@GetMapping("/index2")
public String doGet(Model model) {
    model.addAttribute("sr", new StudentRequest());
    return "index.html";
}

@PostMapping("/index2")
public String doPost(Model model, @ModelAttribute("sr") StudentRequest sr) {
    studentService.saveStudent(sr);
    model.addAttribute("name", sr.name);
    return "output.html";
}

private String name;
private int grade;

public void setName(String name){
    this.name = name;
}

public void setGrade(int grade){
    this.grade = grade;
}

public int grade;

public String getName(){
    return name;
}
public int getGrade(){
    return grade;
}
public void setName(String name){
    this.name = name;
}
public void setGrade(int grade){
    this.grade = grade;
}

<form th:object="${sr}" method="post" action="index2">
    이름 <input th:field="*{name}">
    학년 <input th:field="*{grade}">
    <button>전달</button>
</form>