retrofit源码解析--异步请求

Retrofit.png

retrofit请求具体实现类为OkHttpCall，所以本篇直接来到OkHttpCall分析它的异步请求

final class OkHttpCall<T> implements Call<T> {
  private final ServiceMethod<T, ?> serviceMethod;
  private final @Nullable Object[] args;

  private volatile boolean canceled;

  @GuardedBy("this")
1 private @Nullable okhttp3.Call rawCall;
  @GuardedBy("this")
  private @Nullable Throwable creationFailure; // Either a RuntimeException or IOException.
  @GuardedBy("this")
  private boolean executed;

  @Override public void enqueue(final Callback<T> callback) {
    checkNotNull(callback, "callback == null");

    okhttp3.Call call;
    Throwable failure;

    synchronized (this) {
      if (executed) throw new IllegalStateException("Already executed.");
      executed = true;
2     call = rawCall = createRawCall();
    }

    if (failure != null) {
      callback.onFailure(this, failure);
      return;
    }

    if (canceled) {
      call.cancel();
    }

3   call.enqueue(new okhttp3.Callback() {
      @Override public void onResponse(okhttp3.Call call, okhttp3.Response rawResponse)
          throws IOException {
        Response<T> response;
        try {
4         response = parseResponse(rawResponse);
        } catch (Throwable e) {
          callFailure(e);
          return;
        }
        callSuccess(response);
      }
    '省略部分代码'
  }

• 1.中看出retrofit实际网络请求使用的是原生的okhttp
• 2.createRawCall:

private okhttp3.Call createRawCall() throws IOException {
    Request request = serviceMethod.toRequest(args);
    okhttp3.Call call = serviceMethod.callFactory.newCall(request);
    if (call == null) {
      throw new NullPointerException("Call.Factory returned null.");
    }
    return call;
}

从serviceMethod获取到请求参数并封装成request对象返回，ServiceMethod主要就是将retrofit网络请求的各种参数进行封装，是retrofit的核心部件。
将获取到的request传入okhttp的RealCall获取到原生RealCall对象

• 3.调用RealCall的异步方法enqueue
• 4.将获取到的返回进行解析parseResponse，在返回到retrofit的callback:

Response<T> parseResponse(okhttp3.Response rawResponse) throws IOException {
  ResponseBody rawBody = rawResponse.body();

  // Remove the body's source (the only stateful object) so we can pass the response along.
  rawResponse = rawResponse.newBuilder()
      .body(new NoContentResponseBody(rawBody.contentType(), rawBody.contentLength()))
      .build();

  int code = rawResponse.code();
  if (code < 200 || code >= 300) {
    try {
      // Buffer the entire body to avoid future I/O.
      ResponseBody bufferedBody = Utils.buffer(rawBody);
      return Response.error(bufferedBody, rawResponse);
    } finally {
      rawBody.close();
    }
  }

  if (code == 204 || code == 205) {
    rawBody.close();
    return Response.success(null, rawResponse);
  }

  ExceptionCatchingRequestBody catchingBody = new ExceptionCatchingRequestBody(rawBody);
  try {
    T body = serviceMethod.toResponse(catchingBody);
    return Response.success(body, rawResponse);
  } catch (RuntimeException e) {
    // If the underlying source threw an exception, propagate that rather than indicating it was
    // a runtime exception.
    catchingBody.throwIfCaught();
    throw e;
  }
}