public class RequestInterceptor implements Interceptor {
    public RequestInterceptor() {
    }
    @Override
    public Response intercept(Chain chain) throws IOException {
        Request.Builder builder = chain.request()
                .newBuilder()
                .addHeader("Accept", "application/json")
                .addHeader("Accept-Encoding", "gzip");
        Request request = builder.build();         
        return chain.proceed(request);
    }
}

public final class BridgeInterceptor implements Interceptor {
  private final CookieJar cookieJar;
  public BridgeInterceptor(CookieJar cookieJar) {
    this.cookieJar = cookieJar;
  }
  @Override public Response intercept(Chain chain) throws IOException {
    Request userRequest = chain.request();
    Request.Builder requestBuilder = userRequest.newBuilder();
    RequestBody body = userRequest.body();
    if (body != null) {
      MediaType contentType = body.contentType();
      //自動增添加請求頭 Content-Type
      if (contentType != null) {
        requestBuilder.header("Content-Type", contentType.toString());
      }
      long contentLength = body.contentLength();
      //如果傳輸長度不為-1，則表示完整傳輸
      if (contentLength != -1) {
        //設置頭信息 Content-Length
        requestBuilder.header("Content-Length", Long.toString(contentLength));
        requestBuilder.removeHeader("Transfer-Encoding");
      } else {
        //如果傳輸長度為-1，則表示分塊傳輸，自動設置頭信息         
        requestBuilder.header("Transfer-Encoding", "chunked");
        requestBuilder.removeHeader("Content-Length");
      }
    }
    if (userRequest.header("Host") == null) {
      requestBuilder.header("Host", hostHeader(userRequest.url(), false));
    }
    //如果沒有設置頭信息 Connection，則自動設置為 Keep-Alive
    if (userRequest.header("Connection") == null) {
      requestBuilder.header("Connection", "Keep-Alive");
    }
    // If we add an "Accept-Encoding: gzip" header field we're responsible for also decompressing
    // the transfer stream.
    boolean transparentGzip = false;
    if (userRequest.header("Accept-Encoding") == null && userRequest.header("Range") == null) {
      //如果我們沒有在請求頭信息里增加Accept-Encoding，在這里會自動設置頭信息 Accept-Encoding = gzip
      transparentGzip = true;
      requestBuilder.header("Accept-Encoding", "gzip");
    }
    List<Cookie> cookies = cookieJar.loadForRequest(userRequest.url());
    if (!cookies.isEmpty()) {
      requestBuilder.header("Cookie", cookieHeader(cookies));
    }
    if (userRequest.header("User-Agent") == null) {
      requestBuilder.header("User-Agent", Version.userAgent());
    }
    Response networkResponse = chain.proceed(requestBuilder.build());
    HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());
    Response.Builder responseBuilder = networkResponse.newBuilder()
        .request(userRequest);
    //如果返回的頭信息里Content-Encoding = gzip，并且我們沒有手動在請求頭信息里設置 Accept-Encoding = gzip，則會進行 gzip 解壓數據流
    if (transparentGzip
        && "gzip".equalsIgnoreCase(networkResponse.header("Content-Encoding"))
        && HttpHeaders.hasBody(networkResponse)) {
      GzipSource responseBody = new GzipSource(networkResponse.body().source());
      Headers strippedHeaders = networkResponse.headers().newBuilder()
          .removeAll("Content-Encoding")
          .removeAll("Content-Length")
          .build();
      responseBuilder.headers(strippedHeaders);
      String contentType = networkResponse.header("Content-Type");
      responseBuilder.body(new RealResponseBody(contentType, -1L, Okio.buffer(responseBody)));
    }
    return responseBuilder.build();
  }
}