JsonQueryParameters.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 okhttp3.mockwebserver.RecordedRequest;
import okio.Buffer;
import retrofit2.Call;
import retrofit2.Converter;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;
import retrofit2.http.GET;
import retrofit2.http.Query;

import static java.lang.annotation.RetentionPolicy.RUNTIME;

public final class JsonQueryParameters {
  @Retention(RUNTIME)
  @interface Json {
  }

  static class JsonStringConverterFactory extends Converter.Factory {
    private final Converter.Factory delegateFactory;

    JsonStringConverterFactory(Converter.Factory delegateFactory) {
      this.delegateFactory = delegateFactory;
    }

    @Override public Converter<?, String> stringConverter(Type type, Annotation[] annotations,
        Retrofit retrofit) {
      for (Annotation annotation : annotations) {
        if (annotation instanceof Json) {
          // NOTE: If you also have a JSON converter factory installed in addition to this factory,
          // you can call retrofit.requestBodyConverter(type, annotations) instead of having a
          // reference to it explicitly as a field.
          Converter<?, RequestBody> delegate =
              delegateFactory.requestBodyConverter(type, annotations, new Annotation[0], retrofit);
          return new DelegateToStringConverter<>(delegate);
        }
      }
      return null;
    }

    static class DelegateToStringConverter<T> implements Converter<T, String> {
      private final Converter<T, RequestBody> delegate;

      DelegateToStringConverter(Converter<T, RequestBody> delegate) {
        this.delegate = delegate;
      }

      @Override public String convert(T value) throws IOException {
        Buffer buffer = new Buffer();
        delegate.convert(value).writeTo(buffer);
        return buffer.readUtf8();
      }
    }
  }

  static class Filter {
    final String userId;

    Filter(String userId) {
      this.userId = userId;
    }
  }

  interface Service {
    @GET("/filter")
    Call<ResponseBody> example(@Json @Query("value") Filter value);
  }

  public static void main(String... args) throws IOException, InterruptedException {
    MockWebServer server = new MockWebServer();
    server.start();
    server.enqueue(new MockResponse());

    Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(server.url("/"))
        .addConverterFactory(new JsonStringConverterFactory(GsonConverterFactory.create()))
        .build();
    Service service = retrofit.create(Service.class);

    Call<ResponseBody> call = service.example(new Filter("123"));
    Response<ResponseBody> response = call.execute();
    // TODO handle user response...

    // Print the request path that the server saw to show the JSON query param:
    RecordedRequest recordedRequest = server.takeRequest();
    System.out.println(recordedRequest.getPath());

    server.shutdown();
  }
}