Spring MVC CRUD

public class Student {
    private int id;
    private String name;
    private String email;
    private int age;
    
    // constructors, getters, setters
}

@Controller
@RequestMapping("/students")
public class StudentController {
    
    // In-memory list (instead of database)
    private List students = new ArrayList<>();
    private int nextId = 1;
    
    // CREATE - Show form
    @GetMapping("/new")
    public String showNewForm(Model model) {
        model.addAttribute("student", new Student());
        return "student-form";
    }
    
    // CREATE - Save student
    @PostMapping("/save")
    public String saveStudent(@ModelAttribute Student student) {
        student.setId(nextId++);
        students.add(student);
        return "redirect:/students";
    }
    
    // READ - List all students
    @GetMapping
    public String listStudents(Model model) {
        model.addAttribute("students", students);
        return "student-list";
    }
    
    // UPDATE - Show edit form
    @GetMapping("/edit/{id}")
    public String showEditForm(@PathVariable int id, Model model) {
        Student student = students.stream().filter(s -> s.getId() == id).findFirst().orElse(null);
        model.addAttribute("student", student);
        return "student-form";
    }
    
    // UPDATE - Save edited student
    @PostMapping("/update/{id}")
    public String updateStudent(@PathVariable int id, @ModelAttribute Student updatedStudent) {
        for (Student s : students) {
            if (s.getId() == id) {
                s.setName(updatedStudent.getName());
                s.setEmail(updatedStudent.getEmail());
                s.setAge(updatedStudent.getAge());
                break;
            }
        }
        return "redirect:/students";
    }
    
    // DELETE
    @GetMapping("/delete/{id}")
    public String deleteStudent(@PathVariable int id) {
        students.removeIf(s -> s.getId() == id);
        return "redirect:/students";
    }
}

• CRUD = Create, Read, Update, Delete.
• Use @GetMapping for showing forms and @PostMapping for saving data.
• @PathVariable captures values from URL (like id).
• @ModelAttribute binds form data to Java object.
• Redirect prevents duplicate form submissions.