Include generics on codecs

core/src/main/java/feign/Feign.java

@@ -103,8 +103,8 @@ public abstract class Feign {
     private Client client = new Client.Default(null, null);
     private Retryer retryer = new Retryer.Default();
     private Logger logger = new NoOpLogger();
-    private Encoder encoder = new Encoder.Default();
-    private Decoder decoder = new Decoder.Default();
+    private Encoder<?> encoder = new Encoder.Default();
+    private Decoder<?> decoder = new Decoder.Default();
     private QueryMapEncoder queryMapEncoder = new FieldQueryMapEncoder();
     private ErrorDecoder errorDecoder = new ErrorDecoder.Default();
     private Options options = new Options();
@@ -141,12 +141,12 @@ public abstract class Feign {
       return this;
     }
 
-    public Builder encoder(Encoder encoder) {
+    public <E> Builder encoder(Encoder<E> encoder) {
       this.encoder = encoder;
       return this;
     }
 
-    public Builder decoder(Decoder decoder) {
+    public <E> Builder decoder(Decoder<E> decoder) {
       this.decoder = decoder;
       return this;
     }
@@ -159,8 +159,8 @@ public abstract class Feign {
     /**
      * Allows to map the response before passing it to the decoder.
      */
-    public Builder mapAndDecode(ResponseMapper mapper, Decoder decoder) {
-      this.decoder = new ResponseMappingDecoder(mapper, decoder);
+    public <E> Builder mapAndDecode(ResponseMapper mapper, Decoder<E> decoder) {
+      this.decoder = new ResponseMappingDecoder<E>(mapper, decoder);
       return this;
     }
 
@@ -277,8 +277,8 @@ public abstract class Feign {
       Logger logger = Capability.enrich(this.logger, capabilities);
       Contract contract = Capability.enrich(this.contract, capabilities);
       Options options = Capability.enrich(this.options, capabilities);
-      Encoder encoder = Capability.enrich(this.encoder, capabilities);
-      Decoder decoder = Capability.enrich(this.decoder, capabilities);
+      Encoder<?> encoder = Capability.enrich(this.encoder, capabilities);
+      Decoder<?> decoder = Capability.enrich(this.decoder, capabilities);
       InvocationHandlerFactory invocationHandlerFactory =
           Capability.enrich(this.invocationHandlerFactory, capabilities);
       QueryMapEncoder queryMapEncoder = Capability.enrich(this.queryMapEncoder, capabilities);
@@ -293,18 +293,18 @@ public abstract class Feign {
     }
   }
 
-  public static class ResponseMappingDecoder implements Decoder {
+  public static class ResponseMappingDecoder<E> implements Decoder<E> {
 
     private final ResponseMapper mapper;
-    private final Decoder delegate;
+    private final Decoder<E> delegate;
 
-    public ResponseMappingDecoder(ResponseMapper mapper, Decoder decoder) {
+    public ResponseMappingDecoder(ResponseMapper mapper, Decoder<E> decoder) {
       this.mapper = mapper;
       this.delegate = decoder;
     }
 
     @Override
-    public Object decode(Response response, Type type) throws IOException {
+    public E decode(Response response, Type type) throws IOException {
       return delegate.decode(mapper.map(response, type), type);
     }
   }

core/src/main/java/feign/codec/Decoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -60,7 +60,7 @@ import feign.Util;
  * {@link DecodeException} unless they are a subclass of {@link FeignException} already, and unless
  * the client was configured with {@link Feign.Builder#decode404()}.
  */
-public interface Decoder {
+public interface Decoder<E> {
 
   /**
    * Decodes an http response into an object corresponding to its
@@ -75,10 +75,12 @@ public interface Decoder {
    * @throws DecodeException when decoding failed due to a checked exception besides IOException.
    * @throws FeignException when decoding succeeds, but conveys the operation failed.
    */
-  Object decode(Response response, Type type) throws IOException, DecodeException, FeignException;
+  E decode(Response response, Type type) throws IOException, DecodeException, FeignException;
 
   /** Default implementation of {@code Decoder}. */
-  public class Default extends StringDecoder {
+  public class Default implements Decoder<Object> {
+
+    private StringDecoder stringDecoder = new StringDecoder();
 
     @Override
     public Object decode(Response response, Type type) throws IOException {
@@ -89,7 +91,7 @@ public interface Decoder {
       if (byte[].class.equals(type)) {
         return Util.toByteArray(response.body().asInputStream());
       }
-      return super.decode(response, type);
+      return stringDecoder.decode(response, type);
     }
   }
 }

core/src/main/java/feign/codec/Encoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -63,7 +63,7 @@ import static java.lang.String.format;
  * Session login(@Param("username") String username, @Param("password") String password);
  * </pre>
  */
-public interface Encoder {
+public interface Encoder<E> {
   /** Type literal for {@code Map<String, ?>}, indicating the object to encode is a form. */
   Type MAP_STRING_WILDCARD = Util.MAP_STRING_WILDCARD;
 
@@ -76,12 +76,12 @@ public interface Encoder {
    * @param template the request template to populate.
    * @throws EncodeException when encoding failed due to a checked exception.
    */
-  void encode(Object object, Type bodyType, RequestTemplate template) throws EncodeException;
+  void encode(E object, Type bodyType, RequestTemplate template) throws EncodeException;
 
   /**
    * Default implementation of {@code Encoder}.
    */
-  class Default implements Encoder {
+  class Default implements Encoder<Object> {
 
     @Override
     public void encode(Object object, Type bodyType, RequestTemplate template) {

core/src/main/java/feign/codec/StringDecoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -19,10 +19,10 @@ import feign.Response;
 import feign.Util;
 import static java.lang.String.format;
 
-public class StringDecoder implements Decoder {
+public class StringDecoder implements Decoder<String> {
 
   @Override
-  public Object decode(Response response, Type type) throws IOException {
+  public String decode(Response response, Type type) throws IOException {
     Response.Body body = response.body();
     if (body == null) {
       return null;

core/src/main/java/feign/optionals/OptionalDecoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -22,19 +22,23 @@ import java.lang.reflect.Type;
 import java.util.Objects;
 import java.util.Optional;
 
-public final class OptionalDecoder implements Decoder {
-  final Decoder delegate;
+public final class OptionalDecoder<E> implements Decoder<E> {
+  final Decoder<E> delegate;
 
-  public OptionalDecoder(Decoder delegate) {
+  public OptionalDecoder(Decoder<E> delegate) {
     Objects.requireNonNull(delegate, "Decoder must not be null. ");
     this.delegate = delegate;
   }
 
   @Override
-  public Object decode(Response response, Type type) throws IOException {
+  public E decode(Response response, Type type) throws IOException {
     if (!isOptional(type)) {
       return delegate.decode(response, type);
     }
+    return (E) decodeOptional(response, type);
+  }
+
+  private Optional<E> decodeOptional(Response response, Type type) throws IOException {
     if (response.status() == 404 || response.status() == 204) {
       return Optional.empty();
     }

core/src/main/java/feign/stream/StreamDecoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -44,16 +44,16 @@ import static feign.Util.ensureClosed;
  * }</code>
  * </pre>
  */
-public final class StreamDecoder implements Decoder {
+public final class StreamDecoder<E> implements Decoder<Stream<E>> {
 
-  private final Decoder iteratorDecoder;
+  private final Decoder<E> iteratorDecoder;
 
-  StreamDecoder(Decoder iteratorDecoder) {
+  StreamDecoder(Decoder<E> iteratorDecoder) {
     this.iteratorDecoder = iteratorDecoder;
   }
 
   @Override
-  public Object decode(Response response, Type type)
+  public Stream<E> decode(Response response, Type type)
       throws IOException, FeignException {
     if (!(type instanceof ParameterizedType)) {
       throw new IllegalArgumentException("StreamDecoder supports only stream: unknown " + type);
@@ -62,7 +62,7 @@ public final class StreamDecoder implements Decoder {
     if (!Stream.class.equals(streamType.getRawType())) {
       throw new IllegalArgumentException("StreamDecoder supports only stream: unknown " + type);
     }
-    Iterator<?> iterator =
+    Iterator<E> iterator =
         (Iterator) iteratorDecoder.decode(response, new IteratorParameterizedType(streamType));
 
     return StreamSupport.stream(
@@ -76,8 +76,8 @@ public final class StreamDecoder implements Decoder {
         });
   }
 
-  public static StreamDecoder create(Decoder iteratorDecoder) {
-    return new StreamDecoder(iteratorDecoder);
+  public static <E> StreamDecoder<E> create(Decoder<E> iteratorDecoder) {
+    return new StreamDecoder<>(iteratorDecoder);
   }
 
   static final class IteratorParameterizedType implements ParameterizedType {

core/src/test/java/feign/AlwaysEncodeBodyContractTest.java

@@ -56,7 +56,7 @@ public class AlwaysEncodeBodyContractTest {
     String concatenate(String word1);
   }
 
-  private static class AllParametersSampleEncoder implements Encoder {
+  private static class AllParametersSampleEncoder implements Encoder<Object> {
     @Override
     public void encode(Object object, Type bodyType, RequestTemplate template)
         throws EncodeException {
@@ -67,7 +67,7 @@ public class AlwaysEncodeBodyContractTest {
     }
   }
 
-  private static class BodyParameterSampleEncoder implements Encoder {
+  private static class BodyParameterSampleEncoder implements Encoder<Object> {
     @Override
     public void encode(Object object, Type bodyType, RequestTemplate template)
         throws EncodeException {

core/src/test/java/feign/FeignTest.java

@@ -480,7 +480,7 @@ public class FeignTest {
     TestInterface api = new TestInterfaceBuilder()
         .decoder(new StringDecoder() {
           @Override
-          public Object decode(Response response, Type type) throws IOException {
+          public String decode(Response response, Type type) throws IOException {
             String string = super.decode(response, type).toString();
             if ("retry!".equals(string)) {
               throw new RetryableException(response.status(), string, HttpMethod.POST, null,

core/src/test/java/feign/UtilTest.java

@@ -298,7 +298,7 @@ public class UtilTest {
     ParameterizedDecoder<?> PARAMETERIZED_DECODER_UNBOUND = null;
   }
 
-  interface ParameterizedDecoder<T extends List<String>> extends Decoder {
+  interface ParameterizedDecoder<T extends List<String>> extends Decoder<Object> {
 
   }
 

core/src/test/java/feign/examples/GitHubExample.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -62,7 +62,7 @@ public class GitHubExample {
   /**
    * Here's how it looks to write a decoder. Note: you can instead use {@code feign-gson}!
    */
-  static class GsonDecoder implements Decoder {
+  static class GsonDecoder implements Decoder<Object> {
 
     private final Gson gson = new Gson();
 

dropwizard-metrics4/src/main/java/feign/metrics4/MeteredDecoder.java

@@ -27,14 +27,14 @@ import feign.codec.Decoder;
 /**
  * Warp feign {@link Decoder} with metrics.
  */
-public class MeteredDecoder implements Decoder {
+public class MeteredDecoder<E> implements Decoder<E> {
 
-  private final Decoder decoder;
+  private final Decoder<E> decoder;
   private final MetricRegistry metricRegistry;
   private final MetricSuppliers metricSuppliers;
   private final FeignMetricName metricName;
 
-  public MeteredDecoder(Decoder decoder, MetricRegistry metricRegistry,
+  public MeteredDecoder(Decoder<E> decoder, MetricRegistry metricRegistry,
       MetricSuppliers metricSuppliers) {
     this.decoder = decoder;
     this.metricRegistry = metricRegistry;
@@ -43,7 +43,7 @@ public class MeteredDecoder implements Decoder {
   }
 
   @Override
-  public Object decode(Response response, Type type)
+  public E decode(Response response, Type type)
       throws IOException, DecodeException, FeignException {
     final RequestTemplate template = response.request().requestTemplate();
     final MeteredBody body = response.body() == null
@@ -52,7 +52,7 @@ public class MeteredDecoder implements Decoder {
 
     response = response.toBuilder().body(body).build();
 
-    final Object decoded;
+    final E decoded;
     try (final Timer.Context classTimer =
         metricRegistry
             .timer(

dropwizard-metrics4/src/main/java/feign/metrics4/MeteredEncoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -24,14 +24,14 @@ import feign.codec.Encoder;
 /**
  * Warp feign {@link Encoder} with metrics.
  */
-public class MeteredEncoder implements Encoder {
+public class MeteredEncoder<E> implements Encoder<E> {
 
-  private final Encoder encoder;
+  private final Encoder<E> encoder;
   private final MetricRegistry metricRegistry;
   private final MetricSuppliers metricSuppliers;
   private final FeignMetricName metricName;
 
-  public MeteredEncoder(Encoder encoder, MetricRegistry metricRegistry,
+  public MeteredEncoder(Encoder<E> encoder, MetricRegistry metricRegistry,
       MetricSuppliers metricSuppliers) {
     this.encoder = encoder;
     this.metricRegistry = metricRegistry;
@@ -40,7 +40,7 @@ public class MeteredEncoder implements Encoder {
   }
 
   @Override
-  public void encode(Object object, Type bodyType, RequestTemplate template)
+  public void encode(E object, Type bodyType, RequestTemplate template)
       throws EncodeException {
     try (final Timer.Context classTimer =
         metricRegistry.timer(

dropwizard-metrics5/src/main/java/feign/metrics5/MeteredDecoder.java

@@ -25,16 +25,16 @@ import io.dropwizard.metrics5.MetricRegistry;
 import io.dropwizard.metrics5.Timer.Context;
 
 /**
- * Warp feign {@link Decoder} with metrics.
+ * Warp feign {@link Decoder<E>} with metrics.
  */
-public class MeteredDecoder implements Decoder {
+public class MeteredDecoder<E> implements Decoder<E> {
 
-  private final Decoder decoder;
+  private final Decoder<E> decoder;
   private final MetricRegistry metricRegistry;
   private final MetricSuppliers metricSuppliers;
   private final FeignMetricName metricName;
 
-  public MeteredDecoder(Decoder decoder, MetricRegistry metricRegistry,
+  public MeteredDecoder(Decoder<E> decoder, MetricRegistry metricRegistry,
       MetricSuppliers metricSuppliers) {
     this.decoder = decoder;
     this.metricRegistry = metricRegistry;
@@ -43,7 +43,7 @@ public class MeteredDecoder implements Decoder {
   }
 
   @Override
-  public Object decode(Response response, Type type)
+  public E decode(Response response, Type type)
       throws IOException, DecodeException, FeignException {
     final RequestTemplate template = response.request().requestTemplate();
     final MeteredBody body = response.body() == null
@@ -52,7 +52,7 @@ public class MeteredDecoder implements Decoder {
 
     response = response.toBuilder().body(body).build();
 
-    final Object decoded;
+    final E decoded;
     try (final Context classTimer =
         metricRegistry
             .timer(metricName.metricName(template.methodMetadata(), template.feignTarget())

dropwizard-metrics5/src/main/java/feign/metrics5/MeteredEncoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -24,14 +24,14 @@ import io.dropwizard.metrics5.Timer.Context;
 /**
  * Warp feign {@link Encoder} with metrics.
  */
-public class MeteredEncoder implements Encoder {
+public class MeteredEncoder<E> implements Encoder<E> {
 
-  private final Encoder encoder;
+  private final Encoder<E> encoder;
   private final MetricRegistry metricRegistry;
   private final MetricSuppliers metricSuppliers;
   private final FeignMetricName metricName;
 
-  public MeteredEncoder(Encoder encoder, MetricRegistry metricRegistry,
+  public MeteredEncoder(Encoder<E> encoder, MetricRegistry metricRegistry,
       MetricSuppliers metricSuppliers) {
     this.encoder = encoder;
     this.metricRegistry = metricRegistry;
@@ -40,7 +40,7 @@ public class MeteredEncoder implements Encoder {
   }
 
   @Override
-  public void encode(Object object, Type bodyType, RequestTemplate template)
+  public void encode(E object, Type bodyType, RequestTemplate template)
       throws EncodeException {
     try (final Context classTimer =
         metricRegistry.timer(

gson/src/main/java/feign/gson/GsonDecoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -25,7 +25,7 @@ import feign.codec.Decoder;
 import static feign.Util.UTF_8;
 import static feign.Util.ensureClosed;
 
-public class GsonDecoder implements Decoder {
+public class GsonDecoder implements Decoder<Object> {
 
   private final Gson gson;
 

gson/src/main/java/feign/gson/GsonEncoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -20,7 +20,7 @@ import java.util.Collections;
 import feign.RequestTemplate;
 import feign.codec.Encoder;
 
-public class GsonEncoder implements Encoder {
+public class GsonEncoder implements Encoder<Object> {
 
   private final Gson gson;
 

jackson-jaxb/src/main/java/feign/jackson/jaxb/JacksonJaxbJsonDecoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -23,7 +23,7 @@ import feign.codec.Decoder;
 import static com.fasterxml.jackson.jaxrs.json.JacksonJaxbJsonProvider.DEFAULT_ANNOTATIONS;
 import static javax.ws.rs.core.MediaType.APPLICATION_JSON_TYPE;
 
-public final class JacksonJaxbJsonDecoder implements Decoder {
+public final class JacksonJaxbJsonDecoder implements Decoder<Object> {
   private final JacksonJaxbJsonProvider jacksonJaxbJsonProvider;
 
   public JacksonJaxbJsonDecoder() {

jackson-jaxb/src/main/java/feign/jackson/jaxb/JacksonJaxbJsonEncoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -25,7 +25,7 @@ import feign.codec.Encoder;
 import static com.fasterxml.jackson.jaxrs.json.JacksonJaxbJsonProvider.DEFAULT_ANNOTATIONS;
 import static javax.ws.rs.core.MediaType.APPLICATION_JSON_TYPE;
 
-public final class JacksonJaxbJsonEncoder implements Encoder {
+public final class JacksonJaxbJsonEncoder implements Encoder<Object> {
   private final JacksonJaxbJsonProvider jacksonJaxbJsonProvider;
 
   public JacksonJaxbJsonEncoder() {

jackson-jr/src/main/java/feign/jackson/jr/JacksonJrDecoder.java

@@ -30,7 +30,7 @@ import java.util.Map;
 /**
  * A {@link Decoder} that uses Jackson Jr to convert objects to String or byte representation.
  */
-public class JacksonJrDecoder extends JacksonJrMapper implements Decoder {
+public class JacksonJrDecoder extends JacksonJrMapper implements Decoder<Object> {
 
   @FunctionalInterface
   interface Transformer {

jackson/src/main/java/feign/jackson/JacksonDecoder.java

@@ -28,7 +28,7 @@ import feign.Response;
 import feign.Util;
 import feign.codec.Decoder;
 
-public class JacksonDecoder implements Decoder {
+public class JacksonDecoder implements Decoder<Object> {
 
   private final ObjectMapper mapper;
 

jackson/src/main/java/feign/jackson/JacksonEncoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -26,7 +26,7 @@ import feign.codec.EncodeException;
 import feign.codec.Encoder;
 import feign.Util;
 
-public class JacksonEncoder implements Encoder {
+public class JacksonEncoder implements Encoder<Object> {
 
   private final ObjectMapper mapper;
 

jackson/src/main/java/feign/jackson/JacksonIteratorDecoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -54,7 +54,7 @@ import static feign.Util.ensureClosed;
  * }</code>
  * </pre>
  */
-public final class JacksonIteratorDecoder implements Decoder {
+public final class JacksonIteratorDecoder implements Decoder<Object> {
 
   private final ObjectMapper mapper;
 

jaxb/src/main/java/feign/jaxb/JAXBDecoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -47,7 +47,7 @@ import org.xml.sax.SAXException;
  * The JAXBContextFactory should be reused across requests as it caches the created JAXB contexts.
  * </p>
  */
-public class JAXBDecoder implements Decoder {
+public class JAXBDecoder implements Decoder<Object> {
 
   private final JAXBContextFactory jaxbContextFactory;
   private final boolean namespaceAware;

jaxb/src/main/java/feign/jaxb/JAXBEncoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -41,7 +41,7 @@ import feign.codec.Encoder;
  * The JAXBContextFactory should be reused across requests as it caches the created JAXB contexts.
  * </p>
  */
-public class JAXBEncoder implements Encoder {
+public class JAXBEncoder implements Encoder<Object> {
 
   private final JAXBContextFactory jaxbContextFactory;
 

json/src/main/java/feign/json/JsonDecoder.java

@@ -49,7 +49,7 @@ import static java.lang.String.format;
  *   System.out.println(contributors.getJSONObject(0).getString("login"));
  * </pre>
  */
-public class JsonDecoder implements Decoder {
+public class JsonDecoder implements Decoder<Object> {
 
   @Override
   public Object decode(Response response, Type type) throws IOException, DecodeException {

json/src/main/java/feign/json/JsonEncoder.java

@@ -48,7 +48,7 @@ import static java.lang.String.format;
  *   github.create("openfeign", "feign", contributor);
  * </pre>
  */
-public class JsonEncoder implements Encoder {
+public class JsonEncoder implements Encoder<Object> {
 
   @Override
   public void encode(Object object, Type bodyType, RequestTemplate template)

micrometer/src/main/java/feign/micrometer/MeteredDecoder.java

@@ -25,20 +25,20 @@ import java.util.Optional;
 import static feign.micrometer.MetricTagResolver.EMPTY_TAGS_ARRAY;
 
 /**
- * Warp feign {@link Decoder} with metrics.
+ * Warp feign {@link Decoder<E>} with metrics.
  */
-public class MeteredDecoder implements Decoder {
+public class MeteredDecoder<E> implements Decoder<E> {
 
-  private final Decoder decoder;
+  private final Decoder<E> decoder;
   private final MeterRegistry meterRegistry;
   private final MetricName metricName;
   private final MetricTagResolver metricTagResolver;
 
-  public MeteredDecoder(Decoder decoder, MeterRegistry meterRegistry) {
+  public MeteredDecoder(Decoder<E> decoder, MeterRegistry meterRegistry) {
     this(decoder, meterRegistry, new FeignMetricName(Decoder.class), new FeignMetricTagResolver());
   }
 
-  public MeteredDecoder(Decoder decoder, MeterRegistry meterRegistry, MetricName metricName,
+  public MeteredDecoder(Decoder<E> decoder, MeterRegistry meterRegistry, MetricName metricName,
       MetricTagResolver metricTagResolver) {
     this.decoder = decoder;
     this.meterRegistry = meterRegistry;
@@ -47,7 +47,7 @@ public class MeteredDecoder implements Decoder {
   }
 
   @Override
-  public Object decode(Response response, Type type)
+  public E decode(Response response, Type type)
       throws IOException, FeignException {
     final Optional<MeteredBody> body = Optional.ofNullable(response.body())
         .map(MeteredBody::new);
@@ -55,7 +55,7 @@ public class MeteredDecoder implements Decoder {
     Response meteredResponse = body.map(b -> response.toBuilder().body(b).build())
         .orElse(response);
 
-    Object decoded;
+    E decoded;
 
     final Timer.Sample sample = Timer.start(meterRegistry);
     Timer timer = null;

micrometer/src/main/java/feign/micrometer/MeteredEncoder.java

@@ -23,18 +23,18 @@ import static feign.micrometer.MetricTagResolver.EMPTY_TAGS_ARRAY;
 /**
  * Warp feign {@link Encoder} with metrics.
  */
-public class MeteredEncoder implements Encoder {
+public class MeteredEncoder<E> implements Encoder<E> {
 
-  private final Encoder encoder;
+  private final Encoder<E> encoder;
   private final MeterRegistry meterRegistry;
   private final MetricName metricName;
   private final MetricTagResolver metricTagResolver;
 
-  public MeteredEncoder(Encoder encoder, MeterRegistry meterRegistry) {
+  public MeteredEncoder(Encoder<E> encoder, MeterRegistry meterRegistry) {
     this(encoder, meterRegistry, new FeignMetricName(Encoder.class), new FeignMetricTagResolver());
   }
 
-  public MeteredEncoder(Encoder encoder,
+  public MeteredEncoder(Encoder<E> encoder,
       MeterRegistry meterRegistry,
       MetricName metricName,
       MetricTagResolver metricTagResolver) {
@@ -45,7 +45,7 @@ public class MeteredEncoder implements Encoder {
   }
 
   @Override
-  public void encode(Object object, Type bodyType, RequestTemplate template)
+  public void encode(E object, Type bodyType, RequestTemplate template)
       throws EncodeException {
     createTimer(object, bodyType, template)
         .record(() -> encoder.encode(object, bodyType, template));

mock/src/test/java/feign/mock/MockClientSequentialTest.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -72,16 +72,16 @@ public class MockClientSequentialTest {
 
   }
 
-  class AssertionDecoder implements Decoder {
+  class AssertionDecoder<E> implements Decoder<E> {
 
-    private final Decoder delegate;
+    private final Decoder<E> delegate;
 
-    public AssertionDecoder(Decoder delegate) {
+    public AssertionDecoder(Decoder<E> delegate) {
       this.delegate = delegate;
     }
 
     @Override
-    public Object decode(Response response, Type type)
+    public E decode(Response response, Type type)
         throws IOException, DecodeException, FeignException {
       assertThat(response.request(), notNullValue());
 
@@ -102,7 +102,7 @@ public class MockClientSequentialTest {
           .add("Name", "netflix")
           .build();
       mockClientSequential = new MockClient(true);
-      githubSequential = Feign.builder().decoder(new AssertionDecoder(new GsonDecoder()))
+      githubSequential = Feign.builder().decoder(new AssertionDecoder<>(new GsonDecoder()))
           .client(mockClientSequential
               .add(RequestKey
                   .builder(HttpMethod.GET, "/repos/netflix/feign/contributors")

mock/src/test/java/feign/mock/MockClientTest.java

@@ -68,16 +68,16 @@ public class MockClientTest {
 
   }
 
-  class AssertionDecoder implements Decoder {
+  class AssertionDecoder<E> implements Decoder<E> {
 
-    private final Decoder delegate;
+    private final Decoder<E> delegate;
 
-    public AssertionDecoder(Decoder delegate) {
+    public AssertionDecoder(Decoder<E> delegate) {
       this.delegate = delegate;
     }
 
     @Override
-    public Object decode(Response response, Type type)
+    public E decode(Response response, Type type)
         throws IOException, DecodeException, FeignException {
       assertThat(response.request(), notNullValue());
 
@@ -103,7 +103,7 @@ public class MockClientTest {
               .body("{\"login\":\"velo_at_github\",\"type\":\"preposterous hacker\"}")
               .build();
       mockClient = new MockClient();
-      github = Feign.builder().decoder(new AssertionDecoder(new GsonDecoder()))
+      github = Feign.builder().decoder(new AssertionDecoder<>(new GsonDecoder()))
           .client(mockClient.ok(HttpMethod.GET, "/repos/netflix/feign/contributors", data)
               .ok(HttpMethod.GET, "/repos/netflix/feign/contributors?client_id=55")
               .ok(HttpMethod.GET, "/repos/netflix/feign/contributors?client_id=7 7",

sax/src/main/java/feign/sax/SAXDecoder.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2012-2020 The Feign Authors
+ * Copyright 2012-2021 The Feign Authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -46,7 +46,7 @@ import static feign.Util.resolveLastTypeParameter;
  *     .target(MyApi.class, "http://api");
  * </pre>
  */
-public class SAXDecoder implements Decoder {
+public class SAXDecoder implements Decoder<Object> {
 
   private final Map<Type, ContentHandlerWithResult.Factory<?>> handlerFactories;
 

soap/src/main/java/feign/soap/SOAPDecoder.java

@@ -81,7 +81,7 @@ import feign.jaxb.JAXBContextFactory;
  * @see SOAPErrorDecoder
  * @see SOAPFaultException
  */
-public class SOAPDecoder implements Decoder {
+public class SOAPDecoder implements Decoder<Object> {
 
 
   private final JAXBContextFactory jaxbContextFactory;

soap/src/main/java/feign/soap/SOAPEncoder.java

@@ -83,7 +83,7 @@ import feign.jaxb.JAXBContextFactory;
  * The JAXBContextFactory should be reused across requests as it caches the created JAXB contexts.
  * </p>
  */
-public class SOAPEncoder implements Encoder {
+public class SOAPEncoder implements Encoder<Object> {
 
   private static final String DEFAULT_SOAP_PROTOCOL = SOAPConstants.SOAP_1_1_PROTOCOL;