OpenFeign · matthurne · Oct 15, 2013 · davidmc24 · Oct 8, 2013 · codefromthecrypt
diff --git a/CHANGES.md b/CHANGES.md
@@ -1,5 +1,6 @@
 ### Version 5.4.0
 * Add `BasicAuthRequestInterceptor`
+* Add Jackson integration
 
 ### Version 5.3.0
 * Split `GsonCodec` into `GsonEncoder` and `GsonDecoder`, which are easy to use with `Feign.Builder`

diff --git a/README.md b/README.md
@@ -99,6 +99,18 @@ GitHub github = Feign.builder()
                      .target(GitHub.class, "https://api.github.com");
 ```
 
+### Jackson
+[JacksonModule](https://github.com/Netflix/feign/tree/master/jackson) adds an encoder and decoder you can use with a JSON API.
+
+Add `JacksonEncoder` and/or `JacksonDecoder` to your `Feign.Builder` like so:
+
+```java
+GitHub github = Feign.builder()
+                     .encoder(new JacksonEncoder())
+                     .decoder(new JacksonDecoder())
+                     .target(GitHub.class, "https://api.github.com");
+```
+
 ### Sax
 [SaxDecoder](https://github.com/Netflix/feign/tree/master/sax) allows you to decode XML in a way that is compatible with normal JVM and also Android environments.
 

diff --git a/build.gradle b/build.gradle
@@ -73,6 +73,21 @@ project(':feign-gson') {
     }
 }
 
+project(':feign-jackson') {
+    apply plugin: 'java'
+
+    test {
+        useTestNG()
+    }
+
+    dependencies {
+        compile     project(':feign-core')
+        compile     'com.fasterxml.jackson.core:jackson-databind:2.2.2'
+        testCompile 'org.testng:testng:6.8.5'
+        testCompile 'com.google.guava:guava:14.0.1'
+    }
+}
+
 project(':feign-jaxrs') {
     apply plugin: 'java'
 

diff --git a/core/src/main/java/feign/codec/DecodeException.java b/core/src/main/java/feign/codec/DecodeException.java
@@ -22,7 +22,7 @@
 /**
  * Similar to {@code javax.websocket.DecodeException}, raised when a problem
  * occurs decoding a message.  Note that {@code DecodeException} is not an
- * {@code IOException}, nor have one set as its cause.
+ * {@code IOException}, nor does it have one set as its cause.
  */
 public class DecodeException extends FeignException {
 

diff --git a/core/src/main/java/feign/codec/EncodeException.java b/core/src/main/java/feign/codec/EncodeException.java
@@ -21,8 +21,8 @@
 
 /**
  * Similar to {@code javax.websocket.EncodeException}, raised when a problem
- * occurs decoding a message.  Note that {@code DecodeException} is not an
- * {@code IOException}, nor have one set as its cause.
+ * occurs encoding a message.  Note that {@code EncodeException} is not an
+ * {@code IOException}, nor does it have one set as its cause.
  */
 public class EncodeException extends FeignException {
 

diff --git a/jackson/README.md b/jackson/README.md
@@ -0,0 +1,33 @@
+Jackson Codec
+===================
+
+This module adds support for encoding and decoding JSON via Jackson.
+
+Add `JacksonEncoder` and/or `JacksonDecoder` to your `Feign.Builder` like so:
+
+```java
+GitHub github = Feign.builder()
+                     .encoder(new JacksonEncoder())
+                     .decoder(new JacksonDecoder())
+                     .target(GitHub.class, "https://api.github.com");
+```
+
+If you want to customize the `ObjectMapper` that is used, provide it to the `JacksonEncoder` and `JacksonDecoder`:
+
+```java
+ObjectMapper mapper = new ObjectMapper()
+        .setSerializationInclusion(JsonInclude.Include.NON_NULL)
+        .configure(SerializationFeature.INDENT_OUTPUT, true)
+        .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
+
+GitHub github = Feign.builder()
+                     .encoder(new JacksonEncoder(mapper))
+                     .decoder(new JacksonDecoder(mapper))
+                     .target(GitHub.class, "https://api.github.com");
+```
+
+Alternatively, you can add the encoder and decoder to your Dagger object graph using the provided `JacksonModule` like so:
+
+```java
+GitHub github = Feign.create(GitHub.class, "https://api.github.com", new JacksonModule());
+```
diff --git a/jackson/src/main/java/feign/jackson/JacksonDecoder.java b/jackson/src/main/java/feign/jackson/JacksonDecoder.java
@@ -0,0 +1,53 @@
+/*
+ * Copyright 2013 Netflix, Inc.
+ *
+ * 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package feign.jackson;
+
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.RuntimeJsonMappingException;
+import feign.Response;
+import feign.codec.Decoder;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.lang.reflect.Type;
+
+public class JacksonDecoder implements Decoder {
+  private final ObjectMapper mapper;
+
+  public JacksonDecoder() {
+    this(new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false));
+  }
+
+  public JacksonDecoder(ObjectMapper mapper) {
+    this.mapper = mapper;
+  }
+
+  @Override public Object decode(Response response, Type type) throws IOException {
+    if (response.body() == null) {
+      return null;
+    }
+    Reader reader = response.body().asReader();
+    try {
+      return mapper.readValue(reader, mapper.constructType(type));
+    } catch (RuntimeJsonMappingException e) {
+      if (e.getCause() != null && e.getCause() instanceof IOException) {
+        throw IOException.class.cast(e.getCause());
+      }
+      throw e;
+    }
+  }
+}
diff --git a/jackson/src/main/java/feign/jackson/JacksonEncoder.java b/jackson/src/main/java/feign/jackson/JacksonEncoder.java
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2013 Netflix, Inc.
+ *
+ * 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package feign.jackson;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import feign.RequestTemplate;
+import feign.codec.EncodeException;
+import feign.codec.Encoder;
+
+public class JacksonEncoder implements Encoder {
+  private final ObjectMapper mapper;
+
+  public JacksonEncoder() {
+    this(new ObjectMapper()
+        .setSerializationInclusion(JsonInclude.Include.NON_NULL)
+        .configure(SerializationFeature.INDENT_OUTPUT, true));
+  }
+
+  public JacksonEncoder(ObjectMapper mapper) {
+    this.mapper = mapper;
+  }
+
+  @Override public void encode(Object object, RequestTemplate template) throws EncodeException {
+    try {
+      template.body(mapper.writeValueAsString(object));
+    } catch (JsonProcessingException e) {
+      throw new EncodeException(e.getMessage(), e);
+    }
+  }
+}
diff --git a/jackson/src/main/java/feign/jackson/JacksonModule.java b/jackson/src/main/java/feign/jackson/JacksonModule.java
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2013 Netflix, Inc.
+ *
+ * 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package feign.jackson;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.Module;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import dagger.Provides;
+import feign.Feign;
+import feign.codec.Decoder;
+import feign.codec.Encoder;
+
+import javax.inject.Singleton;
+import java.util.Collections;
+import java.util.Set;
+
+/**
+ * <h3>Custom serializers/deserializers</h3>
+ * <br>
+ * In order to specify custom json parsing, Jackson's {@code ObjectMapper} supports {@link JsonSerializer serializers}
+ * and {@link JsonDeserializer deserializers}, which can be bundled together in {@link Module modules}.
+ * <p/>
+ * <br>
+ * Here's an example of adding a custom module.
+ * <p/>
+ * <pre>
+ * public class ObjectIdSerializer extends StdSerializer&lt;ObjectId&gt; {
+ *     public ObjectIdSerializer() {
+ *         super(ObjectId.class);
+ *     }
+ *
+ *     &#064;Override
+ *     public void serialize(ObjectId value, JsonGenerator jsonGenerator, SerializerProvider provider) throws IOException {
+ *         jsonGenerator.writeString(value.toString());
+ *     }
+ * }
+ *
+ * public class ObjectIdDeserializer extends StdDeserializer&lt;ObjectId&gt; {
+ *     public ObjectIdDeserializer() {
+ *         super(ObjectId.class);
+ *     }
+ *
+ *     &#064;Override
+ *     public ObjectId deserialize(JsonParser jsonParser, DeserializationContext context) throws IOException {
+ *         return ObjectId.massageToObjectId(jsonParser.getValueAsString());
+ *     }
+ * }
+ *
+ * public class ObjectIdModule extends SimpleModule {
+ *     public ObjectIdModule() {
+ *         // first deserializers
+ *         addDeserializer(ObjectId.class, new ObjectIdDeserializer());
+ *
+ *         // then serializers:
+ *         addSerializer(ObjectId.class, new ObjectIdSerializer());
+ *     }
+ * }
+ *
+ * &#064;Provides(type = Provides.Type.SET)
+ * Module objectIdModule() {
+ *     return new ObjectIdModule();
+ * }
+ * </pre>
+ */
+@dagger.Module(injects = Feign.class, addsTo = Feign.Defaults.class)
+public final class JacksonModule {
+  @Provides Encoder encoder(ObjectMapper mapper) {
+    return new JacksonEncoder(mapper);
+  }
+
+  @Provides Decoder decoder(ObjectMapper mapper) {
+    return new JacksonDecoder(mapper);
+  }
+
+  @Provides @Singleton ObjectMapper mapper(Set<Module> modules) {
+    return new ObjectMapper()
+        .setSerializationInclusion(JsonInclude.Include.NON_NULL)
+        .configure(SerializationFeature.INDENT_OUTPUT, true)
+        .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
+        .registerModules(modules);
+  }
+
+  @Provides(type = Provides.Type.SET_VALUES) Set<Module> noDefaultModules() {
+    return Collections.emptySet();
+  }
+}