Question

Duplicat entries in an Arraylist where data was fed in from a resultSet

Asked by: aman0711

Hi Experts,
                   I have an Arraylist which contains some text entries fed to it from the Database.

                  In my jsp page, I have javascript text slideshow which displays the content of this ArrayList.
                  My database table has 10 rows(10 messages), where as on my jsp page, every entry is duplicated 13 times. so all together 130 entries.

                 Where am I going wrong.

            Below is the small piece of code from my JSP, where I loop over the ArrayList

<script type="text/javascript">
     var count = 0;
     var notes = new Array();
      <c:forEach items="${notes}" var="current" varStatus="status">
          notes[${status.count - 1}] = "${current}";
      </c:forEach>
 

package com.si.dao;
 
import java.util.ArrayList;
import java.sql.*;
 
public class HomeNotes {
	
	   public Connection conn= null;
	    
	   private  ArrayList<String> notes;
	   
	   ResultSet rs = null;
	   Statement stmt = null;
	   
	   
	   int count;
	      
	     public ArrayList getNotes() throws SQLException {
	    	 
	    	  DbJDBC db = new DbJDBC();
	    	  
	    	  Connection conn = db.getConnection();
	    	  
	    	  String sql = "SELECT NOTE FROM WEB_NOTES";
	    	  try {
				 stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
				
				rs = stmt.executeQuery(sql);
				
				notes = new ArrayList<String>();
				
				rs.last();
				
				count = rs.getRow();
				
				rs.beforeFirst();
				
				while (rs.next()) {
					
					   for (int i=0; i<=count; i++) {
						   
						   notes.add(rs.getString(1));
									   
					   }
							
				}
		
				
			} catch (SQLException e) {
				
				e.printStackTrace();
			}
	    
		        stmt.close();
		        rs.close();
			    conn.close();
	    	    	 
	    	 return notes;
	     }
 
	  
	    public static void main (String args[]) throws SQLException
	    
	    {
	    	
	    }
	}

                                  
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Asked On
2009-10-21 at 10:14:46ID24831521
Tags

Java

Topics

New to Java Programming

,

Java Server Pages (JSP)

,

Java Programming Language

Participating Experts
3
Points
500
Comments
17

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Answers

 

by: CEHJPosted on 2009-10-21 at 10:20:03ID: 25626116

 

by: dravidnsrPosted on 2009-10-21 at 10:24:50ID: 25626165

<<<<<<<<<<<   var notes = new Array();
 here ur code is wrong ur creating a notes array here ...
after that u print that !!

so nothing will print ...

put ur resultset list in session or resquest u getting ur jsp

 

by: aman0711Posted on 2009-10-21 at 10:25:34ID: 25626172

Thanks Charles,


                    Is this what I need to do??

Vector<ArrayList<String>> hmNote = new Vector<ArrayList<String>>();
				
				
				rs.last();
				
				count = rs.getRow();
				
				rs.beforeFirst();
				
				while (rs.next()) {
					
					   for (int i=0; i<=count; i++) {
						   
						   notes.add(rs.getString(1));
									   
					   }
						
					  hmNote.add(notes); 
					   
				}

                                              
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by: aman0711Posted on 2009-10-21 at 10:26:44ID: 25626184

@ dravid,

              I am getting the contents on my jsp. Thats not the issue here. I am binding the notes variable with page scope in my Servlet

 

by: dravidnsrPosted on 2009-10-21 at 10:28:21ID: 25626203

oh..
thtas gd yaar...

 

by: CEHJPosted on 2009-10-21 at 10:29:14ID: 25626214

>>    Is this what I need to do??

What you need to do is use the code at the link i posted

http://technojeeves.com/joomla/index.php/free/59-resultset-to-tablemodel

 

by: aman0711Posted on 2009-10-21 at 10:38:05ID: 25626301

Hi charles,

                so in your code, its going with number of columns, I need to go with number of rows. Correct?

 

by: CEHJPosted on 2009-10-21 at 10:43:31ID: 25626349

My code works irrespective of the number of rows and columns. It will work for one column, as in your case. You call the nested list version of my code

 

by: aman0711Posted on 2009-10-21 at 10:52:08ID: 25626443

I will to understand your code.

Not exactly sure, what it is doing :)

 

by: CEHJPosted on 2009-10-21 at 11:43:30ID: 25626969

Well there's another view here:

http://technojeeves.com/joomla/index.php/free/68-resultset-to-nested-list

I would rather hope that a method called 'resultSetToNestedList' would be self-explanatory ;-) What don't you understand?

 

by: objectsPosted on 2009-10-21 at 15:34:16ID: 25629214

you just need this:

                                rs = stmt.executeQuery(sql);                                
                                notes = new ArrayList<String>();
                                while (rs.next()) {
                                                   notes.add(rs.getString(1));
                                           }

Don't go overcomplicating a simple problem with unecessary code. Keep it simple as we discussed :)

 

by: aman0711Posted on 2009-10-21 at 17:59:55ID: 25629927

Thanks Mick :-)

so we dont ever need a for loop to fill in values into an ArrayList?

 

by: objectsPosted on 2009-10-21 at 23:41:24ID: 25631329

no the while loop is all you need.

 

by: CEHJPosted on 2009-10-22 at 01:18:13ID: 25631754

>>so we dont ever need a for loop to fill in values into an ArrayList?

Yes you do. You just happen not to need one in this case as you're only returning one column.

Arranging your code so it breaks if you want to change the query is not a 'simplification', it's just poor planning and if you get into the habit of making such decisions it will lead to code that is easily breakable and hard to maintain.

If you want to write code well you should be seeing the exercise as applying patterns wherever possible.
Using code that works irrespective of the query is the best course unless there are overwhelming reasons to write code that will effectively only work once

 

by: objectsPosted on 2009-10-22 at 01:38:07ID: 25631870

All that code does is add an extra level of indirection for no gain. You don't need it, what I posted above does all you need, and is lot clearer than something returning a table model when what you actually want a list of notes. Its simpler and clearer, win, win :)

> Arranging your code so it breaks if you want to change the query is not a 'simplification'

sorry, but that just doesn't make sense :)

 

by: CEHJPosted on 2009-10-22 at 01:55:59ID: 25631965

>>is lot clearer than something returning a table model

It doesn't return a TableModel - it returns List<List<T>>

 

by: aman0711Posted on 2009-11-02 at 13:28:07ID: 31644072

Thanks folks :)

20120131-EE-VQP-002

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