okhttp 之BridgeInterceptor（设置一些通用的请求头等等） 拦截器分析

首先我们还是进入 intercept(Chain chain) 这个方法

      //首先都是一些协议字段的判断
  @Override public Response intercept(Chain chain) throws IOException {
  //首先拿到上一级的请求
    Request userRequest = chain.request();
   Request.Builder requestBuilder = userRequest.newBuilder();

RequestBody body = userRequest.body();

if (body != null) {
  MediaType contentType = body.contentType();
  if (contentType != null) {
    requestBuilder.header("Content-Type", contentType.toString());
  }

  long contentLength = body.contentLength();
  if (contentLength != -1) {
    requestBuilder.header("Content-Length", Long.toString(contentLength));
    requestBuilder.removeHeader("Transfer-Encoding");
  } else {
    requestBuilder.header("Transfer-Encoding", "chunked");
    requestBuilder.removeHeader("Content-Length");
  }
}
   //判断域名
if (userRequest.header("Host") == null) {
  requestBuilder.header("Host", hostHeader(userRequest.url(), false));
}
//重要的头信息  设置连接
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;
  //判断Accept-Encoding  默认设置压缩 gzip
if (userRequest.header("Accept-Encoding") == null && userRequest.header("Range") == null) {
  transparentGzip = true;
  requestBuilder.header("Accept-Encoding", "gzip");
}

List<Cookie> cookies = cookieJar.loadForRequest(userRequest.url());
   //判断cookies
if (!cookies.isEmpty()) {
  requestBuilder.header("Cookie", cookieHeader(cookies));
}
 //进行User-Agent 协议字段的判断
if (userRequest.header("User-Agent") == null) {
  requestBuilder.header("User-Agent", Version.userAgent());
}

Response networkResponse = chain.proceed(requestBuilder.build());
//处理保存cookie
HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());

Response.Builder responseBuilder = networkResponse.newBuilder()
    .request(userRequest);
 //进行判断 如果后台吧这些资源 进行gzip压缩了 则利用GzipSource okio的输入流
 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();

}