Master SpringBoot 3.2.5: 9 Essential Techniques to Access Request Data

1. Optional Parameter Wrapping

Wrap request parameters with java.util.Optional to make them optional, equivalent to using @RequestParam(required=false).

@GetMapping("/optional")
public Object optional(Optional<String> name) {
    return String.format("请求参数: %s", name.orElse(""));
}

2. Convenient Access to Servlet API

Inject WebRequest or NativeWebRequest to obtain HttpServletRequest, HttpServletResponse, HttpSession, etc., or declare the specific objects directly.

@GetMapping("/servlet/api")
public Object servletApi(WebRequest request, NativeWebRequest webRequest) {
    String name = request.getParameter("name");
    HttpServletRequest req = webRequest.getNativeRequest(HttpServletRequest.class);
    HttpServletResponse resp = webRequest.getNativeResponse(HttpServletResponse.class);
    HttpSession session = webRequest.getNativeRequest(HttpSession.class);
    return "servlet api";
}

public Object servletApi(HttpServletRequest req, HttpServletResponse resp) {
    // ...
}

3. Retrieve the Current Authenticated User

Inject java.security.Principal (or Authentication) to get the logged‑in user when Spring Security is used.

@GetMapping("/principal")
public Object principal(Principal principal) {
    return principal;
}

4. Access Other Request Information

Inject HttpMethod and Locale to obtain the request method and locale, or use java.util.TimeZone / java.time.ZoneId for time‑zone data.

@GetMapping("/other")
public Object other(HttpMethod method, Locale locale) {
    return method.name() + ", " + locale.toString();
}
// Output example: GET, zh_CN

5. Read Request Body as InputStream

Accept an InputStream parameter to read the raw request body.

@PostMapping("/inputStream")
public Object inputStream(InputStream is) throws Exception {
    return String.format("读取到内容: %s",
        StreamUtils.copyToString(is, StandardCharsets.UTF_8));
}

6. Get Headers and Body via HttpEntity

Use HttpEntity<String> to access request headers and body together.

@PostMapping("/httpentity")
public Object httpentity(HttpEntity<String> entity) {
    return Map.of(
        "headers", entity.getHeaders(),
        "body", entity.getBody()
    );
}

7. Build Current Request URI

Inject UriComponentsBuilder to obtain the full request URI (scheme, host, port, context).

@GetMapping("/uri")
public Object uri(UriComponentsBuilder builder) {
    return builder.toUriString();
}

http://localhost:9001/api

8. Handle Multipart Request Parts

Use @RequestPart to retrieve individual parts of a multipart/form‑data request, either as simple values or as JSON‑deserialized objects (remember to set the part’s Content‑Type).

@PostMapping("/requestpart")
public Object requestpart(@RequestPart("user") String user) {
    return user;
}

public Object requestpart(@RequestPart("user") User user)

When sending a JSON object, the part must include Content-Type: application/json; otherwise a 415 error occurs.

9. Pass Flash Attributes on Redirect

Use RedirectAttributes to add flash attributes that survive a redirect.

@PostMapping("/")
public String handleFileUpload(RedirectAttributes redirectAttributes) {
    redirectAttributes.addFlashAttribute("message", "You successfully uploaded file!");
    return "redirect:/";
}

These attributes can be accessed on the redirected page.