Comments on: Login application in Java using MVC and MySQL

By: Ravi Bandakkanavar

Ravi Bandakkanavar — Fri, 25 Mar 2022 00:40:18 +0000

In reply to Pranshu Patel. Hi Pranshu, The error is only with the database connection. What version of MySQL are you using? You may need to change the connection parameter accordingly.

By: Pranshu Patel

Pranshu Patel — Mon, 14 Mar 2022 06:53:09 +0000

List of errors I am dealing with even if I have followed same names and structure!!!!!!

Type Exception Report

Message Cannot invoke “java.sql.Connection.createStatement()” because “con” is null

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception

java.lang.NullPointerException: Cannot invoke “java.sql.Connection.createStatement()” because “con” is null
com.mvc.dao.LoginDao.authenticateUser(LoginDao.java:27)
com.mvc.controller.LoginServlet.doPost(LoginServlet.java:35)
javax.servlet.http.HttpServlet.service(HttpServlet.java:681)
javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
Note The full stack trace of the root cause is available in the server logs.

Apache Tomcat/9.0.55

By: Ravi Bandakkanavar

Ravi Bandakkanavar — Thu, 04 Mar 2021 17:55:53 +0000

In reply to Alexandra Geib.

Hi,

You can achieve it by checking whether the session attribute is set. You can refer to the below link for the example.

https://krazytech.com/programs/session-role-based-java-login-example

By: Alexandra Geib

Alexandra Geib — Thu, 04 Mar 2021 15:54:09 +0000

Hello,

Thank you for this. It is very helpful. Quick question. Is there a way that I can check if a user is logged in or not? I have a sign in/register button and once the user logs in, I would like to change that text to their username instead or to put the log out button in its place.

By: Ravi Bandakkanavar

Ravi Bandakkanavar — Mon, 12 Oct 2020 08:27:00 +0000

In reply to simmy. You need to write a logic in script to frame a JSON object and read it in servlet. Altogether a different application.

By: simmy

simmy — Fri, 09 Oct 2020 04:50:24 +0000

Great efforts….can u help me with how to create multiple page after clicking on submit button in login page using json without creating multiple jsp pages. As i am new to JSON. also what is the difference between Dao and DaoImpl class.
need on urgent basis.

By: Ravi Bandakkanavar

Ravi Bandakkanavar — Fri, 25 Sep 2020 05:10:29 +0000

In reply to student. Hi, The business logic is included in DAO file. Go to LoginDao.java class and add the other table details there.

By: student

student — Fri, 25 Sep 2020 03:22:45 +0000

Hi,
how to change code :
one registration form but two separate tables.
thank you

By: Ravi Bandakkanavar

Ravi Bandakkanavar — Fri, 10 Jul 2020 17:45:04 +0000

In reply to nrsffz.

Hi,
I have analyzed the issue. The issue is mainly because of using the higher version of the MySQL server.
The Mysql connection string and driver details need to be updated if you are using MySQL version 5+. If not, the same code will work.

Please find a similar code here. You can refer to the jar file from here. – https://krazytech.com/wp-content/uploads/2020/07/RegistrationMvc.zip

By: nrsffz

nrsffz — Wed, 08 Jul 2020 16:18:04 +0000

Hi, I’m getting an error. I’m already check my LoginServlet but there’s no error.

HTTP Status 404 – Not Found

Type Status Report

Message /LoginMvc/LoginServlet

Description The origin server did not find a current representation for the target resource or is not willing to disclose that one exists.