1. Import web_mvc_hibernate_template

• Steps:

  • Import the project as an existing Maven project in your IDE (e.g., Eclipse).

    • File → Import → Maven → Existing Maven Project → Select web_mvc_hibernate_template → Finish.

  • Update the database settings in hibernate.cfg.xml:

    <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/your_db</property>
    <property name="hibernate.connection.username">your_username</property>
    <property name="hibernate.connection.password">your_password</property>
    
    

  • Right-click the project → Maven → Update Project → Check "Force Update" → OK.

  • If needed, run Maven goals:

    mvn clean compile
    
    

  • Ensure dependencies (Hibernate, MySQL connector, JSTL) are in pom.xml.

2. Servlet Context Listener

• Purpose: Initializes and destroys the Hibernate SessionFactory.

• Implementation (HibernateServletContextListener.java):

  import jakarta.servlet.ServletContextEvent;
  import jakarta.servlet.ServletContextListener;
  import jakarta.servlet.annotation.WebListener;
  
  @WebListener
  public class HibernateServletContextListener implements ServletContextListener {
      @Override
      public void contextInitialized(ServletContextEvent sce) {
          HibernateUtils.getSessionFactory(); // Builds SessionFactory
          sce.getServletContext().log("Hibernate SessionFactory initialized");
      }
  
      @Override
      public void contextDestroyed(ServletContextEvent sce) {
          HibernateUtils.shutdown(); // Closes SessionFactory, cleans up DBCP
          sce.getServletContext().log("Hibernate SessionFactory closed");
      }
  }
  
  

• Explanation:

  • contextInitialized: Called when the application starts, builds the SessionFactory.
  • contextDestroyed: Called when the application shuts down, closes the SessionFactory and cleans up the database connection pool (DBCP).

3. Create FrontController Servlet

• Purpose: Centralized request handling and routing for all user-related operations.

• Implementation (FrontController.java):

  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 java.io.IOException;
  import java.time.LocalDate;
  import java.util.List;
  
  @WebServlet(value = "/*", loadOnStartup = 1)
  public class FrontController extends HttpServlet {
      private UserDAO userDAO;
  
      @Override
      public void init() throws ServletException {
          userDAO = new UserDAOImpl(); // Initialize DAO
      }
  
      @Override
      protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
          String path = req.getPathInfo() == null ? "/" : req.getPathInfo();
          switch (path) {
              case "/":
                  listUsers(req, resp);
                  break;
              case "/update_form":
                  showUpdateForm(req, resp);
                  break;
              case "/delete":
                  deleteUser(req, resp);
                  break;
              case "/add_user_form":
                  showAddUserForm(req, resp);
                  break;
              default:
                  resp.sendError(HttpServletResponse.SC_NOT_FOUND, "Invalid path");
          }
      }
  
      @Override
      protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
          String path = req.getPathInfo();
          if ("/insert".equals(path)) {
              insertUser(req, resp);
          } else if ("/update".equals(path)) {
              updateUser(req, resp);
          } else {
              doGet(req, resp); // Delegate to doGet for other cases
          }
      }
  
      private void listUsers(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
          List<User> users = userDAO.getAllUsers();
          req.setAttribute("user_list", users);
          req.getRequestDispatcher("/WEB-INF/views/list.jsp").forward(req, resp);
      }
  
      private void showUpdateForm(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
          Long id = Long.parseLong(req.getParameter("id"));
          User user = userDAO.getUserById(id);
          if (user != null) {
              req.setAttribute("user_details", user);
              req.getRequestDispatcher("/WEB-INF/views/update_form.jsp").forward(req, resp);
          } else {
              resp.sendError(HttpServletResponse.SC_NOT_FOUND, "User not found");
          }
      }
  
      private void deleteUser(HttpServletRequest req, HttpServletResponse resp) throws IOException {
          Long id = Long.parseLong(req.getParameter("id"));
          String result = userDAO.deleteUser(id);
          resp.sendRedirect(req.getContextPath() + "/"); // Redirect to list
      }
  
      private void showAddUserForm(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
          req.getRequestDispatcher("/WEB-INF/views/add_user.jsp").forward(req, resp);
      }
  
      private void insertUser(HttpServletRequest req, HttpServletResponse resp) throws IOException {
          User user = new User();
          user.setName(req.getParameter("name"));
          user.setPassword(req.getParameter("pass"));
          user.setRole(req.getParameter("role"));
          user.setDob(LocalDate.parse(req.getParameter("dob")));
          String result = userDAO.addUser(user);
          resp.sendRedirect(req.getContextPath() + "/"); // Redirect to list
      }
  
      private void updateUser(HttpServletRequest req, HttpServletResponse resp) throws IOException {
          Long id = Long.parseLong(req.getParameter("id"));
          User user = userDAO.getUserById(id);
          if (user != null) {
              user.setName(req.getParameter("name"));
              user.setPassword(req.getParameter("pass"));
              user.setRole(req.getParameter("role"));
              user.setDob(LocalDate.parse(req.getParameter("dob")));
              String result = userDAO.changePassword(id, user.getPassword()); // Assuming merge-like behavior
              resp.sendRedirect(req.getContextPath() + "/"); // Redirect to list
          } else {
              resp.sendError(HttpServletResponse.SC_NOT_FOUND, "User not found");
          }
      }
  }
  
  

• Explanation:

  • Annotation: @WebServlet(value = "/*", loadOnStartup = 1) intercepts all requests and initializes the servlet eagerly.
  • Routing: doGet handles GET requests, doPost handles POST requests (e.g., form submissions).
  • Paths:
    • /: Lists all users.
    • /update_form: Shows update form for a user.
    • /delete: Deletes a user.
    • /add_user_form: Shows add user form.
    • /insert: Handles new user creation (POST).
    • /update: Handles user updates (POST).
  • Redirect vs Forward: Redirect (resp.sendRedirect) for POST operations to refresh the view; Forward (req.getRequestDispatcher) for rendering JSPs.

4. View Layer (JSPs)

• Design Practice:
  • Store JSPs under /WEB-INF/views/ to prevent direct access.
  • Use JSTL for iteration and data binding instead of scriptlets.
• JSTL Setup:

  1. Copy JSTL JARs (jstl-1.2.jar) to <tomcat>/lib.

  2. Add JSTL dependency in pom.xml:

     <dependency>
         <groupId>javax.servlet</groupId>
         <artifactId>jstl</artifactId>
         <version>1.2</version>
     </dependency>
     
     

5. list.jsp

• Purpose: Displays a table of users with links for update and delete.