Class LoginServlet not a Servlet?

[Alan Shiers]

Hi there,

I created a servlet called LoginServlet which extends HttpServlet. It has
the usual doGet() and doPost() methods. It compiles fine but when I try to
access it, Tomcat throws a ServletException saying my "Class LoginServlet is
not a Servlet". How absurd is that?

Any ideas as to what's going on? StackTrace and Class code is below. I
compiled using JVM 1.5. Using Tomcat 5.5.4.

Thanks,

Alan

INFO: Server startup in 13597 ms
12-Jan-2005 5:00:16 PM org.apache.catalina.core.ApplicationContext log
INFO: Marking servlet LoginServlet as unavailable
12-Jan-2005 5:00:16 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Allocate exception for servlet LoginServlet
javax.servlet.ServletException: Class LoginServlet is not a Servlet
at
org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:10
15)
at
org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:711)
at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.ja
va:131)
at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.ja
va:178)
at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126
)
at
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105
)
at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java
:107)
at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:300)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:383)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:743)
at
org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:675)
at org.apache.jk.common.SocketConnection.runIt(ChannelSocket.java:866)
at
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.jav
a:684)
at java.lang.Thread.run(Thread.java:595)

*****************************************************************

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import javax.naming.*;
import javax.sql.*;
import java.sql.*;
 
public class LoginServlet extends HttpServlet
{
    HttpSession session = null;
    Vector<String> users = new Vector<String>(20);
 
    //Get the list of valid users for this application
    //from the database.
    public void initialize()
    {
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;
 
        try
       {
 
            Context ctx = new InitialContext();
            if(ctx == null )
               throw new Exception("No Context available...");
 
            DataSource ds =
(DataSource)ctx.lookup("java:comp/env/jdbc/Web101");
 
            if (ds != null)
            {
               connection = ds.getConnection();
               if(connection != null)
               {
                 statement = connection.createStatement();
                 resultSet = statement.executeQuery("SELECT STUDENT_ID FROM
STUDENTS;");
                 while(resultSet.next())
                 {
 
users.add(String.valueOf(resultSet.getInt("STUDENT_ID")));
                 }
                 users.trimToSize();
 
                 resultSet.close();
                 resultSet = null;
                 statement.close();
                 statement = null;
                 connection.close();
                 connection = null;
               }
           }
           else
           {
             throw new Exception("DataSource is null");
             //System.err.println("DataSource is null");
           }
       }
       catch(SQLException sqle)
       {
          System.err.println("SQL Problem: " + sqle.getMessage());
          System.err.println("SQL State: " + sqle.getSQLState());
          System.err.println("Vendor Error: " + sqle.getErrorCode());
       }
       catch(Exception e)
       {
          System.err.println(e.getMessage());
      }
      finally
      {
          // Always make sure result sets and statements are closed,
          // and the connection is returned to the pool
          if (resultSet != null)
          {
            try { resultSet.close(); } catch (SQLException e) { ; }
            resultSet = null;
          }
          if (statement != null)
          {
            try { statement.close(); } catch (SQLException e) { ; }
            statement = null;
          }
          if (connection != null)
          {
            try { connection.close(); } catch (SQLException e) { ; }
            connection = null;
          }
       }
 
     }
 
    public void doGet(HttpServletRequest req, HttpServletResponse res)throws
ServletException, IOException
    {
         doPost(req,res);
    }
 
    public void doPost(HttpServletRequest req, HttpServletResponse
res)throws ServletException, IOException
    {
        session = req.getSession();
        initialize();
 
        String studentid = req.getParameter("studentid");
 
        try
        {
           if(studentid != null)
           {
             //Iterate over the Vector users to find a match
             String id = "";
             boolean valid_user = false;
             for(int i = 0; i < users.size(); i++)
             {
                id = (String)users.get(i);
                if(id.equals(studentid))
                {
                   valid_user = true;
                   break;
                }
             }
 
             if(valid_user)
            {
                req.setAttribute("studentid", studentid);
                ServletContext ct = getServletContext();
                RequestDispatcher rd =
ct.getRequestDispatcher("/MarksServlet");
                rd.forward(req, res);
                return;
            }
            else
            {
                PrintWriter out = res.getWriter();
                out.println(ServletUtilities.headWithTitle("Login Servlet")
+
                "<body>\n" +
                "<br><h2>Invalid Student Identification.</h2>" +
                "Use your <b>\"Back\"</b> button to return to the login
page." +
               "\n</body>\n</html>");
             }
        }
        else
        {
              PrintWriter out = res.getWriter();
             out.println(ServletUtilities.headWithTitle("Login Servlet") +
             "<body>\n" +
             "<br><h2>Invalid Student Identification.</h2>" +
             "Use your <b>\"Back\"</b> button to return to the login page."
+
             "</body>\n</html>");
         }
     }
     catch(NullPointerException npe)
     {
           PrintWriter out = res.getWriter();
           out.println(ServletUtilities.headWithTitle("Login Servlet") +
           "<body>\n" +
           "<br><h2>Invalid Student Identification.</h2>" +
           "Use your <b>\"Back\"</b> button to return to the login page." +
           "</body>\n</html>");
       }
       catch(Exception e)
       {
            System.err.println(e.getMessage());
       }
    }
}

[Adeel Ansari]

what about your web.xml ??

[Alan Shiers]

Here it is. Not a lot to it:

<?xml version="1.0" encoding="ISO-8859-1"?>
 
<!DOCTYPE web-app
    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
    "http://java.sun.com/dtd/web-app_2_3.dtd">
 
<web-app>
 
    <description>Web101 Web Development App</description>
    
    <context-param>
        <param-name>Alan Shiers</param-name>
<param-value>[e-mail]</param-value>
    </context-param>
 
    <servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>LoginServlet</servlet-class>
    </servlet>
 
    <servlet>
<servlet-name>MarksServlet</servlet-name>
<servlet-class>MarksServlet</servlet-class>
    </servlet>
 
    <servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
    </servlet-mapping>
 
    <servlet-mapping>
<servlet-name>MarksServlet</servlet-name>
<url-pattern>/MarksServlet</url-pattern>
    </servlet-mapping>
 
    <session-config>
        <!-- Value is in minutes -->
<session-timeout>15</session-timeout>
    </session-config>
 
    <resource-ref>
      <description>DB Connection</description>
      <res-ref-name>jdbc/Web101</res-ref-name>
      <res-type>javax.sql.DataSource</res-type>
      <res-auth>Container</res-auth>
    </resource-ref>
    
</web-app>
 

[Adeel Ansari]

It looks fine to me. May be someone else would find the culprit.

[Jim Chrystal]

Prefix your servlet class with the full package name, i.e., com.somepackage.MarksServlet

- Jim