Whats wrong with this code

[raghu dubey]

Hi All,

Below is the code for a Model class that gets called from my controller servlet. The problem is that the List<List<String>> object does not get populated with the column details. I just get a List of lists where each list is not containing the row data and is just blank. The for loop at the end just prints the blank data. Please help:

Using tomcat 5.5 and JDK 5.

====

import java.util.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
 
public class ConfigModel {
 
Connection con;
 
String connectionURL = "jdbc:jtds:sqlserver://localhost:1433/BSM";
 
/**
 * Using initilizer block to load JTDS JDBC driver and open a connection
 * This connection is only closed when finalize method runs at the end.
 */
{
 
try {
Class.forName("net.sourceforge.jtds.jdbc.Driver");
con = DriverManager.getConnection(connectionURL, "bsm", "raghu123");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
 
}
 
/**
 * This method returns a List of List of Strings that are obtained from the
 * database of the selected Configuration area table from the BSM database.
 * 
 * @param acntCode -
 *            Three digit account code.
 * @param configAreaTable -
 *            The name of the BSM table from whick to pull data
 * 
 * @return returns a java.util.List of List objects. Each List object
 *         contains one row of the selected table.
 */
 
public List<List<String>> getTableData(String acntCode,
String configAreaTable) {


List<List<String>> table = new ArrayList<List<String>>();
List<String> tableRow = new ArrayList<String>();


String query = "SELECT * FROM " + configAreaTable
+ " where Account_Name = '" + acntCode + "'";
System.out.println(query);
try {
Statement stmt = con.createStatement();
ResultSet result = stmt.executeQuery(query);
 
ResultSetMetaData mtdt = result.getMetaData();
int count = mtdt.getColumnCount();

/**This for loop adds the column names to the first row
 * of the list that is passed to the controller so that the final 
 * JSP can actually display the column names as well
 * */
for (int j = 1; j != count; j++) {
 
tableRow.add(mtdt.getColumnName(j));
}
table.add(tableRow);
tableRow.clear();

/**This piece of code loops through each column of the result set, row by row
 * and creates a list of List of String objects. At the end of loop, 
 * we are clearing the list that contains single row talbe data
 * to prepare it for storing the next row at the next iteration*/
while (result.next()) {
 
for (int j = 1; j != count; j++) {
 
//System.out.print(result.getString(j) + "");
tableRow.add(result.getString(j));
}
table.add(tableRow);
//System.out.println();
tableRow.clear();
}

[B]for(List<String> s: table){
for (String s1: s){

System.out.println(s+"  ");
}
System.out.println();
}[/B]
 
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
 
return table;
}
 
}

===========

[ Edited to use code tags - Paul Sturrock ]
[ October 06, 2008: Message edited by: Paul Sturrock ]

[David O'Meara]

You're reusing the same List instance each time and wiping it clean.
You need to create a new instance each time otherwise everyone will end up with a reference to the same List<String>, which will be empty.

[raghu dubey]

Thanks David