CODEWITHSUNDEEP
javajspservletsparametersattributes
Jaimin Patel
Jaimin Patel

Reputation: 4637

Can't retrieve data from the Same Servlet using request.getParameter() or request.getAttributes(), tried both get null only

I am sending flag=update to call update method with URL and also send the id of current record which user want to edit the record. Here my problem is I am unable to get parameters (fname, lname, email, pass, cno) values from the edit method. Every time it returns null from update method.

I think something wrong at update method or edit method. Please look into the matter. I want to understand why this problem occurs since I'm trying from last many hours.

I know that I can use request.getAttributes(); instead of request.getParameter(); to get data in the same servlet but let me know if their is any simple way or not? and please help to solve my problem. Thanks in advance.

Registration.html

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Registration Page</title>
</head>
<body>

<form action="Controller1" >

First Name : <input type="text" name="fName"><br/> 
Last Name : <input type="text" name="lName"><br/>
Email : <input type="text" name="eMail"><br/>
Password : <input type="password" name="password"><br/>
Contact No : <input type="text" name="cNo"><br/><br/>

<input type="submit"  value="Register">
<input type="hidden" name="flag" value="register">

 &nbsp;&nbsp;&nbsp;<a href="Controller1?flag=login">Login</a>
</form>

</body>
</html>

Login.html

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Login Page</title>
</head>
<body>

<form action="Controller1">

Email : <input type="text" name="lin_Email" value="insert your registered EmailID"><br/>
Password : <input type="text" name="lin_Pass" value="enter your registered password"><br/>

<input type="submit" value="Login">
<input type="hidden" name="flag" value="loginValidate">

</form>

</body>
</html>

Controller1.java

import java.io.IOException;

import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Controller1
 */
@WebServlet("/Controller1")
public class Controller1 extends HttpServlet {
    private static final long serialVersionUID = 1L;
    int id;
    String fname, lname, email, pass, cno, flag;
    PrintWriter out;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public Controller1() {
        super();
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        flag = request.getParameter("flag");

        if (flag.equals("register")) {
            register(request, response);
        } else if (flag.equals("login")) {
            response.sendRedirect("/JDBC_Registration/Login.html");
        }

        else if (flag.equals("loginValidate")) {
            loginValidate(request, response);
        } else if (flag.equals("view")) {
            try {
                view(request, response);
            } catch (SQLException e) {
                                e.printStackTrace();
            }
        } else if (flag.equals("edit")) {
            try {
                edit(request, response);
            } catch (SQLException e) {

                e.printStackTrace();
            }
        } else if (flag.equals("delete")) {
            delete(request, response);
        }
        else if (flag.equals("update")) {
            try {
                update(request, response);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    private void update(HttpServletRequest request, HttpServletResponse response) throws IOException, SQLException, ServletException {
        response.setContentType("text/html");
        out = response.getWriter();

        id = Integer.parseInt(request.getParameter("id"));
//
//      String fname = request.getParameter("t1");
//      String lname = request.getParameter("t2");
//      String email = request.getParameter("t3");
//      String pass = request.getParameter("t4");
//      String cno = request.getParameter("t5");

        fname = (String) request.getAttribute("t1");
        lname = (String) request.getAttribute("t2");
        email = (String) request.getAttribute("t3");
        pass = (String) request.getAttribute("t4");
        cno = (String) request.getAttribute("t5");
        System.out.println("updated values... "+fname+"  "+lname+" "+email+" "+pass+" "+cno);
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test2","root","root");
            Statement stm = con.createStatement();

            stm.executeUpdate("update registration set FirstName='"+fname+"',LastName='"+lname+"',Email='"+email+"',Password='"+pass+"',ContactNo='"+cno+"' where id='"+id+"'");
            view(request, response);

        } catch (ClassNotFoundException e) {

            e.printStackTrace();
        }
    }

    private void delete(HttpServletRequest request, HttpServletResponse response) throws IOException {
        response.setContentType("text/html");
        out = response.getWriter();
        id = Integer.parseInt(request.getParameter("id"));
        System.out.println("delete record ID....."+id);

        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test2","root","root");
            Statement stm = con.createStatement();

            stm.executeUpdate("delete from registration where id='"+id+"'");
            System.out.println("successfully deleted...record ID : "+id);
            view(request, response);
        }catch (Exception e) {
            System.out.println(e);
        }
    }

    private void edit(HttpServletRequest request, HttpServletResponse response) throws IOException, SQLException {
        response.setContentType("text/html");
        out = response.getWriter();
        id = Integer.parseInt(request.getParameter("id"));
        System.out.println(""+id);

        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test2","root","root");
            Statement stm = con.createStatement();

            ResultSet rs = stm.executeQuery("select * from registration where id='"+id+"'");

            out.println("<form action='Controller1'><table border=2>");
            out.println(
                    "<tr><td>ID</td><td>FirstName</td><td>LastName</td><td>Email</td><td>Password</td><td>ContactNo</td><td>Action</td></tr>");
            while (rs.next()) {
                out.println("<tr><td>" + rs.getString(1) + "</td><td><input type='text' name='t1' value=" + rs.getString(2) + "></td><td><input type='text' name='t2' value=" + rs.getString(3) + "></td><td><input type='text' name='t3' value=" + rs.getString(4) + "></td><td><input type='text' name='t4' value=" + rs.getString(5) + "></td><td><input type='text' name='t5' value=" + rs.getString(6) + "></td><td>&nbsp;&nbsp;<a href=Controller1?flag=update&id=" + rs.getString(1)
                        + ">Update</a>&nbsp;&nbsp;</td></tr>");
            }

            out.println("</table></form>");

        } catch (ClassNotFoundException e) {

            e.printStackTrace();
        }
    }

    private void view(HttpServletRequest request, HttpServletResponse response)
            throws SQLException, IOException, ServletException {
        response.setContentType("text/html");
        out = response.getWriter();
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test2", "root", "root");
            Statement stmt = con.createStatement();

            // RequestDispatcher rd =
            // request.getRequestDispatcher("Welcome.html");
            // rd.include(request, response);

            ResultSet rs = stmt.executeQuery("select * from registration");
            out.println("<form><table border=2>");
            out.println(
                    "<tr><td>ID</td><td>FirstName</td><td>LastName</td><td>Email</td><td>Password</td><td>ContactNo</td><td>Action</td></tr>");
            while (rs.next()) {
                out.println("<tr><td>" + rs.getString(1) + "</td><td>" + rs.getString(2) + "</td><td>" + rs.getString(3)
                        + "</td><td>" + rs.getString(4) + "</td><td>" + rs.getString(5) + "</td><td>" + rs.getString(6)
                        + "</td><td>&nbsp;&nbsp;<a href=Controller1?flag=edit&id=" + rs.getInt(1)
                        + ">Edit</a>&nbsp;&nbsp;&nbsp;&nbsp; <a href=Controller1?flag=delete&id=" + rs.getInt(1)
                        + ">Delete</a>&nbsp;&nbsp;</td></tr>");
            }

            out.println("</table></form>");

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }

    }

    private void loginValidate(HttpServletRequest request, HttpServletResponse response) throws IOException {

        response.setContentType("text/html");
        out = response.getWriter();

        try {
            email = request.getParameter("lin_Email");
            pass = request.getParameter("lin_Pass");
            System.out.println("" + email + pass);

            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test2", "root", "root");
            Statement stmt = con.createStatement();

            ResultSet rs = stmt
                    .executeQuery("select * from registration where Email='" + email + "'and Password='" + pass + "'");

            if (!rs.next()) {
                out.println("<h4 style='color:red'>Please Enter correct Email ID & Password...sq</h4><br/><br/>");
                // response.sendRedirect("/JDBC_Registration/Login.html");
                RequestDispatcher rd = request.getRequestDispatcher("Login.html");
                rd.include(request, response);
            } else {
                // System.out.println("else if called....");
                out.println("<h1>Welcome User :</h1><h3>" + rs.getString(2)
                        + "</h3>&nbsp;&nbsp;&nbsp;<a href=Controller1?flag=view>view</a>");
                RequestDispatcher rd = request.getRequestDispatcher("Welcome.html");
                rd.include(request, response);
            }
        } catch (Exception e) {
            System.out.println(e);
        }
    }

    private void register(HttpServletRequest request, HttpServletResponse response) throws IOException {

        response.setContentType("text/html");
        out = response.getWriter();

        try {
            fname = request.getParameter("fName");
            lname = request.getParameter("lName");
            email = request.getParameter("eMail");
            pass = request.getParameter("password");
            cno = request.getParameter("cNo");

            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test2", "root", "root");
            Statement stmt = con.createStatement();

            stmt.executeUpdate("insert into registration(FirstName,LastName,Email,Password,ContactNo) values('" + fname
                    + "','" + lname + "','" + email + "','" + pass + "','" + cno + "')");
            System.out.println(" INSERT  : : : " + fname + " " + lname + " " + email + " " + pass + " " + cno);

            response.sendRedirect("/JDBC_Registration/Login.html");

            // view(request, response);
        } catch (Exception e) {
            System.out.println(e);
        }
    }
}

Upvotes: 4

Views: 1170

Answers (2)

Jaimin Patel
Jaimin Patel

Reputation: 4637

it worked for me when i put submit button instead of URL to call update method. 

<input type='submit'>
<input type='hidden' name='flag' value='update'>
<input type='hidden' name='id' value='"+id+"'>

what happened here, Hyperlink value doesn't append with the remaining parameters t1,t2,t3,t4 & t5. By putting Submit button it takes all the parameter as consider as by default get() method.

Upvotes: 4

Alan Pallath
Alan Pallath

Reputation: 99

You have used a form in your jsp page. By default, it goes to the overridden doGet method. Here the function you've used is update(), So, try calling the getAttributes in the doGet method and pass it over to any other function of your choice.

Upvotes: 0

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