ProjectApplicationsServlet.java

package controller;

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;

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;

@WebServlet("/ProjectApplicationsServlet")
public class ProjectApplicationsServlet extends HttpServlet {

    protected void doPost(
        HttpServletRequest request,
        HttpServletResponse response)
        throws ServletException, IOException {

        HttpSession session = request.getSession(false);

        if (session == null ||
            session.getAttribute("userId") == null) {

            response.sendRedirect("index.jsp");
            return;
        }

        int ownerId =
            (Integer) session.getAttribute("userId");

        String action = request.getParameter("action");

        int requestId =
            Integer.parseInt(
                request.getParameter("request_id")
            );

        try {

            Class.forName("com.mysql.cj.jdbc.Driver");

            Connection conn =
                DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/devconnect_db",
                    "root",
                    "Harsh@@@123"
                );

            String sql;

            if ("approve".equals(action)) {

                sql =
                    "UPDATE project_requests r " +
                    "JOIN projects p ON r.project_id=p.id " +
                    "SET r.status='APPROVED' " +
                    "WHERE r.id=? AND p.posted_by=?";

            } else if ("reject".equals(action)) {

                sql =
                    "UPDATE project_requests r " +
                    "JOIN projects p ON r.project_id=p.id " +
                    "SET r.status='REJECTED' " +
                    "WHERE r.id=? AND p.posted_by=?";

            } else {

                response.sendError(400);
                return;
            }

            PreparedStatement ps =
                conn.prepareStatement(sql);

            ps.setInt(1, requestId);
            ps.setInt(2, ownerId);

            ps.executeUpdate();

            ps.close();
            conn.close();

            response.sendRedirect("my_projects.jsp");

        } catch(Exception e) {

            e.printStackTrace();
            response.sendError(500, e.getMessage());
        }
    }
}