如何在Feign Client中配置请求体日期的指定格式序列化？

问题描述 #

用Feign Client调用第三方API时，请求体里的日期格式是这样的：

{
  "requestTime": "2023-06-07T12:18:00.916+00:00"
}

但第三方API只认yyyy-MM-dd'T'HH:mm:ss.SSSZ格式的日期，合法的请求体示例是：

{
  "requestTime": "2023-06-17T14:53:47.402Z"
}

现有代码 #

Feign Client接口 #

@FeignClient(value = "myfeign", url = "https://myfeign.com/")
public interface MyFeignClient {

    @PostMapping(value = "/myfeign/", produces = APPLICATION_JSON_VALUE, consumes = APPLICATION_JSON_VALUE)
    MyResponse sendRequest(MyRequest request);
}

openapi-generator生成的MyRequest类 #

public class MyRequest {
   @JsonProperty("requestTime")
   @DateTimeFormat(iso = DateTimeFormat.ISO.DATE_TIME)
   private Date requestTime;
   // getter...
}

尝试过的无效配置 #

Feign配置类

public class MyFeignConfig {

    @Bean
    public Encoder feignEncoder() {
        HttpMessageConverter<Object> jacksonConverter = new MappingJackson2HttpMessageConverter(objectMapper());

        HttpMessageConverters httpMessageConverters = new HttpMessageConverters(jacksonConverter);
        ObjectFactory<HttpMessageConverters> objectFactory = () -> httpMessageConverters;


        return new SpringEncoder(objectFactory);
    }

    private ObjectMapper objectMapper() {
        final String DATE_FORMAT = "yyyy-MM-dd'T'mm:HH:ss.SSSZ";
        SimpleDateFormat dateFormat = new SimpleDateFormat((DATE_FORMAT));
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setDateFormat(dateFormat);
    }
}

修改后的Feign Client

@FeignClient(value = "myfeign", url = "https://myfeign.com/",  configuration = "MyFeignConfig.class")
public interface MyFeignClient {

    @PostMapping(value = "/myfeign/", produces = APPLICATION_JSON_VALUE, consumes = APPLICATION_JSON_VALUE)
    MyResponse sendRequest(MyRequest request);
}

问题分析 #

1. 日期格式写错了：你配置的DATE_FORMAT把小时和分钟的格式搞反了，应该是HH:mm（24小时制小时在前），不是mm:HH，正确格式是yyyy-MM-dd'T'HH:mm:ss.SSSZ。
2. ObjectMapper没返回：objectMapper()方法最后没返回配置好的ObjectMapper实例，等于白配置了。
3. FeignClient配置引用错误：configuration属性要传类对象MyFeignConfig.class，不是字符串"MyFeignConfig.class"。
4. @DateTimeFormat没用：这个注解是Spring MVC用来绑定请求参数的，对Jackson序列化日期根本不起作用，得用Jackson的注解。

解决步骤 #

1. 修正Feign配置类 #

把格式写错的地方改过来，还要记得返回ObjectMapper：

public class MyFeignConfig {

    @Bean
    public Encoder feignEncoder() {
        HttpMessageConverter<Object> jacksonConverter = new MappingJackson2HttpMessageConverter(objectMapper());
        HttpMessageConverters httpMessageConverters = new HttpMessageConverters(jacksonConverter);
        ObjectFactory<HttpMessageConverters> objectFactory = () -> httpMessageConverters;
        return new SpringEncoder(objectFactory);
    }

    private ObjectMapper objectMapper() {
        final String DATE_FORMAT = "yyyy-MM-dd'T'HH:mm:ss.SSSZ";
        SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setDateFormat(dateFormat);
        // 必须返回配置好的ObjectMapper
        return objectMapper;
    }
}

2. 修正FeignClient的配置引用 #

去掉configuration属性的引号，直接传类对象：

@FeignClient(value = "myfeign", url = "https://myfeign.com/", configuration = MyFeignConfig.class)
public interface MyFeignClient {

    @PostMapping(value = "/myfeign/", produces = APPLICATION_JSON_VALUE, consumes = APPLICATION_JSON_VALUE)
    MyResponse sendRequest(MyRequest request);
}

3. 给MyRequest加Jackson注解（可选但更稳妥） #

为了避免全局配置被其他地方覆盖，直接在MyRequest的日期字段上加Jackson的@JsonFormat注解，明确指定序列化格式：

public class MyRequest {
   @JsonProperty("requestTime")
   @JsonFormat(pattern = "yyyy-MM-dd'T'HH:mm:ss.SSSZ", timezone = "GMT")
   private Date requestTime;
   // getter...
}

4. 验证结果 #

配置完之后，请求体里的日期就会变成符合要求的格式：

{
  "requestTime": "2023-06-17T14:53:47.402Z"
}

内容的提问来源于stack exchange，提问作者ikhvjs