How to delete the row from the Database by using while loop in servlet

Anjaneyulu Mannam

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Posts: 5

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posted 14 years ago

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Dear Sir/Madam,

I am trying to delete the one user data in the Oracle SQL server database by using Servlet program (Tomcat server).

In Database table have 6 users details are there.

Table name is "JDUSER" and columns are USERS (Char), PASS (Varchar2) and CODE (Varchar2). I am trying to delete 4th user details.

While loop is not terminate, in while loop why If condition not working it checking until end of the table and gives else black statement. So what is my mistake and please give the solution to me.

My HTML code is:

My Database table is:

My JavaServlet Program is:

import java.lang.*;
import java.io.*;
import java.sql.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class JdbcDeleteServlet extends HttpServlet
{    
       String dbn,dbp,dbco;
       String un,up,uco;
       boolean flag=false;
       public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException
       {
          try 
           {
               response.setContentType("text/html;charset=UTF-8");
               PrintWriter out = response.getWriter();
               response.setContentType("text/html");  
               un=request.getParameter("uname");
               up=request.getParameter("pwd"); 
               uco=request.getParameter("code"); 
              Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); 
              Connection c=DriverManager.getConnection("jdbc:odbc:hari","raman","raman");
              Statement s=c.createStatement();
              s.execute("select *from jduser");   
              ResultSet rs=s.getResultSet();   
              while(rs.next()) 
               {
                    dbn=rs.getString("users");
                    dbp=rs.getString("pass");
                    dbco=rs.getString("code"); 
                    if(un.equals(dbn)&&up.equals(dbp)&&uco.equals(dbco))          // another formate  if((un==dbn)&&(up==dbp)&&(uco==dbco))
                     {
                         s.executeUpdate("delete jduser where users='"+un+"'");
                         flag=true;
                          break; 
                   } 
             }  
            if(flag==true)
                  out.println("<font color=green>"+dbn+" user Data deleted successfully");
             else 
               out.println("<font color=red>Sorry "+un+" user data is Not Available");
            s.close();
            c.close(); 
           out.close(); 
       } 
       catch(IOException e)
        { 
           System.out.println(e.getMessage());
        }
        catch(SQLException e)
        { 
           System.out.println(e.getMessage());
        } 
       catch(ClassNotFoundException e)
        { 
           System.out.println(e.getMessage());
        }
    }
}

So finally where is my mistake and in while loop If condition true even though if loop not working.
i am given 4th usre details in HTML page. Please give me solution.

Mail ID : [email protected]

Krishna Madhava

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Posts: 11

posted 14 years ago

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Hi,

please check your delete query.

the correct syntax is delete from table where fieldname='value';

once query is modified, hope it will delete the row from the Database

thanks.

ramakrishna rayudu

Ranch Hand

Posts: 57

posted 14 years ago

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Hi..

As per the Good Guidelines All ways You Should Not write any DataBase Related Code in your Servlet.
follow this...
All way The Request Should received By Servelt And it need to Call Any Back end Java Classes Normally Called As Beans(Spring Beans/EJB Beans).
and get The Data from the Beans need to Forward Any jsp page for View Purpose

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