Confused about the warning "Cannot resolve variable"

Question

In login.java I am using req.setAttribute("username", req.getParameter("username")); and in welcome.jsp I am using Hello ${username} but Intellij gives me the warning:

Cannot resolve variable 'username'

The variable works. Why do I get this warning?

login.java

package ch.yourclick.zt;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/login")
public class Login extends HttpServlet {
    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setAttribute("username", req.getParameter("username"));
        req.setAttribute("password", req.getParameter("password"));
        req.getRequestDispatcher("/welcome.jsp").forward(req, resp);
    }
}

`Cannot resolve variable 'username'` means username is not declared — Akash Jain, May 04 '19 at 21:03
intelJ might not have imported the dependency's at that moment but your compiler will not be effected as the classes are imported during runtime , try cleaning your project it might help. — Akash Jain, May 04 '19 at 21:21
https://stackoverflow.com/questions/5905896/intellij-inspection-gives-cannot-resolve-symbol-but-still-compiles-code here is a similar question — Akash Jain, May 04 '19 at 21:26

Hien Nguyen · Answer 1 · 2019-05-05T11:01:24.690

1

May be your login.java you use sendRedirect to welcome.jsp page and it lost request scope variable.

response.sendRedirect("welcome.jsp");

In login.java you need change to this to keep username variable

RequestDispatcher requestDispatcher = request.getRequestDispatcher("welcome.jsp");
requestDispatcher.forward(request, response);

For prevent warning you can update setting for Intellij > Setting > Code Inspection

https://www.jetbrains.com/help/idea/code-inspection.html

edited May 05 '19 at 11:01

answered May 05 '19 at 04:30

Hien Nguyen

24,551
7
52
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Thanks, I did the same but I still get the same warning. – Ray May 05 '19 at 10:16
Where did you set attribute username ? You need add req.setAttribute before forward in doPost – Hien Nguyen May 05 '19 at 10:19
I have updated my question and posted the whole code. – Ray May 05 '19 at 10:38
In your code you only set attribute for password, need set attribute for username too – Hien Nguyen May 05 '19 at 10:39
Yeah sorry, my bad. Actually it has both, username and password. I have updated the code but the warning stays the same. – Ray May 05 '19 at 10:44
In your browser is it displayed username? – Hien Nguyen May 05 '19 at 10:48
Yes, it is displayed. – Ray May 05 '19 at 10:49
you can update setting at https://www.jetbrains.com/help/idea/code-inspection.html and https://www.jetbrains.com/help/idea/thymeleaf.html – Hien Nguyen May 05 '19 at 11:00
You can update setting for code inspection like updated answer – Hien Nguyen May 05 '19 at 11:02
Thanks for that info. I could uncheck `EL Validation in JSP`. Then I wouldn't get any warnings at all. For instance, if I use `${something}` and the variable `something` really doesn't exist, I won't get any warnings. – Ray May 05 '19 at 11:46

score 1 · Accepted Answer · answered May 13 '19 at 15:52

1

You have 2 options:

Option 1

<% String username = (String) request.getAttribute("username"); %>
<%= username %>

Option 2

${requestScope.username}

answered May 13 '19 at 15:52

Reza Saadati

5,018
4
27
64

Confused about the warning "Cannot resolve variable"

2 Answers2