/* * @(#)ConnectionServlet_21 * * Copyright (c) 1998 Karl Moss. All Rights Reserved. * * You may study, use, modify, and distribute this software for any * purpose provided that this copyright notice appears in all copies. * * This software is provided WITHOUT WARRANTY either expressed or * implied. * * @author  Karl Moss * @version 1.0 * @date    20Mar99 * */package javaservlets.db;import javax.servlet.*;import javax.servlet.http.*;/** * <p>This is a simple servlet that holds a global connection * pool. The Servlet context is used to store a named attribute * (this servlet) so that other servlets have access to the * connection pool */public class ConnectionServlet_21 extends HttpServlet{  // Our connection pool.  javaservlets.jdbc.ConnectionPool m_connectionPool;  // Context attribute key  public static String KEY = "javaservlets.db.ConnectionServlet_21";  /**    * <p>Get a JDBC connection from the pool    *    * @return JDBC connection    */  public java.sql.Connection getConnection() throws Exception    {      java.sql.Connection con = null;      if (m_connectionPool != null) {        con = m_connectionPool.getConnection();      }      return con;    }  /**    * <p>Closes the given JDBC connection    *    * @param con JDBC Connection    */  public void close(java.sql.Connection con)    {      if (m_connectionPool != null) {        m_connectionPool.close(con);      }    }  /**    * <p>Initialize the servlet. This is called once when the    * servlet is loaded. It is guaranteed to complete before any    * requests are made to the servlet    *    * @param cfg Servlet configuration information    */  public void init(ServletConfig cfg)    throws ServletException    {      super.init(cfg);      // Create our connection pool      m_connectionPool = new javaservlets.jdbc.ConnectionPool();      // Initialize the connection pool. This will start all      // of the connections as specified in the connection      // pool configuration file      try {        m_connectionPool.initialize();      }      catch (Exception ex) {        // Convert the exception        ex.printStackTrace();        throw new ServletException          ("Unable to initialize connection pool");      }      // Add this servlet to the context so that other servlets      // can find us      getServletContext().setAttribute(KEY, this);    }  /**    * <p>Destroy the servlet. This is called once when the servlet    * is unloaded.    */  public void destroy()    {      // Remove the attribute from the context      getServletContext().removeAttribute(KEY);      // Tear down our connection pool if it was created      if (m_connectionPool != null) {        m_connectionPool.destroy();      }      super.destroy();    }}