Feign ErrorDecoder ：检索原始消息

Question

我使用 ErrorDecoder 返回正确的异常而不是 500 状态代码。

有没有办法在解码器中检索原始消息。我可以看到它在 FeignException 内部，但不在 decode 方法中。我只有“状态代码”和一个空的“原因”。

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);
    }
}

这里是原始消息：“消息”：“禁止访问文件”

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"}

我还使用我的 FeignClient 接口，如 RestController，因此我不使用任何其他填充了可以封装方法调用的代理的控制器。

   @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

这里有一个解决方案，消息实际上是在响应体中作为一个流。

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

如果你和我一样，真的只是想从失败的 Feign 调用中获得内容，而无需所有这些自定义解码器和样板，那么有一种很老套的方法来做到这一点。

如果我们在创建 FeignException 并且存在响应主体时查看它，它会像这样组装异常消息：

if (response.body() != null) {
    String body = Util.toString(response.body().asReader());
    message += "; content:\n" + body;
}

因此，如果您在响应正文之后，您可以通过解析异常消息将其拉出，因为它由换行符分隔。

String[] feignExceptionMessageParts = e.getMessage().split("\n");
String responseContent = feignExceptionMessageParts[1];

如果你想要这个对象，你可以使用 Jackson 之类的东西：

MyResponseBodyPojo errorBody = objectMapper.readValue(responseContent, MyResponseBodyPojo.class);

我并不认为这是一种聪明的方法或最佳实践。

Answer 3

如果你想得到response payload body，除了Feign异常，使用这个方法即可：

feignException.contentUTF8();

例子：

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

Answer 4

原始消息在响应正文中，正如已经回答的那样。但是，我们可以使用 Java 8 Streams 来减少样板的数量：

public class CustomErrorDecoder implements ErrorDecoder {

  private final ErrorDecoder errorDecoder = new Default();

  @Override
  public Exception decode(String s, Response response) {
    String body = "4xx client error";
    try {
        body = new BufferedReader(response.body().asReader(StandardCharsets.UTF_8))
          .lines()
          .collect(Collectors.joining("\n"));
    } catch (IOException ignore) {}

    switch (response.status()) {

        case 404:
            return new FileNotFoundException(body);
        case 403:
            return new ForbiddenAccessException(body);
    }

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

Answer 5

建议使用输入流代替阅读器并将其映射到您的对象。

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;
        InputStream responseBodyIs = null;
        try {
            responseBodyIs = response.body().asInputStream();
            ObjectMapper mapper = new ObjectMapper();
            ExceptionMessage exceptionMessage = mapper.readValue(responseBodyIs, ExceptionMessage.class);

            message = exceptionMessage.message;

        } catch (IOException e) {

            e.printStackTrace();
            // you could also return an exception
            return new errorMessageFormatException(e.getMessage());
        }finally {

            //It is the responsibility of the caller to close the stream.
            try {
                if (responseBodyIs != null)
                    responseBodyIs.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 6

接受答案的一些重构和代码风格：

@Override
@SneakyThrows
public Exception decode(String methodKey, Response response) {
  String message;

  try (Reader reader = response.body().asReader()) {
    String result = StringUtils.toString(reader);
    message = mapper.readValue(result, ErrorResponse.class).getMessage();
  }

  if (response.status() == 401) {
    return new UnauthorizedException(message == null ? response.reason() : message);
  }
  if (response.status() == 403) {
    return new ForbiddenException(message == null ? response.reason() : message);
  }
  return defaultErrorDecoder.decode(methodKey, response);
}