2024.5.11 Saturday
Continued from 【WEEK11】 【DAY5】Employee Management System Part 6【English Version】

10.8. Delete and 404 Handling

10.8.1. Modify list.html

<a class="btn btn-sm btn-danger" th:href="@{/delemp/{id}(id=${emp.getId})}">Delete</a><!--@{/delemp/}+${emp.getId()} can also be written this way-->

10.8.2. Modify EmployeeController.java

package com.P14.controller;

import com.P14.dao.DepartmentDao;
import com.P14.dao.EmployeeDao;
import com.P14.pojo.Department;
import com.P14.pojo.Employee;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;

import java.util.Collection;

@Controller
public class EmployeeController {
    // Query all employees
    @Autowired
    EmployeeDao employeeDao;
    @Autowired  // Autowire
    DepartmentDao departmentDao;

    @RequestMapping("/emps")    // Whenever dashboard.html requests th:href="@{emps}" (line 89), it will be redirected to @RequestMapping("/emps")
    public String list(Model model){    // Then it will query all employees, and modify: how to display them on the front-end page
        Collection<Employee> employees = employeeDao.getAll();
        model.addAttribute("emps",employees);
        return "emp/list";
    }

    @GetMapping("/emp") // Get request for redirection
    public String toAddpage(Model model){
        // Retrieve information of all departments
        Collection<Department> departments = departmentDao.getDepartment();
        model.addAttribute("departments",departments);
        return "emp/add";
    }

    @PostMapping("/emp")
    public String addEmp(Employee employee){
        // Adding operation forward
        System.out.println("save=>"+employee);
        employeeDao.save(employee); // Call the underlying business method to save employee information
        return "redirect:/emps";    // After clicking "Add" on the "Add Employee" page, redirect to the "Employee Management" page
    }


    // Go to the employee update page -> should be able to retrieve the original data
    @GetMapping("/emp/{id}")
    public String toUpdateEmp(@PathVariable("id") Integer id,Model model){
        Employee employee = employeeDao.getEmployeeById(id);
        model.addAttribute("emp",employee);

        // Retrieve information of all departments
        Collection<Department> departments = departmentDao.getDepartment();
        model.addAttribute("departments",departments);

        return "emp/update";
    }

    @PostMapping("/updateEmp")
    public String updateEmp(Employee employee){
        employeeDao.save(employee);
        return "redirect:/emps";
    }

    // Delete employee
    @GetMapping("/delemp/{id}")
    public String deleteEmp(@PathVariable("id") int id){
        employeeDao.delete(id);
        return "redirect:/emps";
    }

}

10.8.3. Restart

10.8.4. 404 Page Handling

Create error folder

10.8.4.1. Move the 404.html file into it

To prevent loss of page style, add two slashes //

10.8.4.2. Restart and Run

Enter any URL that does not correspond to a page

If the 404.html is not placed in the error folder, the error page will be displayed with the default browser style:

10.8.5. Logout

10.8.5.1. Modify commons.html

<a class="nav-link" th:href="@{/user/logout}">Sign out</a>

10.8.5.2. Modify LoginController.java

package com.P14.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.thymeleaf.util.StringUtils;

import javax.servlet.http.HttpSession;

@Controller
public class LoginController {

    @RequestMapping("/user/login")
    public String login(@RequestParam("username") String username,
                       @RequestParam("password") String password,
                       Model model,
                       HttpSession session){
        // Business logic
        if (!StringUtils.isEmpty(username) && "123456".equals(password)){
            session.setAttribute("loginUser",username);
            // Login successful, redirect to /main (already set to redirect to dashboard.html in MyMvcConfig)
            return "redirect:/main.html";
        }else {
            // Failed login message
            model.addAttribute("msg","Invalid username or password");
            return "index";
        }
    }

    // Logout
    @RequestMapping("/user/logout")
    public String logout(HttpSession session){
        session.invalidate();
        return "redirect:/index.html";
    }
}

10.8.5.3. Restart

• After login, not logging out -> even if returned to the login page -> can directly access desired URL by entering it again
  
  Return to the login page:
  
  At this point, desired URLs can be accessed directly by entering them:
  For example: http://localhost:8080/emps
  

For example: http://localhost:8080/main.html

• After login, then logout -> back to the login page -> must login again to access desired URL
  
  Return to the login page:
  
  Attempting to access main.html by modifying the URL fails, indicating successful user logout.
  

10.9. Summary

10.9.1. How to Build a Website

10.9.1.1. Frontend: Design the appearance using layui
10.9.1.2. Database design (Database design challenges)
10.9.1.3. Make the frontend self-executing and independent
10.9.1.4. How to connect data interfaces: JSON, objects, all in one!
10.9.1.5. Frontend-backend integration testing

10.9.2. Templates

10.9.3. Have a set of familiar backend templates: Essential for work! Recommended to use: x-admin
10.9.4. Frontend pages: At least be able to combine a website page using frontend frameworks

• index
• about
• blog
• post
• user

10.9.5. Make this website able to run independently!