SpringBoot 3.3: Annotations @ModelAttribute, @SessionAttribute, @RequestAttribute
This article explains the purpose and proper usage of SpringBoot 3.3’s request‑handling annotations—@ModelAttribute, @SessionAttribute, @RequestAttribute—and the RedirectAttributes class, providing detailed code examples, configuration tips, and scenarios where each tool is essential for form submission, session management, and flash‑attribute redirects.
Environment: SpringBoot 3.3.0
1. Introduction
In SpringBoot development, traditional request attribute handling annotations such as @ModelAttribute, @SessionAttribute, @RequestAttribute and the class RedirectAttributes are used less frequently, but they remain indispensable in specific scenarios like form submission, session state management, and redirect attribute passing.
@ModelAttribute: Binds request data to method parameters or model attributes, simplifying complex object binding for forms and allowing pre‑processing of incoming data or initialization of command objects.
@SessionAttribute: Retrieves attributes from HttpSession, useful for storing non‑sensitive user information or temporary data such as user settings or shopping‑cart contents.
@RequestAttribute: Allows passing custom attributes via HttpServletRequest between controllers, suitable for data that does not need to persist across requests.
RedirectAttributes: Used during redirects to pass flash attributes that are available for the next request only, ideal for showing success/failure messages while keeping URLs clean.
2. Practical Examples
2.1 @ModelAttribute
Used on method parameters:
@GetMapping("/product/{cateId}/{id}")
public ProductDTO test(@ModelAttribute ProductDTO dto) {
return dto;
}When using Thymeleaf, the bound ProductDTO can be accessed directly in the view.
@GetMapping("/product/{cateId}/{id}")
public String test(@ModelAttribute ProductDTO dto) {
return "modelattribute";
}<div th:if="${productDTO}">
<ul>
<li>cateId: <a th:text="${productDTO.cateId}"></a></li>
<li>id: <a th:text="${productDTO.id}"></a></li>
</ul>
</div>Default model key is the class name with the first letter lower‑cased; it can be customized:
public String test(@ModelAttribute("dto") ProductDTO dto) { ... }Used on a method:
@GetMapping("/product/{cateId}/{id}")
public String test() {
return "modelattribute";
}
@ModelAttribute("dto")
public ProductDTO dto(ProductDTO dto) {
System.out.println("dto....");
return dto;
}2.2 @SessionAttribute
Only applicable to method parameters. Example reads a User object from the session:
@GetMapping("/user")
@ResponseBody
public User user(@SessionAttribute("user") User user) {
return user;
}
// Simulate login and store User in session
@GetMapping("/login")
@ResponseBody
public String login(HttpSession session) {
session.setAttribute("user", new User(666L, "Admin"));
return "login success";
}If the session lacks the attribute, an error occurs; it can be avoided by marking the attribute as optional:
public User user(@SessionAttribute(value = "user", required = false) User user) { ... }public User user(@SessionAttribute("user") Optional<User> user) { ... }2.3 @RequestAttribute
Also limited to method parameters. It can retrieve attributes set earlier by a servlet filter or interceptor:
@Component
public class UserFilter extends OncePerRequestFilter {
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
request.setAttribute("user", new User(888L, "Guest"));
filterChain.doFilter(request, response);
}
}@GetMapping("/user")
@ResponseBody
public User user(@RequestAttribute("user") Optional<User> user) {
return user.orElse(new User());
}2.4 RedirectAttributes
During a redirect, flash attributes can be added to RedirectAttributes and accessed in the target view:
@GetMapping("")
public String index(RedirectAttributes ra) {
ra.addFlashAttribute("message", "hello");
return "redirect:/page/tm";
}
@GetMapping("tm")
public String tm(RedirectAttributes ra) {
return "test";
}<body>
<h1>Test Page</h1>
<div th:if="${message}">
<h2 th:text="${message}" />
</div>
</body>After the redirect, the flash attribute message is available in the rendered page.
These examples demonstrate when and how to apply the four annotations/classes in SpringBoot 3.3 to handle form data, session data, request‑scoped attributes, and flash messages effectively.
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