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Chapter 18 JDBC and Database Connection Pooling

public synchronized void closeAllConnections() {

// The closeConnections method loops down Vector, calling

// close and ignoring any exceptions thrown.

closeConnections(availableConnections);

availableConnections = new Vector();

closeConnections(busyConnections);

busyConnections = new Vector();

}

The full class follows. 

Listing 18.19 ConnectionPool.java 

package coreservlets;

import java.sql.*;

import java.util.*;

/** A class for preallocating, recycling, and managing

 *  JDBC connections.

*/

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