Springboot javax验证不起作用

<dependency>
    <groupId>javax.validation</groupId>
    <artifactId>validation-api</artifactId>
    <version>2.0.1.Final</version>
</dependency>

public class User {
    @NotNull(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个字符之间")
    private String password;

    @Email(message = "邮箱格式不正确")
    private String email;

    // 省略其他字段和方法
}

@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("用户创建成功");
    }
}