@RequestHeaderの使い方と引数を徹底解説！【初心者向け】

@RestController
@RequestMapping("/api")
public class UserController {

    @GetMapping("/profile")
    public String getProfile(@RequestHeader("Authorization") String token) {
        if ("my-secret-token".equals(token)) {
            return "こんにちは！あなたのプロフィールです";
        }
        return "アクセスできません！トークンが違います";
    }
}

GET http://localhost:8080/api/profile
Headers:
Authorization: my-secret-token

@RequestMapping("/header-example")
public ResponseEntity<String> getHeaderInfo(@RequestHeader(value = "User-Agent", defaultValue = "Unknown") String userAgent) {
    return ResponseEntity.ok("User-Agent: " + userAgent);
}

@RequestMapping("/multiple-headers")
public ResponseEntity<String> getMultipleHeaders(
        @RequestHeader("User-Agent") String userAgent, 
        @RequestHeader("Accept-Language") String language) {
    return ResponseEntity.ok("User-Agent: " + userAgent + ", Accept-Language: " + language);
}

@RequestMapping("/content-length")
public ResponseEntity<String> getContentLength(@RequestHeader("Content-Length") int contentLength) {
    return ResponseEntity.ok("Content-Length: " + contentLength);
}

@RequestMapping("/get-header")
public ResponseEntity<String> getHeader(@RequestHeader("Authorization") String authToken) {
    return ResponseEntity.ok("Authorization header: " + authToken);
}

@RequestMapping("/get-header")
public ResponseEntity<String> getHeader(@RequestHeader(value = "X-Custom-Header", defaultValue = "default-value") String customHeader) {
    return ResponseEntity.ok("Custom Header: " + customHeader);
}

@RequestMapping("/get-header")
public ResponseEntity<String> getHeader(@RequestHeader(value = "X-Custom-Header", required = false) String customHeader) {
    return ResponseEntity.ok("Custom Header: " + (customHeader == null ? "No header" : customHeader));
}