Feign ErrorDecoder : retrieve the original message

Question

I use a ErrorDecoder to return the right exception rather than a 500 status code.

Is there a way to retrieve the original message inside the decoder. I can see that it is inside the FeignException, but not in the decode method. All I have is the 'status code' and a empty 'reason'.

public class CustomErrorDecoder implements ErrorDecoder {

    private final ErrorDecoder errorDecoder = new Default();

    @Override
    public Exception decode(String s, Response response) {

        switch (response.status()) {

            case 404:
                return new FileNotFoundException("File no found");
            case 403:
                return new ForbiddenAccessException("Forbidden access");
        }

        return errorDecoder.decode(s, response);
    }
}

Here the original message : "message":"Access to the file forbidden"

feign.FeignException: status 403 reading ProxyMicroserviceFiles#getUserRoot(); content:
{"timestamp":"2018-11-28T17:34:05.235+0000","status":403,"error":"Forbidden","message":"Access to the file forbidden","path":"/root"}

Also I use my FeignClient interface like a RestController so I don't use any other Controler populated with the proxy that could encapsulate the methods calls.

   @RestController
   @FeignClient(name = "zuul-server")
   @RibbonClient(name = "microservice-files")

   public interface ProxyMicroserviceFiles {

                @GetMapping(value = "microservice-files/root")
                Object getUserRoot();

                @GetMapping(value = "microservice-files/file/{id}")
                Object getFileById(@PathVariable("id") int id);

    }

Answer 1

Here is a solution, the message is actually in the response body as a stream.

package com.clientui.exceptions;

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.io.CharStreams;
import feign.Response;
import feign.codec.ErrorDecoder;
import lombok.*;

import java.io.*;

public class CustomErrorDecoder implements ErrorDecoder {

    private final ErrorDecoder errorDecoder = new Default();

    @Override
    public Exception decode(String s, Response response) {

        String message = null;
        Reader reader = null;

        try {
            reader = response.body().asReader();
            //Easy way to read the stream and get a String object
            String result = CharStreams.toString(reader);
            //use a Jackson ObjectMapper to convert the Json String into a 
            //Pojo
            ObjectMapper mapper = new ObjectMapper();
            //just in case you missed an attribute in the Pojo     
          mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
            //init the Pojo
            ExceptionMessage exceptionMessage = mapper.readValue(result, 
                                                ExceptionMessage.class);

            message = exceptionMessage.message;

        } catch (IOException e) {

            e.printStackTrace();
        }finally {

            //It is the responsibility of the caller to close the stream.
            try {

                if (reader != null)
                    reader.close();

            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        switch (response.status()) {

            case 404:
                return new FileNotFoundException(message == null ? "File no found" : 
                                                                     message);
            case 403:
                return new ForbiddenAccessException(message == null ? "Forbidden 
                                                              access" : message);

        }

        return errorDecoder.decode(s, response);
    }

    @Getter
    @Setter
    @NoArgsConstructor
    @AllArgsConstructor
    @ToString
    public static class ExceptionMessage{

        private String timestamp;
        private int status;
        private String error;
        private String message;
        private String path;

    }
}

Answer 2

If you want to get the response payload body, with the Feign exception, just use this method:

feignException.contentUTF8();

Example:

    try {
        itemResponse = call(); //method with the feign call
    } catch (FeignException e) {
        logger.error("ResponseBody: " + e.contentUTF8());
    }