the detail pool management code
DBConnectionManager.java
package com.coa.cim.database;
/**
*
Title: CIM SYSTEM
*
Description: The Customer Infomation Managment System
*
Copyright: Copyright (c) 2002
*
Company: COA Sci&Tech
* @author Mula Liu
* @version 1.0
*/
import java.sql.*;
import java.util.*;
import java.io.*;
public class DBConnectionManager {
private static DBConnectionManager instance=null;
private DBConnectionPool pool;
private static int client;
private Properties dbProps;
private Vector drivers;
public DBConnectionManager() {
init();
}
public synchronized static DBConnectionManager getInstance(){
if(instance==null){
instance=new DBConnectionManager();
}
client++;
return(instance);
} //create an instance of connection manager. if exits ,just returen the instance
void init(){
drivers=new Vector();
InputStream is=this.getClass().getResourceAsStream("../resource/Res.properties");
try{
dbProps=new Properties();
dbProps.load(is);
}catch(Exception ex){
System.out.println("Miss Resource File "+ex.getMessage());
}
loadDriver();
createPool();
} //using Properties.load() method to locate outter properties file
public void loadDriver(){
String driverClasses=dbProps.getProperty("dbDriver");
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);
}catch(Exception ex){
ex.printStackTrace();
}
}
} //parse the file, load mutil driver class in
public void createPool(){
String userName=dbProps.getProperty("dbUserName");
String password=dbProps.getProperty("dbPassword");
String url=dbProps.getProperty("connectionURL");
int maxConn;
try{
maxConn=Integer.valueOf(dbProps.getProperty("maxConnection","0")).intValue();
}catch(NumberFormatException ex){
maxConn=0;
}
pool=new DBConnectionPool(userName,password,url,maxConn);
} //parse the file, load username,password,url and maxconnection in
public synchronized int getClientCount(){
return(client);
}
public Connection getDBConnection(){
if(pool != null){
return(pool.getDBConnection());
}
return(null);
}//act as facade
public Connection getDBConnection(long timeout){
if(pool != null){
return(pool.getDBConnection(timeout));
}
return(null);
}//act as facade
public void freeDBConnection(Connection conn){
if(pool != null){
pool.freeDBConnection(conn);
}
}//act as facade
public void realse(){
if(this.client != 0){
return;
}
if(pool != null){
pool.release();
Enumeration enum=drivers.elements();
while(enum.hasMoreElements()){
Driver driver=(Driver)enum.nextElement();
try{
DriverManager.deregisterDriver(driver);
}catch(Exception ex){
System.out.println("Can not deregister driver "+driver.getClass().getName());
}
}
}
}//act as facade then de register driver
}
________________________________________
DBConnectionPool.java
package com.coa.cim.database;
/**
*
Title: CIM SYSTEM
*
Description: The Customer Infomation Managment System
*
Copyright: Copyright (c) 2002
*
Company: COA Sci&Tech
* @author Mula Liu
* @version 1.0
*/
import java.sql.*;
import java.util.*;
public class DBConnectionPool {
private String dbUserName;
private String dbPassword;
private String connectionURL;
private int maxConnection;
private Vector freeConnections;
private int checkedOut;
public DBConnectionPool(String userName,String password,String url,int maxConn) {
this.dbUserName=userName;
this.dbPassword=password;
this.connectionURL=url;
this.maxConnection=maxConn;
freeConnections=new Vector();
}// initalize
public synchronized Connection getDBConnection(){
Connection conn=null;
if(freeConnections.size() > 0){
conn=(Connection)freeConnections.elementAt(0);
freeConnections.removeElementAt(0);
try{
if(conn.isClosed()){
conn=getDBConnection();
}
}catch(SQLException ex){
conn=getDBConnection();
}
}else if(maxConnection==0 || checkedOut < maxConnection){
conn=newDBConnection();
}
if(conn!=null){
checkedOut++;
}
return(conn);
}// using FIFO method to get connection instance
public synchronized Connection getDBConnection(long timeout){
long startTime=new java.util.Date().getTime();
Connection conn;
while((conn=getDBConnection())==null){
try{
wait(timeout);
}catch(InterruptedException ex){}
if(new java.util.Date().getTime()-startTime >= timeout){
return(null);
}
}
return conn;
}
public Connection newDBConnection(){
Connection conn=null;
try{
if(dbUserName==null){
conn=DriverManager.getConnection(connectionURL);
}else{
conn=DriverManager.getConnection(connectionURL,dbUserName,dbPassword);
}
}catch(SQLException ex){
ex.printStackTrace();
}
return(conn);
}
public synchronized void freeDBConnection(Connection conn){
freeConnections.addElement(conn);
checkedOut--;
notifyAll();
}
public synchronized void release(){
Enumeration allConnections=freeConnections.elements();
while(allConnections.hasMoreElements()){
try{
Connection conn=(Connection)allConnections.nextElement();
conn.close();
}catch(SQLException ex){
ex.printStackTrace();
}
}
freeConnections.removeAllElements();
}
}
