Error while setting values from a database to a drop down list

[Sridhar Venkataraman]

Hi all,

I have a JSP page with a drop down list that is to be populated with values from a database.

This is the code in my JSP file:

 <!-- Form for picking the floor -->
 
<!-- Get the available floors -->
<% ArrayList<Integer> floornumbers = dataManager.getAllFloorNumbers();
   Iterator<Integer> iterator = floornumbers.iterator(); %>
 
<!-- Create the form for users to select the floor -->
<form id="floorselectionform">
<input type="hidden" name="action" value="floorselected"/> <!-- Guides the servlet to redirect to the appropriate page -->
Select floor | <select name="floorselector" id="floorselector">
<% while (iterator.hasNext()) { %>
<option value="<%=iterator.next().intValue()%>"> <%=iterator.next().intValue()%> </option>
<% } %>
</select>
<input type="submit" value="Go!"/>
</form>   

The DataManager.java class simply forwards this to its respective Peer class, which has the code shown below:

  package seatplanner.model;
 
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
 
/* This class handles all floor operations */
 
 public class FloorPeer
 {
 
 /* This method returns all the floor numbers */
 public static ArrayList<Integer> getAllFloorNumbers(DataManager dataManager) {
    ArrayList<Integer> floornumbers = new ArrayList<Integer>();
    Connection connection = dataManager.getConnection();
    if (connection != null) {
      try {
        Statement s = connection.createStatement();
        String sql = "select ID from floor order by ID asc";
        try {
          ResultSet rs = s.executeQuery(sql);
          try {
            while (rs.next()) {
              floornumbers.add(rs.getInt(1));
              }
            }
          finally { rs.close(); }
          }
        finally {s.close(); }
        }
      catch (SQLException e) {
        System.out.println("Could not get floor numbers: " + e.getMessage());
        }
      finally {
        dataManager.putConnection(connection);
        }
      }
    return floornumbers;
    }
 }  

The classes compile properly, but when I load this page up in Tomcat it just freezes and does not load the form. I tested the DB connection and it works fine.

What am I doing wrong in the JSP code?

Thanks for the help in advance.

UPDATE: I commented out the form, and added <%=floornumbers.size()%> right above the commented code to check if the ArrayList is indeed getting populated with the values from the database (the values are of type integer in the database). The page still freezes like before. I'm puzzled now .
[ January 11, 2008: Message edited by: Sridhar Venkataraman ]

[Ben Souther]

Not sure if this is the problem but, is this what you really want?

<% while (iterator.hasNext()) { %>
  <option value="<%=iterator.next().intValue()%>"> <%=iterator.next().intValue()%> </option>
<% } %>

Each call to iterator.next(), pops off the next value in the list.
So, if you had a list containing "1", "2", "3", "4", "5",
your options would look like:

<option value="1">2</option>
<option value="3">4</option>
<option value="5">OOPs... there are no more values in the list..

[Sridhar Venkataraman]

Originally posted by Ben Souther:
Not sure if this is the problem but, is this what you really want?

<% while (iterator.hasNext()) { %>
  <option value="<%=iterator.next().intValue()%>"> <%=iterator.next().intValue()%> </option>
<% } %>

Each call to iterator.next(), pops off the next value in the list.
So, if you had a list containing "1", "2", "3", "4", "5",
your options would look like:

<option value="1">2</option>
<option value="3">4</option>
<option value="5">OOPs... there are no more values in the list..

Now that you've mentioned it, what I really wanted was:

<option value="1"> 1 </option>

and so on....

I can fix that easy. But why doesn't the code work? There seems to be no error with the DB connection or the query, and yet the page doesn't render.

[Ben Souther]

Have you confirmed that nothing is coming from the server?

Sometimes, when looking at a blank screen, using the browser's view source feature shows that there is actually output but an error in the html keeps it from rendering.

[Ben Souther]

Also, you haven't shown us the DataManager class or the code that instanciates it. Is there a useBean tag somewhere on the JSP?

Have you looked at your server's logs to see if any exceptions are being thrown?

[Sridhar Venkataraman]

Hi,

I have solved this issue. I did not use iterator in the right way, though it was only a shave
[ January 12, 2008: Message edited by: Bear Bibeault ]

[Sridhar Venkataraman]

Am I supposed to begin a new topic with the part of the message that was edited out?

[Bear Bibeault]

Yes, and please do not move the conversation to another site and post links to it.

[Sridhar Venkataraman]

All right. I participate in many forums, so I just thought it'd be easier this way.