Vector from bean to servlet?

[Ram Luchman]

I'm getting nullpointer exception when I pass a resultset turned into vector from a bean to a servlet. I can pass the vector from the bean to a JSP page without problems. My code below. The error happens at this point "rs = (Vector)d.getQueryresult();"

package sqlQuery;
import java.sql.*;
import java.util.Vector;
import java.util.Hashtable;
public class QueryBean
{
private String JdbcDrv;
private String JdbcDsn;
private String DBUser;
private String DBPassword;
private String query; 
private Vector v;
private Connection con;
private ResultSet rs;
private Statement st;

public QueryBean()
{
JdbcDrv = "";
JdbcDsn = "";
DBUser = "";
DBPassword = "";
query = "";
con = null;
rs = null;
st = null;
v = null;
}

public void setDBDriver(String dr)
{
JdbcDrv = dr;
}

public void setDBDsn(String ds)
{
JdbcDsn = ds;
}

public void setSQLquery(String sq)
{
query = sq;
}

public Vector getQueryresult() 
{
try 
{

Class.forName(JdbcDrv);
con = DriverManager.getConnection(JdbcDsn, DBUser, DBPassword);

st = con.createStatement();
rs = st.executeQuery(query);

v = new Vector();
ResultSetMetaData meta = rs.getMetaData();
 
 while(rs.next())
{
Hashtable row = new Hashtable();
   for (int x = 1; x <= meta.getColumnCount(); x++)
{
String column = meta.getColumnName(x);
String value = rs.getString(column);
    if (value == null || value == "")
{
    value="";
    }
   row.put(column,value.trim());
  }
    v.add(row);
 }
} 
catch (Exception e) 
{
    e.printStackTrace();
}
finally
{
         try 
         {
         if (rs != null) 
         {rs.close();}
            if (st != null) 
            {st.close();}
            if (con != null) 
            {con.close();}
            }
            catch (SQLException e) 
            {
            e.printStackTrace();
            }
}
v.trimToSize();
return v;
}

}
package baseServlets;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.Vector;
import sqlQuery.QueryBean;

public class Login extends HttpServlet 
{
public void doPost (HttpServletRequest request, HttpServletResponse response) 
  {
  Vector rs = new Vector();
  String drv = getServletContext().getInitParameter("jdbcDriver");
  String dsn = getServletContext().getInitParameter("jdbcDsn");
  String q;
  String userName = request.getParameter("userName");
  String password = request.getParameter("password");
  QueryBean d = new QueryBean();
  
  try
  {
  q = "SELECT * FROM Employees";
  q += "WHERE userID = '" + userName + "' AND password = '" + password + "'";
    
  
  d.setDBDriver(drv);
  d.setDBDsn(dsn);
  d.setSQLquery(q);
  
   rs = (Vector)d.getQueryresult();
   }
   catch (Exception e) 
   {
   log("\n\nError: ", e);
      e.printStackTrace();
       }
       
       try
       {
       if (rs.isEmpty())
       {
       request.getRequestDispatcher("/index.jsp?logfail=1").
            forward(request, response); 
         }
         else
         {       
       request.getRequestDispatcher("/test.jsp").
            forward(request, response); 
         }
          
         }
         catch (Exception e)
         {
         log("\n\nRedirect Error: ", e);
         e.printStackTrace();
         }
         
               
  }
  
  
  public void doGet (HttpServletRequest request, HttpServletResponse response) 
  {
  doGet(request, response);
  }
  
  
} 

[Mike Curwen]

One minor point, you shouldn't need to cast (Vector), because the return type of the method is a Vector.

The other thing is when you are building your query, you don't leave a space between the tablename and the WHERE clause.

If you printed the contents of the String 'q', you'd get "SELECT * FROM EmployeesWHERE userID = etc, etc...

Your try-catch-finally in your bean appears to be good, so I'd expect you would find the SQLException stack trace in your log. the 'return v' is in your finally block, so that should be ok.

What about the stack trace you do see? Can you post it?

[Mike Curwen]

wait, it's not in the finally block.

In the bean class, the line that would throw the exception from a malformed query string is:

rs = st.executeQuery(query);

but only after that do you make the new vector.

v = new Vector();

Then below, when you attempt:

v.trimToSize(); This line should throw a NullPointerException