Evening Servlet with session

EveningServlet.java

package com.pch;


import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.servlet.http.HttpSession;

import java.io.IOException;

@WebServlet("/evening")
public class EveningServlet extends HttpServlet {

    private static final String greeting = "Good evening, %s!";

    @Override
    protected void doGet(HttpServletRequest req,
                         HttpServletResponse resp) throws ServletException, IOException {
        HttpSession session = req.getSession();
        String nameFromSession = (String) session.getAttribute("name");
        String name = "Buddy";
        var parameterMap = req.getParameterMap();
        var queryParamName = parameterMap.get("name");

        if (queryParamName != null && queryParamName[0] != null) {
            name = queryParamName[0];
            session.setAttribute("name", name);
        } else if (nameFromSession != null) {
            name = nameFromSession;
        }

        var writer = resp.getWriter();

        writer.println(String.format(greeting, name));
        writer.flush();
    }
}