File upload spring cloud feign client

Question

When make a post request from one microservice to another using feign client of spring cloud netflix, I get the following error in Postman :

{
"timestamp": 1506933777413,
"status": 500,
"error": "Internal Server Error",
"exception": "feign.codec.EncodeException",
"message": "Could not write JSON: No serializer found for class java.io.FileDescriptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class java.io.FileDescriptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: org.springframework.web.multipart.support.StandardMultipartHttpServletRequest$StandardMultipartFile[\"inputStream\"]->java.io.FileInputStream[\"fd\"])",
"path": "/attachments"
}

And my eclipse console shows the following exception :

com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class java.io.FileDescriptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: org.springframework.web.multipart.support.StandardMultipartHttpServletRequest$StandardMultipartFile["inputStream"]->java.io.FileInputStream["fd"]) at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:284) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.SerializerProvider.mappingException(SerializerProvider.java:1110) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.SerializerProvider.reportMappingProblem(SerializerProvider.java:1135) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:69) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:32) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:704) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:689) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:704) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:689) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:292) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1429) ~[jackson-databind-2.8.9.jar:2.8.9] at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:951) ~[jackson-databind-2.8.9.jar:2.8.9]

UPDATE 1

This is my feign interface :

@FeignClient(name="attachment-service", fallback=AttachmentHystrixFallback.class)
public interface AttachmentFeignClient {

@RequestMapping("upload")
void upload(@RequestPart(name="file") MultipartFile file, @RequestParam(name="attachableId") Long attachableId, 
        @RequestParam(name="className") String className, @RequestParam(name="appName") String appName);

And this is the main microservice controller :

@RestController
public class AttachmentController implements Serializable {

/**
 * 
 */
private static final long serialVersionUID = -4431842080646836475L;

@Autowired
AttachmentService attachmentService;

@RequestMapping(value = "attachments", method = RequestMethod.POST, consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
public void upload(@RequestPart MultipartFile file, @RequestParam Long attachableId, @RequestParam String className, @RequestParam String appName) throws Exception {
    attachmentService.uploadFile(file, attachableId, className, appName);
}

}

I'm certainly missing some kind of serializer here
Any suggestion would be appreciated !
Thanks

Answer 1

After few days searching a solution I found this. You should start to add feign form for spring dependency :

<dependency>
   <groupId>io.github.openfeign.form</groupId>
   <artifactId>feign-form-spring</artifactId>
   <version>3.3.0</version>
</dependency

Then your feign client need this spring form encoder :

@FeignClient(name="attachment-service",  configuration = {AttachmentFeignClient.MultipartSupportConfig.class}
 fallback=AttachmentHystrixFallback.class)
public interface AttachmentFeignClient {

@RequestMapping(value= {"upload"}, consumes = {"multipart/form-data"})
void upload(@RequestPart(name="file") MultipartFile file, @RequestParam(name="attachableId") Long attachableId, 
        @RequestParam(name="className") String className, @RequestParam(name="appName") String appName);

 public class MultipartSupportConfig {
    @Bean
    @Primary
    @Scope("prototype")
    public Encoder feignFormEncoder() {
        return new SpringFormEncoder();
    }
  }
}

I hope it will help someone.

Answer 2

TL;DR
Transform your MultiPartFile to MultiValueMap. See example below

---

The answer mentioned by @martin-choraine is the proper and the best answer to have your FeignClient method signature, the same as the actual endpoint signature that you are trying to call. However, there is a way around that does not require you to define a FormEncoder or add any extra dependency because in some applications you are not allowed to do that (enterprise shit); all what you need is to transform your MultipartFile to a MultiValueMap and it will perfectly work as the standard encoder will be able to serialize it.

---

Actual EndPoint to be called

@PostMapping(path = "/add", consumes = MULTIPART_FORM_DATA_VALUE, produces = APPLICATION_JSON_VALUE)
 public MyResponseObject add(@RequestParam(name = "username") String username,
                             @RequestPart(name = "filetoupload") MultipartFile file) {
              Do something
}

The POST method in your FeignClient should look like this

@PostMapping(path = "/myApi/add", consumes = MULTIPART_FORM_DATA_VALUE, 
              produces = APPLICATION_JSON_VALUE)
 public MyResponseObject addFile(@RequestParam(name = "username") String username,
                           @RequestPart(name = "filetoupload") MultiValueMap<String, Object> file);

Then when you call the addFile you should provide MultiValueMap like this

public MyResponseObject addFileInAnotherEndPoint(String username, MultipartFile file) throws IOException {

    MultiValueMap<String, Object> multiValueMap = new LinkedMultiValueMap<>();
    ByteArrayResource contentsAsResource = new ByteArrayResource(file.getBytes()) {
        @Override
        public String getFilename() {
            return file.getOriginalFilename();
        }
    };
    multiValueMap.add("filetoupload", contentsAsResource);
    multiValueMap.add("fileType", file.getContentType());
    return this.myFeignClient.addFile(username, multiValueMap);
}