Merge pull request #1541 from square/jw/annotation-delegation

Add sample showing converter delegation via annotations.

samples/pom.xml

@@ -29,6 +29,11 @@
       <artifactId>converter-gson</artifactId>
       <version>${project.version}</version>
     </dependency>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>converter-simplexml</artifactId>
+      <version>${project.version}</version>
+    </dependency>
     <dependency>
       <groupId>com.squareup.okhttp3</groupId>
       <artifactId>mockwebserver</artifactId>

samples/src/main/java/com/example/retrofit/JsonAndXmlConverters.java

+/*
+ * Copyright (C) 2016 Square, 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 com.example.retrofit;
+
+import java.io.IOException;
+import java.lang.annotation.Annotation;
+import java.lang.annotation.Retention;
+import java.lang.reflect.Type;
+import okhttp3.RequestBody;
+import okhttp3.ResponseBody;
+import okhttp3.mockwebserver.MockResponse;
+import okhttp3.mockwebserver.MockWebServer;
+import org.simpleframework.xml.Attribute;
+import org.simpleframework.xml.Default;
+import org.simpleframework.xml.DefaultType;
+import retrofit2.Call;
+import retrofit2.Converter;
+import retrofit2.Retrofit;
+import retrofit2.converter.gson.GsonConverterFactory;
+import retrofit2.converter.simplexml.SimpleXmlConverterFactory;
+import retrofit2.http.GET;
+
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+/**
+ * Both the Gson converter and the Simple Framework converter accept all types. Because of this,
+ * you cannot use both in a single service by default. In order to work around this, we can create
+ * an @Json and @Xml annotation to declare which serialization format each endpoint should use and
+ * then write our own Converter.Factory which delegates to either the Gson or Simple Framework
+ * converter.
+ */
+public final class JsonAndXmlConverters {
+  @Retention(RUNTIME)
+  @interface Json {
+  }
+
+  @Retention(RUNTIME)
+  @interface Xml {
+  }
+
+  static class QualifiedTypeConverterFactory extends Converter.Factory {
+    private final Converter.Factory jsonFactory;
+    private final Converter.Factory xmlFactory;
+
+    QualifiedTypeConverterFactory(Converter.Factory jsonFactory, Converter.Factory xmlFactory) {
+      this.jsonFactory = jsonFactory;
+      this.xmlFactory = xmlFactory;
+    }
+
+    @Override
+    public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations,
+        Retrofit retrofit) {
+      for (Annotation annotation : annotations) {
+        if (annotation instanceof Json) {
+          return jsonFactory.responseBodyConverter(type, annotations, retrofit);
+        }
+        if (annotation instanceof Xml) {
+          return xmlFactory.responseBodyConverter(type, annotations, retrofit);
+        }
+      }
+      return null;
+    }
+
+    @Override
+    public Converter<?, RequestBody> requestBodyConverter(Type type, Annotation[] annotations,
+        Retrofit retrofit) {
+      for (Annotation annotation : annotations) {
+        if (annotation instanceof Json) {
+          return jsonFactory.requestBodyConverter(type, annotations, retrofit);
+        }
+        if (annotation instanceof Xml) {
+          return jsonFactory.requestBodyConverter(type, annotations, retrofit);
+        }
+      }
+      return null;
+    }
+  }
+
+  @Default(value = DefaultType.FIELD)
+  static class User {
+    @Attribute
+    public String name;
+  }
+
+  interface Service {
+    @GET("/") @Json
+    Call<User> exampleJson();
+    @GET("/") @Xml
+    Call<User> exampleXml();
+  }
+
+  public static void main(String... args) throws IOException {
+    MockWebServer server = new MockWebServer();
+    server.start();
+    server.enqueue(new MockResponse().setBody("{\"name\": \"Jason\"}"));
+    server.enqueue(new MockResponse().setBody("<user name=\"Eximel\"/>"));
+
+    Retrofit retrofit = new Retrofit.Builder()
+        .baseUrl(server.url("/"))
+        .addConverterFactory(new QualifiedTypeConverterFactory(
+            GsonConverterFactory.create(),
+            SimpleXmlConverterFactory.create()))
+        .build();
+    Service service = retrofit.create(Service.class);
+
+    User user1 = service.exampleJson().execute().body();
+    System.out.println("User 1: " + user1.name);
+
+    User user2 = service.exampleXml().execute().body();
+    System.out.println("User 2: " + user2.name);
+
+    server.shutdown();
+  }
+}