How to test if db connection is available

Question

I have got the following code to conenct to database.
package com.db;
import java.util.*;
import java.io.*;
import java.sql.*;
import javax.servlet.http.*;
public class ConnectionManager implements HttpSessionBindingListener
  private Connection connection;
  private Statement statement;
  private String driver = "";
  private String dbURL = "";
  private String login = "";
  private String password = "";
static public void main(String[] args)
      ConnectionManager cm = new ConnectionManager();
  } // main
public ConnectionManager()
       Properties Prop = new Properties();
       try {
          InputStream configStream = getClass().getResourceAsStream("/config/database.properties");
               Prop.load(configStream);
          configStream.close();
           } catch(IOException e) {
                  System.out.println("Error: Cannot laod configuration file ");
       driver =Prop.getProperty("driver");
       dbURL = Prop.getProperty("dbURL");
        login = Prop.getProperty("login");
        password = Prop.getProperty("password");
public void setDriver (String sDriver)
   if (sDriver != null)
       driver = sDriver;
public String getDriver ()
   return driver;
public void setDbURL (String sDbURL)
    if (sDbURL != null)
     dbURL = sDbURL;
public String getDbURL()
   return dbURL;
public void setLogin (String sLogin)
   if (sLogin != null)
      login = sLogin;
public String getLogin()
   return login;
public void setPassword (String sPassword)
   if (sPassword != null)
      password = sPassword;
private String getPassword()
   return password;
private void getConn ()
   try
      Class.forName(driver);
      connection = DriverManager.getConnection(dbURL,login,password);
      statement=connection.createStatement();
   catch (ClassNotFoundException e)
      System.out.println("ConnectionManager: driver unavailable");
      connection = null;
   catch (SQLException e)
      System.out.println("ConnectionManager: driver not loaded");
      connection = null;
public Connection getConnection()
   if (connection == null)
      getConn();
   return connection;
public void commit() throws SQLException
    connection.commit();
public void rollback() throws SQLException
    connection.rollback();
public void setAutoCommit(boolean autoCommit)
    throws SQLException
    connection.setAutoCommit(autoCommit );
public ResultSet executeQuery(String sql) throws SQLException
    if (connection == null || connection.isClosed())
        getConn();
    return statement.executeQuery(sql);
public int executeUpdate(String sql) throws SQLException
    if (connection == null || connection.isClosed())
        getConn();
    return statement.executeUpdate(sql);
public void valueBound(HttpSessionBindingEvent event)
    System.err.println("ConnectionBean: in the valueBound method");
    try
      if (connection == null || connection.isClosed())
        connection = DriverManager.getConnection(dbURL,login,password);
        statement = connection.createStatement();
    catch (SQLException e)
      e.printStackTrace();
      connection = null;
public void valueUnbound(HttpSessionBindingEvent event)
    close();
public void close()
   try
       if ( connection != null
            || !connection.isClosed())
        connection.close();
   catch (SQLException e)
      e.printStackTrace();
My aim is to find out if a connection is available. so that when multiple user hit the first page, it will serve the user only when a connection is available and will display an error message if there is non.
I have tried the following with database shutdown. This still return a string regardless if any connection is available.
<%
com.db.ConnectionManager CM = new com.db.ConnectionManager();
out.println(CM);
%>Please could you suggest a way I could know if a conenction is availble.
Thank you.

Answer 1

I would propose you create a Stack of Connections POP out the Connection whenever a user requests and Push a Connection back when the User is through and releases the connection this way if you try to POP a connection which is not present you can notify the user that the Connection is not available .
Ideally the Architecture of the class should be like this :-
A Class SQLProvider
some methods within it like
getConnection [Should be a Static Method ]
return Connection
destroy etc etc
The Instance will be a Vector which will be used as a stack You can Use a Stack either . and the Connection will be a part of the Vector / Stack .
The getConnection will Pop out elements and if not present should return a Message / Exception this is to your requirements .
A Static Code snippet which will populate the Stack once with the connection etc .
Does that Gives you Idea how to write the code ?
S