Add Moshi (#2182)

* Add Moshi

* Update README.md

---------

Co-authored-by: Vikramaditya Chhapwale <cvikramad@gmail.com>

README.md

@@ -409,6 +409,17 @@ public class Example {
 For the lighter weight Jackson Jr, use `JacksonJrEncoder` and `JacksonJrDecoder` from
 the [Jackson Jr Module](./jackson-jr).
 
+#### Moshi
+[Moshi](./moshi) includes an encoder and decoder you can use with a JSON API.
+Add `MoshiEncoder` and/or `MoshiDecoder` to your `Feign.Builder` like so:
+
+```java
+GitHub github = Feign.builder()
+                     .encoder(new MoshiEncoder())
+                     .decoder(new MoshiDecoder())
+                     .target(GitHub.class, "https://api.github.com");
+```
+
 #### Sax
 [SaxDecoder](./sax) allows you to decode XML in a way that is compatible with normal JVM and also Android environments.
 

moshi/README.md

@@ -0,0 +1,13 @@
+Moshi Codec
+===================
+
+This module adds support for encoding and decoding JSON via the Moshi library.
+
+Add `MoshiEncoder` and/or `MoshiDecoder` to your `Feign.Builder` like so:
+
+```java
+GitHub github = Feign.builder()
+                     .encoder(new MoshiEncoder())
+                     .decoder(new MoshiDecoder())
+                     .target(GitHub.class, "https://api.github.com");
+```

moshi/pom.xml

@@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Copyright 2012-2023 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
+
+    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.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>io.github.openfeign</groupId>
+    <artifactId>parent</artifactId>
+    <version>13.0-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>feign-moshi</artifactId>
+  <name>Feign Moshi</name>
+  <description>Feign Moshi</description>
+
+  <properties>
+    <main.basedir>${project.basedir}/..</main.basedir>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>feign-core</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>com.squareup.moshi</groupId>
+      <artifactId>moshi</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>com.google.guava</groupId>
+      <artifactId>guava</artifactId>
+      <version>${guava.version}</version>
+    </dependency>
+
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>feign-core</artifactId>
+      <type>test-jar</type>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>

moshi/src/main/java/feign/moshi/MoshiDecoder.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2012-2023 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
+ *
+ * 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.moshi;
+
+import static feign.Util.UTF_8;
+import static feign.Util.ensureClosed;
+
+import com.google.common.io.CharStreams;
+import com.squareup.moshi.JsonAdapter;
+import com.squareup.moshi.JsonDataException;
+import com.squareup.moshi.Moshi;
+import feign.Response;
+import feign.Util;
+import feign.codec.Decoder;
+import java.io.IOException;
+import java.io.Reader;
+import java.lang.reflect.Type;
+
+public class MoshiDecoder implements Decoder {
+  private final Moshi moshi;
+
+  public MoshiDecoder(Moshi moshi) {
+    this.moshi = moshi;
+  }
+
+  public MoshiDecoder() {
+    this.moshi = new Moshi.Builder().build();
+  }
+
+  public MoshiDecoder(Iterable<JsonAdapter<?>> adapters) {
+    this(MoshiFactory.create(adapters));
+  }
+
+  @Override
+  public Object decode(Response response, Type type) throws IOException {
+    JsonAdapter<Object> jsonAdapter = moshi.adapter(type);
+
+    if (response.status() == 404 || response.status() == 204) return Util.emptyValueOf(type);
+    if (response.body() == null) return null;
+
+    Reader reader = response.body().asReader(UTF_8);
+
+    try {
+      return parseJson(jsonAdapter, reader);
+    } catch (JsonDataException e) {
+      if (e.getCause() != null && e.getCause() instanceof IOException) {
+        throw (IOException) e.getCause();
+      }
+      throw e;
+    } finally {
+      ensureClosed(reader);
+    }
+  }
+
+  private Object parseJson(JsonAdapter<Object> jsonAdapter, Reader reader) throws IOException {
+    String targetString = CharStreams.toString(reader);
+    return jsonAdapter.fromJson(targetString);
+  }
+}

moshi/src/main/java/feign/moshi/MoshiEncoder.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2012-2023 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
+ *
+ * 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.moshi;
+
+import com.squareup.moshi.JsonAdapter;
+import com.squareup.moshi.Moshi;
+import feign.RequestTemplate;
+import feign.codec.Encoder;
+import java.lang.reflect.Type;
+
+public class MoshiEncoder implements Encoder {
+
+  private final Moshi moshi;
+
+  public MoshiEncoder() {
+    this.moshi = new Moshi.Builder().build();
+  }
+
+  public MoshiEncoder(Moshi moshi) {
+    this.moshi = moshi;
+  }
+
+  public MoshiEncoder(Iterable<JsonAdapter<?>> adapters) {
+    this(MoshiFactory.create(adapters));
+  }
+
+  @Override
+  public void encode(Object object, Type bodyType, RequestTemplate template) {
+    JsonAdapter<Object> jsonAdapter = moshi.adapter(bodyType).indent("  ");
+    template.body(jsonAdapter.toJson(object));
+  }
+}

moshi/src/main/java/feign/moshi/MoshiFactory.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2012-2023 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
+ *
+ * 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.moshi;
+
+import com.squareup.moshi.JsonAdapter;
+import com.squareup.moshi.Moshi;
+
+public class MoshiFactory {
+  private MoshiFactory() {}
+
+  /**
+   * Registers JsonAdapter by implicit type. Adds one to read numbers in a {@code Map<String,
+   * Object>} as Integers.
+   */
+  static Moshi create(Iterable<JsonAdapter<?>> adapters) {
+    Moshi.Builder builder = new Moshi.Builder();
+
+    for (JsonAdapter<?> adapter : adapters) {
+      builder.add(adapter.getClass(), adapter);
+    }
+
+    return builder.build();
+  }
+}