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Re: Tomcat MySQL JSPs and JavaBeans

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On Saturday, September 13, 2003 at 9:20:20 AM UTC+5:30, Jon Dellaria wrote:
> I have been working with JSP's and MySql using Tomcat. Until now it
> has been working fine. I think I am having a problem with defining my
> JDBC resource within Tomcat. I am pretty sure that my code is correct
> (but I am not certain), and the problem is with defining the resource
> in Tomcat. The error I am getting is:
> HTTP Status 500 - 
> 
> --------------------------------------------------------------------------------
> 
> type Exception report
> 
> message 
> 
> description The server encountered an internal error () that prevented
> it from fulfilling this request.
> 
> exception 
> 
> java.lang.NullPointerException
> 	at jspbook.ch5.Main.authenticate(Main.java:126)
> 	at jspbook.ch5.Main.doPost(Main.java:49)
> 	at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
> 	at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
> ....
> 
> Here is my Main.java:
> 
> package jspbook.ch5;
> 
> import javax.servlet.*;
> import javax.servlet.http.*;
> import java.io.*;
> import java.sql.*;
> import javax.naming.*;
> import javax.sql.*;
> 
> import jspbook.ch5.CustomerBean;
> 
> public class Main extends HttpServlet {
> 
> //  Connection dbCon;
>   DataSource ds;
>   HttpSession session;
> 
>   /* Initialize servlet. Use JNDI to look up a DataSource */
>   public void init() {
> 
>     try {
>       Context initCtx = new InitialContext();
>       Context envCtx = (Context) initCtx.lookup("java:comp/env");
>       ds = (DataSource) envCtx.lookup("jdbc/QuotingDB");
> //      dbCon = ds.getConnection();
>       System.out.println("executed lookup for jdbc. JON");
>     }
>     catch (javax.naming.NamingException e) {
>       System.out.println("A problem occurred while retrieving a
> DataSource object");
>       System.out.println(e.toString());
>     }
> 
>   }
> 
>   public void doPost (HttpServletRequest _req, HttpServletResponse
> _res)
>     throws ServletException, IOException {
> 
>     /* Refresh session attributes */
>     session = _req.getSession();
>     session.removeAttribute("loginError");
>     session.removeAttribute("submitError");
> 
>     String action = _req.getParameter("action");
> 
>     /* Authenticate user if request comes from login page */
>     if (action.equals("login")) {
>       String uid = _req.getParameter("UID");
>       String pwd = _req.getParameter("PWD");
>       if (authenticate(uid, pwd)) {
>         session.setAttribute("validUser", "y");
>         session.setAttribute("loginError", "n");
>         session.setAttribute("uid", uid);
>         gotoPage("/WEB-INF/jsp/ch5/census.jsp", _req, _res);
>       }
>       /* If the user login fails, then return them to the login page
> to retry */
>       else {
>         loginError(_req, _res);
>       }
>     }
> 
>     /* Record the survey data if the request comes from the survey
> form */
>     else if (action.equals("submit")) {
>       /* Make sure the user has logged in before recording the data */
>       String validUser = (String) session.getAttribute("validUser");
>       if (validUser.equals("y")) {
>         if (recordSurvey(_req)) {
>           /* Reset validUser flag and forward to ThankYou page */
>           session.removeAttribute("validUser");
>           gotoPage("/WEB-INF/jsp/ch5/thankyou.jsp", _req, _res);
>         }
>         else {
>           session.setAttribute("submitError", "y");
>           gotoPage("/ch5/login.jsp", _req, _res);
>         }
>       }
>       /* If the user did not login, then send them to the login page
> */
>       else {
>         loginError(_req, _res);
>       }
>     }
> 
>   }
> 
>   /* Send request to a different page */
>   private void gotoPage(String _page, HttpServletRequest _req,
> HttpServletResponse _res)
>     throws IOException, ServletException {
> 
>     RequestDispatcher dispatcher = _req.getRequestDispatcher(_page);
>     if (dispatcher != null)
>        dispatcher.forward(_req, _res);
> 
>   }
> 
>   /* Set error attributes in session and return to Login page */
>   private void loginError(HttpServletRequest _req, HttpServletResponse
> _res)
>     throws IOException, ServletException {
> 
>     session.setAttribute("validUser", "n");
>     session.setAttribute("loginError", "y");
>     gotoPage("/ch5/login.jsp", _req, _res);
> 
>   }
> 
>   /* Check if the user is valid */
>   private boolean authenticate(String _uid, String _pwd) {
> 
>     Connection dbCon = null;
>     ResultSet rs = null;
>     try {
> System.out.println("try");
>       dbCon = ds.getConnection();
> System.out.println("dbCon = ds.getConnection()");
>       Statement s = dbCon.createStatement();
> System.out.println("Statement s = dbCon.createStatement()");
>      rs = s.executeQuery("select * from user where id = '"
>               + _uid + "' and pwd = '" + _pwd + "'");
> System.out.println("rs = s.executeQuery");
>      return (rs.next());
>     }
>     catch (java.sql.SQLException e) {
>       System.out.println("A problem occurred while accessing the
> database.");
>       System.out.println(e.toString());
>     }
>     finally {
>       try {
>         dbCon.close();
>       }
>       catch (SQLException e) {
>         System.out.println("A problem occurred while closing the
> database.");
>         System.out.println(e.toString());
>       }
>     }
>     
>     return false;
> 
>   }
> 
>   /* Using the CustomerBean, record the data */
>   public boolean recordSurvey(HttpServletRequest _req) {
> 
>     Connection dbCon = null;
>     try {
>       dbCon = ds.getConnection();
>       CustomerBean cBean = new CustomerBean();
>       cBean.populateFromParms(_req);
>       return cBean.submit(dbCon);
>     }
>     catch (java.sql.SQLException e) {
>       System.out.println("A problem occurred while accessing the
> database.");
>       System.out.println(e.toString());
>     }
>     finally {
>       try {
>         dbCon.close();
>       }
>       catch (SQLException e) {
>         System.out.println("A problem occurred while closing the
> database.");
>         System.out.println(e.toString());
>       }
>     }
> 
>     return false;
>   }
> 
>   public void destroy() {}
> 
> }
> 
> 
> --------
> 
> Here is my web.xml
> <?xml version="1.0" encoding="ISO-8859-1"?>
> 
> <!DOCTYPE web-app
>     PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"
>     "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">
> 
> <web-app>
>     <servlet>
>         <servlet-name>
>             Main
>         </servlet-name>
>         <servlet-class>
>             jspbook.ch5.Main
>         </servlet-class>
> 	</servlet>
>     <servlet-mapping>
>         <servlet-name>
>             Main
>         </servlet-name>
>         <url-pattern>
>             /ch5/Main
>         </url-pattern>
>     </servlet-mapping>
> 	<taglib>
> 		<taglib-uri>/simple</taglib-uri>
> 		<taglib-location>/WEB-INF/tlds/simple.tld</taglib-location>
> 	</taglib>
> 	<taglib>
> 		<taglib-uri>/tableUtils</taglib-uri>
> 		<taglib-location>/WEB-INF/tlds/utils.tld</taglib-location>
> 	</taglib>
> 	<taglib>
> 		<taglib-uri>/groceries</taglib-uri>
> 		<taglib-location>/WEB-INF/tlds/groceries.tld</taglib-location>
> 	</taglib>
> 	<resource-ref>
> 	  <description>
>     	Resource reference to a factory for java.sql.Connection
> 	    instances that may be used for talking to a particular
>     	database that is configured in the server.xml file.
> 	  </description>
> 	  <res-ref-name>
> 	    jdbc/QuotingDB
> 	  </res-ref-name>
> 	  <res-type>
> 	    javax.sql.DataSource
> 	  </res-type>
> 	  <res-auth>
> 	    SERVLET
> 	  </res-auth>
> 	</resource-ref>
> </web-app>
> 
> ------------
> 
> Any help or direction will be greatly appreciated.
> 
> 
> Regards,
> 
> Jon Dellaria

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Re: Tomcat MySQL JSPs and JavaBeans ravi@virtuosonetsoft.com - 2016-10-10 04:57 -0700

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