salut , j'essai de modifier les donné d'une table, voila le code:
import java.awt.TextField;
import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;


public class First_serv2 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException
{
Connection cnt=null;
Statement st=null,st1=null;
PreparedStatement pst=null;
ResultSet rst=null;



response.setContentType("text/html");
PrintWriter out = response.getWriter();
BufferedReader lineReader = new BufferedReader(new InputStreamReader(System.in));

out.println("<html>");
out.println("<head>");
out.println("<title>Multiplication</title>");
out.println("</head>");
out.println("<body>");

String var;
var=request.getParameter("txt");
out.print(var);



try
{ String url = "jdbc:odbc:db1";
String driver = "sun.jdbc.odbc.JdbcOdbcDriver";
Class.forName(driver).newInstance();
cnt = DriverManager.getConnection(url, "", "");
st=cnt.createStatement();
pst=cnt.prepareStatement("select * from etudiant where num=?");
pst.setString(1,var);
rst=pst.executeQuery() ;

while(rst.next())
{
out.print("<form name=frm3 method='get' action='First_serv2'>");

out.print("numéro etudiant :<input type='text' name='numtxt' value="+rst.getInt(1)+">");
out.print("<br>");
out.print("cne etudiant :<input type=text name='cnetxt' value="+rst.getInt(2)+">");
out.print("<br>");
out.print("nom etudiant :<input type=text name='nomtxt' value="+rst.getString(3)+">");
out.print("<br>");
out.print("prenom etudiant :<input type=text name='prenomtxt' value="+rst.getString(4)+">");



out.print(" <input type='submit' name='btmodif' value='modifier'>");
out.print("</form>");

}
String numtxt;
numtxt=request.getParameter("numtxt");
String cnetxt;
cnetxt=request.getParameter("cnetxt");
String nomtxt;
nomtxt=request.getParameter("nomtxt");
String prenomtxt;
prenomtxt=request.getParameter("prenomtxt");

pst = cnt.prepareStatement("UPDATE etudiant SET cne = ? " + "and nom= ? " + "and prenom= ? " + "WHERE num= ? ");
pst.setString(1,cnetxt);

pst.setString(2,nomtxt);

pst.setString(3,prenomtxt);

pst.setString(4,numtxt);

pst.execute();

cnt.close();





}
catch(Exception e)
{
out.print("Error: " + e);
}


out.print("");
out.print("");
out.print("");
out.println("</body>");
out.println("</html>");
}
}


lorsque je click qur le bouton modifier , rien ne m'arache,et pourtant il ne m'affiche pas un message d'erreur
merci pr votre aide.