ProtoConverterFactory.java

/*
 * Copyright (C) 2013 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 retrofit2.converter.protobuf;

import com.google.protobuf.ExtensionRegistryLite;
import com.google.protobuf.MessageLite;
import com.google.protobuf.Parser;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import javax.annotation.Nullable;
import okhttp3.RequestBody;
import okhttp3.ResponseBody;
import retrofit2.Converter;
import retrofit2.Retrofit;

/**
 * A {@linkplain Converter.Factory converter} which uses Protocol Buffers.
 * <p>
 * This converter only applies for types which extend from {@link MessageLite} (or one of its
 * subclasses).
 */
public final class ProtoConverterFactory extends Converter.Factory {
  public static ProtoConverterFactory create() {
    return new ProtoConverterFactory(null);
  }

  /** Create an instance which uses {@code registry} when deserializing. */
  public static ProtoConverterFactory createWithRegistry(@Nullable ExtensionRegistryLite registry) {
    return new ProtoConverterFactory(registry);
  }

  private final @Nullable ExtensionRegistryLite registry;

  private ProtoConverterFactory(@Nullable ExtensionRegistryLite registry) {
    this.registry = registry;
  }

  @Override
  public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations,
      Retrofit retrofit) {
    if (!(type instanceof Class<?>)) {
      return null;
    }
    Class<?> c = (Class<?>) type;
    if (!MessageLite.class.isAssignableFrom(c)) {
      return null;
    }

    Parser<MessageLite> parser;
    try {
      Method method = c.getDeclaredMethod("parser");
      //noinspection unchecked
      parser = (Parser<MessageLite>) method.invoke(null);
    } catch (InvocationTargetException e) {
      throw new RuntimeException(e.getCause());
    } catch (NoSuchMethodException | IllegalAccessException ignored) {
      // If the method is missing, fall back to original static field for pre-3.0 support.
      try {
        Field field = c.getDeclaredField("PARSER");
        //noinspection unchecked
        parser = (Parser<MessageLite>) field.get(null);
      } catch (NoSuchFieldException | IllegalAccessException e) {
        throw new IllegalArgumentException("Found a protobuf message but "
            + c.getName()
            + " had no parser() method or PARSER field.");
      }
    }
    return new ProtoResponseBodyConverter<>(parser, registry);
  }

  @Override
  public Converter<?, RequestBody> requestBodyConverter(Type type,
      Annotation[] parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {
    if (!(type instanceof Class<?>)) {
      return null;
    }
    if (!MessageLite.class.isAssignableFrom((Class<?>) type)) {
      return null;
    }
    return new ProtoRequestBodyConverter<>();
  }
}