如何在Spring Boot中验证Rest请求

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

@RestController
@RequestMapping("/api")
public class ApiController {
    // REST请求处理方法
}

@GetMapping("/users/{id}")
public ResponseEntity<User> getUser(@PathVariable Long id) {
    // 处理获取用户信息的逻辑
}

@PostMapping("/users")
public ResponseEntity<User> createUser(@Valid @RequestBody User user, BindingResult bindingResult) {
    // 处理创建用户的逻辑
}

public class User {
    @NotBlank(message = "用户名不能为空")
    private String username;

    @Size(min = 6, max = 20, message = "密码长度必须在6到20之间")
    private String password;

    // 其他属性和方法
}

@PostMapping("/users")
public ResponseEntity<User> createUser(@Valid @RequestBody User user, BindingResult bindingResult) {
    if (bindingResult.hasErrors()) {
        // 处理验证失败的情况
    } else {
        // 处理验证成功的情况
    }
}