Feign调用时ResponseEntity反序列化失败问题求助

错误信息 #

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of 
`org.springframework.http.ResponseEntity` (no Creators, like default constructor, exist): cannot deserialize 
from Object value (no delegate- or property-based Creator)
 at [Source: (BufferedReader); line: 1, column: 2]

相关代码 #

控制器端点 #

@RestController
@RequestMapping(Routes.URI_PREFIX)
public class CartoController {

@Autowired
private ReadCartographyApiDelegate readCartographyApiDelegate;

@GetMapping(value = "/cartographies/{uid}", produces = {MediaType.APPLICATION_JSON_VALUE})
public ResponseWrapper<ReadCartographyResponse> readCarto(HttpServletRequest request,
                                            @PathVariable(name = "uid") String uid) {
   ResponseEntity<ReadCartographyResponse> result ;
   try {
      result = readCartographyApiDelegate.readCartography(uid);
   }catch (Exception e){
      throw new TechnicalException("Error during read Carto");
   }
   return responseWrapperWithIdBuilder.of(result.getBody());
   }
 }

OpenAPI自动生成的ReadCartographyApiDelegate接口 #

@javax.annotation.Generated(value = "org.openapitools.codegen.languages.SpringCodegen", date = "...")
public interface ReadCartographyApiDelegate {

    default Optional<NativeWebRequest> getRequest() {
        return Optional.empty();
    }
    default ResponseEntity<ReadCartographyResponse> readCartography(String uid) {
        getRequest().ifPresent(request -> {
            for (MediaType mediaType: MediaType.parseMediaTypes(request.getHeader("Accept"))) {
                if (mediaType.isCompatibleWith(MediaType.valueOf("application/json"))) {
                    String exampleString = "null";
                    ApiUtil.setExampleResponse(request, "application/json", exampleString);
                    break;
                }
            }
        });
        return new ResponseEntity<>(HttpStatus.NOT_IMPLEMENTED);

    }

}

实现类ReadCartographyApiDelegateImpl #

@Service
public class ReadCartographyApiDelegateImpl implements ReadCartographyApiDelegate {

    private EcomGtmClient ecomGtmClient;

    public ReadCartographyApiDelegateImpl(EcomGtmClient ecomGtmClient) {
        this.ecomGtmClient = ecomGtmClient;
    }

    @Override
    public ResponseEntity<ReadCartographyResponse> readCartography(String uid) {
        ResponseEntity<ReadCartographyResponse> response = ecomGtmClient.readCartography(uid);
        return response;
    }
}

Feign客户端EcomGtmClient #

@FeignClient(name = "ecomGtmSvc", url = "http://localhost/")
public interface EcomGtmClient {
    @GetMapping(value = "/read-carto/{uid}")
    ResponseEntity<ReadCartographyResponse> readCartography(@PathVariable("uid") String uid);
}

问题分析 #

已知问题在于Spring的ResponseEntity类没有默认构造方法，导致Jackson反序列化时无法创建实例。

解决方案 #

方案1：直接返回业务对象（推荐） #

Feign本身会自动处理HTTP响应的状态码，无需用ResponseEntity包裹返回结果。修改Feign客户端的返回类型为业务对象ReadCartographyResponse，再在实现类中手动封装成ResponseEntity：

修改EcomGtmClient：

@FeignClient(name = "ecomGtmSvc", url = "http://localhost/")
public interface EcomGtmClient {
    @GetMapping(value = "/read-carto/{uid}")
    ReadCartographyResponse readCartography(@PathVariable("uid") String uid);
}

修改ReadCartographyApiDelegateImpl：

@Override
public ResponseEntity<ReadCartographyResponse> readCartography(String uid) {
    ReadCartographyResponse responseBody = ecomGtmClient.readCartography(uid);
    return ResponseEntity.ok(responseBody);
}

方案2：配置Jackson支持ResponseEntity反序列化 #

通过注册Spring提供的Jackson模块，让Jackson能够正确序列化/反序列化ResponseEntity：

创建Feign配置类，自定义Decoder并注册SpringModule：

@Configuration
public class FeignConfig {
    @Bean
    public Decoder feignDecoder(ObjectMapper objectMapper) {
        objectMapper.registerModule(new SpringModule());
        return new JacksonDecoder(objectMapper);
    }
}

在Feign客户端上指定该配置：

@FeignClient(name = "ecomGtmSvc", url = "http://localhost/", configuration = FeignConfig.class)
public interface EcomGtmClient {
    @GetMapping(value = "/read-carto/{uid}")
    ResponseEntity<ReadCartographyResponse> readCartography(@PathVariable("uid") String uid);
}

注意：确保项目依赖了spring-web模块，SpringModule包含在该模块中。

内容的提问来源于stack exchange，提问作者Wijdane KHATTAT