Jsp-servlet-bean problem

Question

Please help!
I have a servlet controller, a javabean for the data and a jsp for the view.
I cannot get the jsp using
<jsp:useBean id="pList" class="bbs.PostListCommand" scope="request" />
to access the bean data
However, when I access the bean in this way
<%@ page import="bbs.PostListCommand" %>
// html
<% bbs.PostListCommand postList = null;
synchronized(session){
     postList = (bbs.PostListCommand) session.getAttribute("PostListCommand");
     if (postList == null){ %>
          <H1>Nothing in request scope to retrieve ....</H1>
          <P>
<%     }
     else{  %>
          <TABLE border="1">
// etc
� it works
Does anyone know why the <jsp:useBean> tag does not find the bean
I have installed tomcat 4.18 and set the environmental variables etc.
Directory structure is
E:\Tomcat41\webapps\examples\WEB-INF\jsp          for jsp�s
E:\Tomcat41\webapps\examples\WEB-INF\classes\bbs     for bean and servlets
Thanks in advance for any help.
Chris

Answer 1

GrayMan - Thanks for your help.
Let me explain my problem in more detail ...
Background:
I have some servlet experience, but I am new to jsp - so sorry if this seems trivial to you ...
I have a book called bitter java by bruce tate from manning.com . I am trying to get the chapter 3 examples to work
There are three files
PostListCommand          the bean
PostListController     the servlet
PostListResults          jsp
And a new test file � PostListResults version 2 with scriptlet code to access the bean.
There are a couple of typos in the downloaded source files, but nothing that causes the main problem of not being able to access the bean data.
Program flow
Servlet instantiates new bean
Bean � gets data from db
Servlet passes bean to jsp with a forward
Jsp outputs data
I have put the files in the directories �
E:\Tomcat41\webapps\examples\WEB-INF\jsp          for jsp�s
E:\Tomcat41\webapps\examples\WEB-INF\classes\bbs     for bean and servlets
The complete source code for each file is given below.
1 I have checked the db access � that�s ok
2 I have also checked reading the bean data back in from the request scope and printing out the results from within the servlet.- ok
3 I can access the data through a scriptlet (PostListResults version 2), but not with the original PostListResults which uses <jsp:useBean>
thanks in advance, chris
PostListController.java
package bbs;
// Imports
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
// Import for commands used by this class
import bbs.PostListCommand;
public class PostListController
extends javax.servlet.http.HttpServlet
implements Serializable {
* DoGet
* Pass get requests through to PerformTask
public void doGet(
HttpServletRequest request,
HttpServletResponse response)
throws javax.servlet.ServletException, java.io.IOException {
performTask(request, response);
public void performTask(
HttpServletRequest request,
HttpServletResponse response) {
try {
PostListCommand postList = (bbs.PostListCommand) java.beans.Beans.instantiate(getClass().getClassLoader(),"bbs.PostListCommand");
postList.initialize();
postList.execute();
request.setAttribute("PostListCommand", postList);
ServletContext sc = this.getServletContext();
RequestDispatcher rd =
sc.getRequestDispatcher("/jsp/PostListResults.jsp");
rd.forward(request, response);
} catch (Throwable theException) {
theException.printStackTrace();
PostListCommand.java
package bbs;
import java.io.*;
import java.sql.*;
//import COM.ibm.db2.jdbc.*;
import java.util.*;
* Insert the type's description here.
* Creation date: (07/17/2001 5:07:55 PM)
* @author: Administrator
public class PostListCommand {
// Field indexes for command properties     
private static final int SUBJECT_COLUMN = 1;
private static final int AUTHOR_COLUMN = 2;
private static final int BOARD_COLUMN = 3;
protected Vector author = new Vector();
protected Vector subject = new Vector();
protected Vector board = new Vector();
// SQL result set
protected ResultSet result;
protected Connection connection = null;
* execute
* This is the work horse method for the command.
* It will execute the query and get the result set.
public void execute()
throws
java.lang.Exception,
java.io.IOException {
try {
// retrieve data from the database
Statement statement = connection.createStatement();
result =
statement.executeQuery("SELECT subject, author, board from posts");
while (result.next()) {
subject.addElement(result.getString(SUBJECT_COLUMN));
author.addElement(result.getString(AUTHOR_COLUMN));
board.addElement(result.getString(BOARD_COLUMN));
result.close();
statement.close();
} catch (Throwable theException) {
theException.printStackTrace();
* getAuthor
* This method will get the author property.
* Since the SQL statement returns a result set,
* we will index the result.
public String getAuthor(int index)
throws
java.lang.IndexOutOfBoundsException,
java.lang.ArrayIndexOutOfBoundsException {
return (String) author.elementAt(index);
* getBoard
* This method will get the board property.
* Since the SQL statement returns a result set,
* we will index the result.
public String getBoard(int index)
throws
java.lang.IndexOutOfBoundsException,
java.lang.ArrayIndexOutOfBoundsException {
return (String) board.elementAt(index);
* getSubject
* This method will get the subject property.
* Since the SQL statement returns a result set,
* we will index the result.
public String getSubject(int index)
throws
java.lang.IndexOutOfBoundsException,
java.lang.ArrayIndexOutOfBoundsException {
return (String) subject.elementAt(index);
* initialize
* This method will connect to the database.
public void initialize()
throws java.io.IOException {
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance();
// URL is jdbc:db2:dbname
String url = "jdbc:db2:board";
// URL is jdbc:odbc:bitter3board
String url = "jdbc:odbc:bitter3board";
// connect with default id/password
connection = DriverManager.getConnection(url);
} catch (Throwable theException) {
theException.printStackTrace();
* Insert the method's description here.
* Creation date: (07/17/2001 11:38:44 PM)
* @return int
* @exception java.lang.IndexOutOfBoundsException The exception description.
public int getSize() {
return author.size();
PostListResults.jsp
<HTML>
<HEAD>
<TITLE>Message Board Posts</TITLE>
</HEAD>
<BODY BGCOLOR=#C0C0C0>
<H1>All Messages</H1>
<P>
<jsp:useBean id="postList" class="bbs.PostListCommand" scope="request"></jsp:useBean>
<TABLE border="1">
<TR>
<TD>Subject</TD>
<TD>Author</TD>
<TD>Board</TD>
</TR>
<% for (int i=0; i < postList.getSize(); _i++) { %>
<TR> <TD><%=postList.getSubject(_i) %></TD>
<TD><%=postList.getAuthor(_i) %></TD>
<TD><%=postList.getBoard(_i) %></TD>
</TR>
<% } %>
</TABLE>
<P>
</BODY>
</HTML>
PostListResults.jsp version 2 � with scriplet code instead of useBean
<HTML>
<%@ page import="bbs.PostListCommand" %>
<!-- This file was generated by the chris -->
<HEAD>
<TITLE>Message Board Posts</TITLE>
</HEAD>
<BODY BGCOLOR=#C0C0C0>
<% bbs.PostListCommand postList = null;
synchronized(request){
     postList = (bbs.PostListCommand) request.getAttribute("PostListCommand");
     if (postList == null){ %>
          <H1>Nothing in request scope to retrieve ....</H1>
          <P>
<%     }
     else{  %>
          <TABLE border="1">
          <TR>
          <TD>Subject</TD>
          <TD>Author</TD>
          <TD>Board</TD>
          </TR>
     <% for (int i=0; i < postList.getSize(); _i++) { %>
               <TR> <TD><%=postList.getSubject(_i) %></TD>
          <TD><%=postList.getAuthor(_i) %></TD>
          <TD><%=postList.getBoard(_i) %></TD>
          </TR>
     <% } %>
          </TABLE>
<%     }
}%>
<P>
goodnight
</BODY>
</HTML>