Jackson用Feign无法反序列化Spring的org.springframework.data.domain.Sort

Question

问题：假客户端对返回

Page<T>

的 Spring boot Rest API 进行 API 调用，无法反序列化该页面的

sort

属性。

• Spring Boot：2.3.3.发布
• Spring Cloud Feign：2.2.5.RELEASE

com.fasterxml.jackson.databind.exc.InvalidDefinitionException：不能 构造

org.springframework.data.domain.Sort

的实例（无 创建者，如默认构造函数，存在）：无法反序列化 对象值（无基于委托或基于属性的创建者）位于[来源： （缓冲阅读器）；行：1，列：238]（通过参考链： org.springframework.cloud.openfeign.support.PageJacksonModule$SimplePageImpl["排序"])

不知道为什么注册的

PageJacksonModule

似乎不支持这一点。

给定手动配置的 Feign 客户端：

public class TelematicsConfig {

  private String host;

  ObjectMapper provideObjectMapper() {
    return new ObjectMapper()
        .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
        .setPropertyNamingStrategy(SnakeCaseStrategy.SNAKE_CASE)
        .registerModule(new PageJacksonModule());
  }

  @Bean
  TelematicsClient provideTelematicsClient() {
    return Feign.builder()
        .client(new OkHttpClient())
        .encoder(new JacksonEncoder(provideObjectMapper()))
        .decoder(new JacksonDecoder(provideObjectMapper()))
        .logger(new Slf4jLogger(TelematicsClient.class))
        .logLevel(Logger.Level.FULL)
        .target(TelematicsClient.class, host);
  }

}

客户本身：

public interface TelematicsClient {

  @RequestLine("GET /api/v1/telematics/devices")
  Page<TelematicsDevice> getDevices();

}

当调用这个我得到：

2020-09-16 12:38:49.707 ERROR 96244 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is feign.FeignException: Cannot construct instance of `org.springframework.data.domain.Sort` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: (BufferedReader); line: 1, column: 238] (through reference chain: org.springframework.cloud.openfeign.support.PageJacksonModule$SimplePageImpl["sort"]) reading GET http://localhost:8081/api/v1/telematics/devices] with root cause

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `org.springframework.data.domain.Sort` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: (BufferedReader); line: 1, column: 238] (through reference chain: org.springframework.cloud.openfeign.support.PageJacksonModule$SimplePageImpl["sort"])
    at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:67)
    at com.fasterxml.jackson.databind.DeserializationContext.reportBadDefinition(DeserializationContext.java:1611)
    at com.fasterxml.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:400)
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1077)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1320)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:331)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:164)
    at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:542)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeWithErrorWrapping(BeanDeserializer.java:535)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeUsingPropertyBased(BeanDeserializer.java:419)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1310)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:331)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:164)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4482)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3463)
    at feign.jackson.JacksonDecoder.decode(JacksonDecoder.java:61)

任何关于为什么这不起作用的见解将不胜感激。

编辑：下面的类似乎暗示支持排序，不是吗？

https://github.com/spring-cloud/spring-cloud-openfeign/blob/master/spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/support/PageJacksonModule。 java#L69

Answer 1

如果您使用自动配置的 Feign 客户端，您可以按照 Spring Cloud OpenFeign 文档 打开相应的配置属性：

您可以考虑启用 Jackson 模块来获得支持

org.springframework.data.domain.Page

和

org.springframework.data.domain.Sort

解码。

feign.autoconfiguration.jackson.enabled=true

Answer 2

找到答案了。

https://github.com/spring-cloud/spring-cloud-openfeign/blob/master/spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/support/SortJacksonModule。 java

    return new ObjectMapper()
        .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
        .setPropertyNamingStrategy(SnakeCaseStrategy.SNAKE_CASE)
        .registerModule(new PageJacksonModule())
        .registerModule(new SortJacksonModule()); // <-- This.  duh.

Answer 3

尝试添加：

    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-openfeign-core</artifactId>
        <version>3.1.3</version>
        <scope>compile</scope>
    </dependency>

Answer 4

您可以通过添加 openfeign-core 依赖来获取这些模块：

implementation "org.springframework.cloud:spring-cloud-openfeign-core"

但这在 Spring Boot 3 中不再适用于

SortJacksonModule

。

例如：

代码（Kotlin）

private val mapper = jacksonObjectMapper().registerModules(
    PageJacksonModule(),
    SortJacksonModule(),
    JavaTimeModule(),
)

配置：

抛出此异常：

java.lang.NoClassDefFoundError: feign/codec/EncodeException at org.springframework.cloud.openfeign.support.SortJacksonModule.setupModule(SortJacksonModule.java:47)

分辨率

OpenFeign spring 团队正在等待投票，以便花时间解决这个问题。请务必在这里对该问题进行投票：

https://github.com/spring-cloud/spring-cloud-openfeign/issues/675

Answer 5

我解决假客户端的

Sort

和

Page

问题的解决方案如下：

---

1. 创建

   CustomPageDeserializer<T>

   类型的类：

   import com.fasterxml.jackson.core.JsonParser; 
   import com.fasterxml.jackson.databind.DeserializationContext; 
   import com.fasterxml.jackson.databind.JsonDeserializer; 
   import com.fasterxml.jackson.databind.JsonNode; 
   import com.fasterxml.jackson.databind.ObjectMapper; 
   import org.springframework.data.domain.PageImpl; 
   import org.springframework.data.domain.PageRequest;
   import java.io.IOException; 
   import java.util.List;
   
   public class CustomPageDeserializer<T> extends JsonDeserializer<PageImpl<T>> {
   
       private final Class<T> contentClass;
   
       public CustomPageDeserializer(Class<T> contentClass) {
           this.contentClass = contentClass;
       }
   
       @Override
       public PageImpl<T> deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
           ObjectMapper mapper = (ObjectMapper) jsonParser.getCodec();
           JsonNode root = mapper.readTree(jsonParser);
           JsonNode content = root.get("content");
           List<T> contentList = mapper.readValue(content.traverse(), mapper.getTypeFactory().constructCollectionType(List.class, contentClass));
           int totalElements = root.get("totalElements").asInt();
           int totalPages = root.get("totalPages").asInt();
           int number = root.get("number").asInt();
   
           int pageSize = contentList.isEmpty() ? 1 : contentList.size();
           return new PageImpl<>(contentList, PageRequest.of(number, pageSize), totalElements);
       } } 
   

2. 创建班级

   CustomPageModule

   :

   import com.fasterxml.jackson.databind.module.SimpleModule; 
   import org.springframework.data.domain.PageImpl;
   
   public class CustomPageModule  extends SimpleModule {
       public CustomPageModule(Class<?> contentClass) {
           addDeserializer(PageImpl.class, new CustomPageDeserializer<>(contentClass));
       } }
   

3. 创建班级

   MyFeignClientConfiguration

   :

   import com.fasterxml.jackson.databind.ObjectMapper; 
   import feign.codec.Decoder; 
   import feign.optionals.OptionalDecoder; 
   import org.springframework.boot.autoconfigure.http.HttpMessageConverters;
   import org.springframework.cloud.openfeign.support.ResponseEntityDecoder;
   import org.springframework.cloud.openfeign.support.SpringDecoder;
   import org.springframework.context.annotation.Bean; 
   import org.springframework.context.annotation.Configuration; 
   import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
   
   @Configuration 
   public class MyFeignClientConfiguration {
       @Bean
       public Decoder feignDecoder() {
           ObjectMapper objectMapper = new ObjectMapper();
           objectMapper.registerModule(new CustomPageModule(MyEntity.class));
           return new OptionalDecoder(new ResponseEntityDecoder(new SpringDecoder(() -> new HttpMessageConverters(new
   MappingJackson2HttpMessageConverter(objectMapper)))));
       } } 
   

4. 创建班级

   MyFeignClient

   :

   import org.springframework.cloud.openfeign.FeignClient; 
   import org.springframework.http.ResponseEntity; 
   import org.springframework.web.bind.annotation.GetMapping; 
   import java.util.List;
   
   @FeignClient(name = "myFeignClient", url =
   "${my.service.feign.url}", configuration =
   MyFeignClientConfiguration.class) 
   public interface MyFeignClient {
   
       @GetMapping("/api/action/products")
       ResponseEntity<List<String>> getAvailableProducts(); }