feign.codec

Interface Decoder

All Known Implementing Classes:

Decoder.Default, Feign.ResponseMappingDecoder, OptionalDecoder, StreamDecoder, StringDecoder

public interface Decoder

Decodes an HTTP response into a single object of the given type. Invoked when Response.status() is in the 2xx range and the return type is neither void nor Response.

Example Implementation:

 public class GsonDecoder implements Decoder {
   private final Gson gson = new Gson();

   @Override
   public Object decode(Response response, Type type) throws IOException {
     try {
       return gson.fromJson(response.body().asReader(), type);
     } catch (JsonIOException e) {
       if (e.getCause() != null &&
           e.getCause() instanceof IOException) {
         throw IOException.class.cast(e.getCause());
       }
       throw e;
     }
   }
 }
 

Implementation Note

The type parameter will correspond to the generic return type of an interface processed by Feign.newInstance(feign.Target). When writing your implementation of Decoder, ensure you also test parameterized types such as List<Foo>.

Note on exception propagation

Exceptions thrown by Decoders get wrapped in a DecodeException unless they are a subclass of FeignException already, and unless the client was configured with Feign.Builder#dismiss404().

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	Decoder.Default Default implementation of Decoder.

Method Summary

Modifier and Type	Method and Description
Object	decode(Response response, Type type) Decodes an http response into an object corresponding to its generic return type.

Method Detail

decode

Object decode(Response response,
              Type type)
       throws IOException,
              DecodeException,
              FeignException

Decodes an http response into an object corresponding to its generic return type. If you need to wrap exceptions, please do so via DecodeException.

Parameters:

response - the response to decode

type - generic return type of the method corresponding to this response.

Returns:

instance of type

Throws:

IOException - will be propagated safely to the caller.

DecodeException - when decoding failed due to a checked exception besides IOException.

FeignException - when decoding succeeds, but conveys the operation failed.