有没有一种方法将Java Bean验证API与Spring RestTemplate集成？

Question

有没有一种方法可以将Spring RestTemplate与JavaBean验证API集成？

我知道Spring控制器有一种集成方式。您可以在请求体参数上放置@Valid，如果Employee无效，则会收到MethodArgumentNotValidException异常。您可以在异常处理程序类中处理该异常。

  @PostMapping(value = "/add", produces = APPLICATION_JSON_VALUE)
  public ResponseEntity<String> addEmployee(
       @RequestBody @Valid Employee emp) {

    //...

  }

但我想要的是一种类似于验证从Spring RestTemplate响应的方式，就像这样调用时 - 我希望从Spring得到相同(或者其他)的异常。

Employee emp = template.exchange("http:///someUrl", HttpMethod.GET, null);

我知道可以这样注入验证器，并在响应上调用validator.validate(..)。

  @Autowired
  private Validator validator;

但我不想每次都手动执行此操作。

- user1321466

---

你需要做什么样的用例才需要这样做呢？从技术上讲，我真的想不出一个不使用验证器对象的情况，除非它是某种代理服务... 手动验证也可以，有时甚至更有用。 - Chad

谢谢回复。我只是想知道在Spring中是否有一些解决方案。我有很多的res调用，我不想在每个从restTemplate返回的对象上调用validate方法。 - user1321466

Answer 1

您可以继承RestTemplate并在从原始数据中提取响应后立即验证响应。

示例：

public class ValidatableRestTemplate extends RestTemplate {

    private final Validator validator;

    public ValidatableRestTemplate(Validator validator) {
        this.validator = validator;
    }

    @Override
    protected <T> T doExecute(URI url, HttpMethod method, RequestCallback requestCallback, ResponseExtractor<T> responseExtractor) throws RestClientException {
        final T response = super.doExecute(url, method, requestCallback, responseExtractor);
        Object  body;
        if (response instanceof ResponseEntity<?>) {
            body = ((ResponseEntity) response) .getBody();
        } else {
            body = response;
        }
        final Set<ConstraintViolation<Object>> violations = validator.validate(body);
        if (violations.isEmpty()) {
            return response;
        }

        throw new ConstraintViolationException("Invalid response", violations);
    }
}

使用方法很简单，只需将您的子类定义为RestTemplate bean即可。

完整示例：

@SpringBootApplication
public class So45333587Application {

    public static void main(String[] args) { SpringApplication.run(So45333587Application.class, args); }

    @Bean
    RestTemplate restTemplate(Validator validator) { return new ValidatableRestTemplate(validator); }

    public static class ValidatableRestTemplate extends RestTemplate {
        private final Validator validator;

        public ValidatableRestTemplate(Validator validator) { this.validator = validator; }

        @Override
        protected <T> T doExecute(URI url, HttpMethod method, RequestCallback requestCallback, ResponseExtractor<T> responseExtractor) throws RestClientException {
            final T response = super.doExecute(url, method, requestCallback, responseExtractor);
            Object  body;
            if (response instanceof ResponseEntity<?>) {
                body = ((ResponseEntity) response).getBody();
            } else {
                body = response;
            }
            final Set<ConstraintViolation<Object>> violations = validator.validate(body);
            if (violations.isEmpty()) {
                return response;
            }

            throw new ConstraintViolationException("Invalid response", violations);
        }
    }

    @JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)
    public static class Post {
        @Min(2) // change to '1' and constraint violation will disappear
        private Long   id;
        private Long   userId;
        private String title;
        private String body;

        @Override
        public String toString() { 
            return String.format("Post{id=%d, userId=%d, title='%s', body='%s'}", id, userId, title, body); 
        }
    }

    @Bean
    CommandLineRunner startup(RestTemplate restTemplate) {
        return args -> {
            final ResponseEntity<Post> entity = restTemplate.exchange("https://jsonplaceholder.typicode.com/posts/1", HttpMethod.GET, null, Post.class);
            System.out.println(entity.getBody());
        };
    }
}

- Bohdan Levchenko