如何在Spring boot中使用Spring验证来验证嵌套对象？

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
</dependency>

public class User {
    private String name;
    @Valid
    private Address address;
    // getters and setters
}

public class Address {
    @NotBlank(message = "City is required")
    private String city;
    // getters and setters
}

@RestController
public class UserController {
    @PostMapping("/users")
    public ResponseEntity<String> createUser(@Valid @RequestBody User user) {
        // 处理创建用户的逻辑
        return ResponseEntity.ok("User created successfully");
    }
}

@ControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<String> handleValidationException(MethodArgumentNotValidException ex) {
        BindingResult bindingResult = ex.getBindingResult();
        List<FieldError> fieldErrors = bindingResult.getFieldErrors();
        StringBuilder errorMessage = new StringBuilder();
        for (FieldError fieldError : fieldErrors) {
            errorMessage.append(fieldError.getDefaultMessage()).append("; ");
        }
        return ResponseEntity.badRequest().body(errorMessage.toString());
    }
}