AuthorizationController


package adil.java.schoolmaven.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class  AuthorizationController{

    // If user will be successfully authenticated he/she will be taken to the login secure page.
    @RequestMapping(value="/admin", method = RequestMethod.GET)
    public ModelAndView adminPage() {

        ModelAndView m = new ModelAndView();
        m.addObject("title", "Вы успешно вошли");
        m.addObject("message", "Основная");
        m.setViewName("admin");

        return m;
    }

    // Spring security will see this message.
    @RequestMapping(value = "/login", method = RequestMethod.POST)
    public ModelAndView login(@RequestParam(value = "error", required = false) String error,
            @RequestParam(value = "logout", required = false) String logout) {

        ModelAndView m = new ModelAndView();
        if (error != null) {
            m.addObject("error", "Неверный логин и пароль");
        }

        if (logout != null) {
            m.addObject("msg", "Вы успешно вышли");
        }

        m.setViewName("login");
         redirAttrbs.addFlashAttribute("ключ", "параметр");
                 return new ModelAndView("redirect:/allStudents");
    }
}

StudentController
package adil.java.schoolmaven.controller;

import java.io.File;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletContext;
import adil.java.schoolmaven.entity.Student;
import adil.java.schoolmaven.service.StudentService;
import java.nio.file.FileSystemException;
import javax.servlet.http.HttpServletRequest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.lang.NonNull;
import org.springframework.stereotype.Controller;
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 org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class StudentController {

    @Autowired
    private ServletContext servletContext;

    // Constructor based Dependency Injection
    private StudentService studentService;

    public StudentController() {

    }

    @Autowired
    public StudentController(StudentService studentService) {
        this.studentService = studentService;
    }




    @RequestMapping(value = "/allStudents", method = {RequestMethod.GET, RequestMethod.POST})

    public ModelAndView displayAllUser() {
        System.out.println("User Page Requested : All Students");
        ModelAndView mv = new ModelAndView();
        List<Student> studentList = studentService.getAllStudents();
        mv.addObject("studentList", studentList);
        mv.setViewName("allStudents");
        return mv;
    }

    @RequestMapping(value = "/addStudent", method = RequestMethod.GET)
    public ModelAndView displayNewUserForm() {
        ModelAndView mv = new ModelAndView("addStudent");
        mv.addObject("headerMessage", "Add Student Details");
        mv.addObject("student", new Student());
        return mv;
    }

    @PostMapping(value = "/addStudent")
    public String saveNewStudent(@RequestParam("name") @NonNull String name,
            @RequestParam("surname") @NonNull String surname,
            @RequestParam("avatar") MultipartFile file)
            throws IOException {

        Student student = new Student();
        student.setSurname(surname);
        student.setName(name);

        if (file != null && !file.isEmpty()) {
            student.setAvatar(studentService.saveAvatarImage(file).getName());
        }

        studentService.saveStudent(student);
        return "redirect:/allStudents";
    }

    @GetMapping(value = "/editStudent/{id}")
    public ModelAndView displayEditUserForm(@PathVariable Long id) {
        ModelAndView mv = new ModelAndView("editStudent");
        Student student = studentService.getStudentById(id);
        mv.addObject("headerMessage", "Редактирование студента");
        mv.addObject("student", student);
        return mv;
    }

    @PostMapping(value = "/editStudent")
    public String saveEditedUser(
            @RequestParam("id") Long id,
            @RequestParam("name") String name,
            @RequestParam("surname") String surname,
            @RequestParam("avatar") MultipartFile file) {

        try {

            studentService.updateStudent(name, surname, file, studentService.getStudentById(id));

        } catch (FileSystemException ex) {
            ex.printStackTrace();
        } catch (IOException e) {
            return "redirect:/error";
        }

        return "redirect:/allStudents";
    }

    @GetMapping(value = "/deleteStudent/{id}")
    public ModelAndView deleteUserById(@PathVariable Long id) {
        studentService.deleteStudentById(id);
        ModelAndView mv = new ModelAndView("redirect:/allStudents");

        return mv;

    }

}