GuavaOptionalConverterFactory.java

/*
 * Copyright (C) 2017 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 retrofit.converter.guava;

import com.google.common.base.Optional;
import java.lang.annotation.Annotation;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import javax.annotation.Nullable;
import okhttp3.ResponseBody;
import retrofit2.Converter;
import retrofit2.Retrofit;

/**
 * A {@linkplain Converter.Factory converter} for {@code Optional<T>} which delegates to another
 * converter to deserialize {@code T} and then wraps it into {@link Optional}.
 */
public final class GuavaOptionalConverterFactory extends Converter.Factory {
  public static GuavaOptionalConverterFactory create() {
    return new GuavaOptionalConverterFactory();
  }

  private GuavaOptionalConverterFactory() {
  }

  @Nullable @Override
  public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations,
      Retrofit retrofit) {
    if (getRawType(type) != Optional.class) {
      return null;
    }

    Type innerType = getParameterUpperBound(0, (ParameterizedType) type);
    Converter<ResponseBody, Object> delegate =
        retrofit.nextResponseBodyConverter(this, innerType, annotations);
    return new OptionalConverter<>(delegate);
  }
}