java.sql.SQLException: Operation not allowed after ResultSet closed

java.sql.SQLException: Operation not allowed after ResultSet closed .

I thought that this exception worth posting here, since when i struck up with this exception, i tried to search in many of the java forums, but they haven't provide me the alternative solution to this problem. Anyhow, as an introduction to this problem, i am writing an application in which the a user will be logged in to the system with his user-id and is able to pick up one of the roles assigned to him at a particular time. So i thought that without writing the two seperate servlet programs i ended this within one program using both doGet() and doPost() methods. But when i required to show the roles available to the particular user, i required to connect to the database again { previously i connected to check the user credentials, and i am still in that loop}, i had created one more resultSet and inserted a stament like:
rs1=stmt.executeUpdate("select roleName from userroles where user=' "+user+" ' ");
compiled successfully, but when i tried to run it, i gives me exception that "Operation not allowed after ResultSet closed", where i am trying to use the same statement connection. I later thought that i got this exception because of lack knowledge of JDBC drivers. In any application we have to connect to only one Statement to the ResultSet and if we want to connect again we need to use PreparedStatement Object, instead of the Statement Object. And to have more connections we need to instantiate CallableStatement Objects. This resolves me the problem of connecting to the database with as many statements as required at the same time.
So i used the following code fragment:
..............
Statement stmt=conn.createStatement();
ResultSet rs=stmt.executeUpdate("select userName, password from users where userName=' "+user+" ' ");
PreparedStatement pstmt=conn.prepareStatement("select roleName from userroles where userName=' "+user+" ' ");
ResultSet rs1=pstmt.executeQeury();
...
while(rs.next()){
.....
while(rs1.next()) {
....
}
}
.........
This way of programming solves me the problem. Though i am trying to look at the other alternatives if any.