassDefFoundError: FastConnect/java
Caused by: java.lang.ClassNotFoundException: FastConnect.java
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
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oracle:DB10204$ cat FastConnect.java
package OSBD;
import java.sql.*;
import oracle.jdbc.pool.OracleDataSource;
public class FastConnect
public static void main(String[] args)
long connectTime=0, connectionStart=0, connectionStop=0;
long connectTime2=0, connectionStart2=0, connectionStop2=0;
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conn = cm.getConnection("KING");
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rset = stmt.executeQuery(query);
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System.out.println("Job: " + rset.getString(2));
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stmt.close();
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cm.closeConnection(conn);
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connectTime2 = (connectionStop2 - connectionStart2);
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connectTime2 + " ms.");
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I'm looking at Chapter 6.stuartu wrote:
When I try to compile, I get:
oracle:DB10204$ java FastConnect.java
Exception in thread "main" java.lang.NoClassDefFoundError: FastConnect/java
Caused by: java.lang.ClassNotFoundException: FastConnect.java
I will try to explain what is happening here.
You are launching java telling it to run a class named 'java' in a package named 'FastConnect'
and java says it cannot find that class.
What you intended to do:
$ # make the directory structure match the package structure
$ mkdir OSBD
$ # move the source file in the directory structure so it matches the package structure
$ mv FastConnect.java OSBD/
$ # compile OSBD/FastConnect.java to OSBD/FastConnect.class
$ javac OSBD/FastConnect.java
$ # launch java using the OSBD/FastConnect class
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