Validation Required Before Loading jsp

I have one scenario where I want to do some validation before my welcome.jsp page get loaded. Actually the validation is like I have a user id (using request.getRemoteUser) which I want to check in my Db whether it is already there or not. If yes, then I want to redirect it into another page say login.jsp. if not, it will redirect to my welcome.jsp. I have declare one servlet (CheckUser.java) where I am calling doPost from the doGet and also included the same servlet in my welcome.jsp so that before loading it doGet will invoke.

**CheckUser.java**

package DBResource;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CheckUser extends DBConnection {
        String page="ListProjects.jsp";
        public Connection conn= null;
        // This Happens Once and is Reused
@Override
public void init(ServletConfig config) throws ServletException
   {
       super.init(config);                       
   }

public boolean SearchUser(String Usrid)  throws SQLException{
   try{

        // Establishing connection using data source
       conn=ds.getConnection();

       PreparedStatement stmt=conn.prepareStatement("select * from OSS_USER where USER_EMAIL='"+Usrid+"'");

                ResultSet rs = stmt.executeQuery();

                boolean hasResult = rs.next();
                return hasResult;

   }

   catch (Exception e){
        e.printStackTrace();
        return false;
    }
   finally {
        if (conn != null) conn.close();
    }

}


@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    System.out.println("on CheckUser doGet...........");
    doPost(request,response);

}


@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {


            System.out.println("on CheckUser doPost..........");
            //String Usrid= request.getRemoteUser();
            String Usrid= "abc@tr.com";

            contextPath = request.getContextPath();
            page = "/ListProjects.jsp";


    try {
        boolean susr =  SearchUser(Usrid);
        if (susr==true)
        {
            response.sendRedirect(contextPath + "/ListProjects.jsp");   

        } 
    } catch (SQLException ex) {
        Logger.getLogger(DBConnection.class.getName()).log(Level.SEVERE, null, ex);
    }
    finally {
        if (conn != null) try {
            conn.close();
        } catch (SQLException ex) {
            Logger.getLogger(DBConnection.class.getName()).log(Level.SEVERE, null, ex);
        }
    }


}

/**
 * Returns a short description of the servlet.
 *
 * @return a String containing servlet description
 */
@Override
public String getServletInfo() {
    return "Short description";
}// </editor-fold>

}

Welcome.jsp

<body>

    <jsp:include page="/CheckUser" flush="true" />

Solution

This issue get Resolved using beans & scriptlet. in the Jsp page i have import my java class(StoreUsrDetails) and declare a jsp use bean (storeusr).

In jsp page

<%@page import="com.thomsonreuters.alpaca.StoreUsrDetails" %>
<jsp:useBean id="storeusr" class="com.thomsonreuters.alpaca.StoreUsrDetails" scope="request" />

using the bean i call a method inside my java method (validateUser) which returns wheather the user details is present in the database or not. after that i have written a scriplet code at the start of my jsp body. And based on the retun value of validateUser method i redirect them to another page.

Jsp Body

<body>
    <% 

           if(storeusr.validateUser(request.getRemoteUser()))  
          response.sendRedirect("ListProjects.jsp");   


    %>