OkHttp 3 implementation of Volley's HttpStack

OkHttpStack.java

/*
 * Copyright (C) 2016 Eric Cochran
 *
 * 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.
 */

import com.android.volley.AuthFailureError;
import com.android.volley.Request;
import com.android.volley.toolbox.HttpStack;
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import okhttp3.Call;
import okhttp3.Headers;
import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.Protocol;
import okhttp3.RequestBody;
import okhttp3.Response;
import okhttp3.ResponseBody;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.ProtocolVersion;
import org.apache.http.StatusLine;
import org.apache.http.entity.BasicHttpEntity;
import org.apache.http.message.BasicHeader;
import org.apache.http.message.BasicHttpResponse;
import org.apache.http.message.BasicStatusLine;

/**
 * {@link HttpStack HttpStack} backed by OkHttp 3.
 */
public final class OkHttpStack implements HttpStack {
  private final OkHttpClient client;

  public OkHttpStack(OkHttpClient client) {
    this.client = client;
  }

  @Override
  public HttpResponse performRequest(Request<?> request, Map<String, String> additionalHeaders)
      throws IOException, AuthFailureError {
    OkHttpClient.Builder clientBuilder = client.newBuilder();
    int timeoutMs = request.getTimeoutMs();
    clientBuilder.connectTimeout(timeoutMs, TimeUnit.MILLISECONDS);
    clientBuilder.readTimeout(timeoutMs, TimeUnit.MILLISECONDS);
    clientBuilder.writeTimeout(timeoutMs, TimeUnit.MILLISECONDS);
    OkHttpClient client = clientBuilder.build();

    okhttp3.Request.Builder requestBuilder = new okhttp3.Request.Builder();
    requestBuilder.url(request.getUrl());

    setHeaders(requestBuilder, request, additionalHeaders);
    setConnectionParameters(requestBuilder, request);

    okhttp3.Request okHttpRequest = requestBuilder.build();
    Call okHttpCall = client.newCall(okHttpRequest);
    Response okHttpResponse = okHttpCall.execute();

    StatusLine responseStatus =
        new BasicStatusLine(parseProtocol(okHttpResponse.protocol()), okHttpResponse.code(),
            okHttpResponse.message());
    BasicHttpResponse response = new BasicHttpResponse(responseStatus);
    response.setEntity(getEntity(okHttpResponse));

    Headers responseHeaders = okHttpResponse.headers();
    for (int i = 0, len = responseHeaders.size(); i < len; i++) {
      response.addHeader(new BasicHeader(responseHeaders.name(i), responseHeaders.value(i)));
    }

    return response;
  }

  private static ProtocolVersion parseProtocol(Protocol p) {
    switch (p) {
      case HTTP_1_0:
        return new ProtocolVersion("HTTP", 1, 0);
      case HTTP_1_1:
        return new ProtocolVersion("HTTP", 1, 1);
      case SPDY_3:
        return new ProtocolVersion("SPDY", 3, 1);
      case HTTP_2:
        return new ProtocolVersion("HTTP", 2, 0);
    }
    throw new IllegalAccessError("Unknown protocol: " + p);
  }

  private static HttpEntity getEntity(Response response) throws IOException {
    BasicHttpEntity entity = new BasicHttpEntity();
    ResponseBody body = response.body();
    entity.setContent(body.byteStream());
    entity.setContentLength(body.contentLength());
    entity.setContentEncoding(response.header("Content-Encoding"));
    if (body.contentType() != null) {
      entity.setContentType(body.contentType().type());
    }
    return entity;
  }

  private static void setHeaders(okhttp3.Request.Builder builder, Request<?> request,
      Map<String, String> additionalHeaders) throws AuthFailureError {
    for (Map.Entry<String, String> entry : request.getHeaders().entrySet()) {
      builder.addHeader(entry.getKey(), entry.getValue());
    }
    for (Map.Entry<String, String> entry : additionalHeaders.entrySet()) {
      builder.addHeader(entry.getKey(), entry.getValue());
    }
  }

  private static void setConnectionParameters(okhttp3.Request.Builder builder, Request<?> request)
      throws AuthFailureError {
    switch (request.getMethod()) {
      case Request.Method.DEPRECATED_GET_OR_POST:
        // Ensure backwards compatibility. Volley assumes a request with a null body is a GET.
        byte[] postBody = request.getPostBody();
        if (postBody == null) {
          builder.get();
        } else {
          builder.post(
              RequestBody.create(MediaType.parse(request.getPostBodyContentType()), postBody));
        }
        break;
      case Request.Method.GET:
        builder.get();
        break;
      case Request.Method.DELETE:
        builder.delete();
        break;
      case Request.Method.POST:
        builder.post(createRequestBody(request));
        break;
      case Request.Method.PUT:
        builder.put(createRequestBody(request));
        break;
      case Request.Method.HEAD:
        builder.head();
        break;
      case Request.Method.OPTIONS:
        builder.method("OPTIONS", null);
        break;
      case Request.Method.TRACE:
        builder.method("TRACE", null);
        break;
      case Request.Method.PATCH:
        builder.patch(createRequestBody(request));
        break;
      default:
        throw new IllegalStateException("Unknown method type.");
    }
  }

  private static RequestBody createRequestBody(Request r) throws AuthFailureError {
    byte[] body = r.getBody();
    if (body == null) {
      return null;
    }
    return RequestBody.create(MediaType.parse(r.getBodyContentType()), body);
  }
}