Java Servlet Form Post issue : getParameters() return null values

Question

i am new here and not native english speaker :). So, i programmed a form that sent simple values via a post method within a java servlet. At first, it worked with request.getParameter(), i don't know what i did, but it doesn't work anymore.

package servlets;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//import services.*;

//import org.json.JSONException;
//import org.json.JSONObject;

public class Authentification extends HttpServlet{

    public void doGet(HttpServletRequest req, HttpServletResponse res) throws  ServletException, IOException {
        res.setContentType("text/html");
        PrintWriter writer = res.getWriter();

        writer.println("<h1>Bienvenue sur notre nouveau site WEB</h1>");
        writer.println("<body>");

        //Form
        writer.println("<form action="+"Authentification"+" method="+"post"+" class="+"form"+">");

        //login
        writer.println("<div class="+">");
        writer.println("<label for="+"login"+">Login:");
        writer.println("<input type="+"text"+" name="+"login"+"/>");
        writer.println("</label>");
        writer.println("</div>");

        //password
        writer.println("<div class="+">");
        writer.println("<label for="+"pwd"+">Password:");
        writer.println("<input type="+"text"+" name="+"pwd"+"/>");
        writer.println("</label>");
        writer.println("</div>");

        //button form
        writer.println("<div class="+"button"+">");
        writer.println("<button type="+"submit"+" name="+"button_connexion"+" value="+"Se_connecter"+">Connexion</button>");
        writer.println("</div>");
        writer.println("</form>");

        //aller sur le lien de l'inscription
        writer.println("<a href="+"/ProjetWeb2020/Inscription"+">T'es nouveau?Par ici l'inscription</a>");
        writer.println("</body>");


    }

    public void doPost(HttpServletRequest req, HttpServletResponse res) throws  ServletException, IOException {
        res.setContentType("text/html");
        PrintWriter writer = res.getWriter();

        String login, pwd;

        login=req.getParameter("Login");
        pwd=req.getParameter("Pwd");

        if(login==null && pwd==null){
            writer.println("<h1>Not good!</h1>");
        }
        //JSONObject obj=services.Authentification.loginUtilisateur(login, pwd);

        writer.println("<h2>login is:"+login+"</h2>");
        writer.println("<h2>pwd is:"+pwd+"</h2>");
    }
}

And the result i don't want no more.

enter image description here

I will aprecciate any answer with great pleasure :)

You have typo in your code change login=req.getParameter("Login"); to login=req.getParameter("login"); and pwd=req.getParameter("Pwd"); to pwd=req.getParameter("pwd"); — Swati
– Swati, Commented Apr 8, 2020 at 16:59
Thank you very much for your quick answer :) but the issue is not about the typo, i noticed it to kumar also. — FerusCom10
– FerusCom10, Commented Apr 8, 2020 at 18:33
check your browser console->inspect-> html (See if correct html is generated also inputs name are same or not ) — Swati
– Swati, Commented Apr 9, 2020 at 9:49
I looked at the html code and here it is: <h1>Bienvenue sur notre nouveau site WEB</h1> <body> <form action=Authentification method=post class=form> <div class=> <label for=login>Login: <input type=text name=login/> </label> </div> <div class=> <label for=pwd>Password: <input type=text name=pwd/> </label> </div> <div class=button> <button type=submit name=button_connexion value=Se_connecter>Connexion</button> </div> </form> <a href=/ProjetWeb2020/Inscription>T'es nouveau?Par ici l'inscription</a> </body> — FerusCom10
– FerusCom10, Commented Apr 9, 2020 at 13:33

FerusCom10 · Accepted Answer · 2020-04-09 14:08:45Z

So, thank you everybody, and especially Swati for the solution. Yes, the issue as a typo thing about "backslash".

I give you the correct code:

package servlets;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//import services.*;

//import org.json.JSONException;
//import org.json.JSONObject;

public class Authentification extends HttpServlet{

    public void doGet(HttpServletRequest req, HttpServletResponse res) throws  ServletException, IOException {
        res.setContentType("text/html");
        PrintWriter writer = res.getWriter();

        writer.println("<h1>Bienvenue sur notre nouveau site WEB</h1>");
        writer.println("<body>");

        //Form
        writer.println("<form action="+"\"Authentification\""+" method="+"\"post\""+" class="+"\"form\""+">");

        //login
        writer.println("<div class=\" \">");
        writer.println("<label for="+"\"login\""+">Login:");
        writer.println("<input type="+"\"text\""+" name="+"\"login\""+"/>");
        writer.println("</label>");
        writer.println("</div>");

        //password
        writer.println("<div class=\" \">");
        writer.println("<label for="+"\"pwd\""+">Password:");
        writer.println("<input type="+"\"text\""+" name="+"\"pwd\""+"/>");
        writer.println("</label>");
        writer.println("</div>");

        //button form
        writer.println("<div class="+"\"button\""+">");
        writer.println("<button type="+"\"submit\""+" name="+"\"button_connexion\""+" value="+"\"Se_connecter\""+">Connexion</button>");
        writer.println("</div>");
        writer.println("</form>");

        //aller sur le lien de l'inscription
        writer.println("<a href="+"/ProjetWeb2020/Inscription"+">T'es nouveau?Par ici l'inscription</a>");
        writer.println("</body>");


    }

    public void doPost(HttpServletRequest req, HttpServletResponse res) throws  ServletException, IOException {
        res.setContentType("text/html");
        PrintWriter writer = res.getWriter();

        String login, pwd;

        login=req.getParameter("login");
        pwd=req.getParameter("pwd");

        if(login==null && pwd==null){
            writer.println("<h1>Not good!</h1>");
        }
        //JSONObject obj=services.Authentification.loginUtilisateur(login, pwd);

        writer.println("<h2>login is:"+login+"</h2>");
        writer.println("<h2>pwd is:"+pwd+"</h2>");
    }
}

And the syntax of the html page:(you can check the ancient html code in my previous comments)

<h1>Bienvenue sur notre nouveau site WEB</h1>
<body>
<form action="Authentification" method="post" class="form">
<div class=" ">
<label for="login">Login:
<input type="text" name="login"/>
</label>
</div>
<div class=" ">
<label for="pwd">Password:
<input type="text" name="pwd"/>
</label>
</div>
<div class="button">
<button type="submit" name="button_connexion" value="Se_connecter">Connexion</button>
</div>
</form>
<a href=/ProjetWeb2020/Inscription>T'es nouveau?Par ici l'inscription</a>
</body>

Moral of the story:be careful with " ", use Backslash in strings for html code!

Kumar Abhinav · Accepted Answer · 2020-04-08 17:07:02Z

0

change the param names while accessing. login=req.getParameter("login"); pwd=req.getParameter("pwd");

it will work.

answered Apr 8, 2020 at 17:07

Kumar Abhinav

11 bronze badge

1 Comment

FerusCom10 Over a year ago

Thank you very much for your quick answer :) I modified the name attribute of each input and didn't modify in the getParameters() to fit the names. But the issue not there, it doesn't work.

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