探究OkHttpClient的运行原理（3---BridgeIn

本篇文章继续深入源代码查看 BridgeInterceptor 拦截器相关的方法

BridgeInterceptor

查看 intercept 方法

  @Override public Response intercept(Chain chain) throws IOException {
    Request userRequest = chain.request();// 取出 Request 实例
    Request.Builder requestBuilder = userRequest.newBuilder();创建 Builder

    RequestBody body = userRequest.body();// 取出body对象
    if (body != null) {
      MediaType contentType = body.contentType();
      if (contentType != null) { //赋值 contentType 给 builder
        requestBuilder.header("Content-Type", contentType.toString());
      }

      long contentLength = body.contentLength();
      if (contentLength != -1) { // 赋值contentLength
        requestBuilder.header("Content-Length", Long.toString(contentLength));
        requestBuilder.removeHeader("Transfer-Encoding");
      } else {
        requestBuilder.header("Transfer-Encoding", "chunked");
        requestBuilder.removeHeader("Content-Length");
      }
    }

    if (userRequest.header("Host") == null) {  // 赋值Host
      requestBuilder.header("Host", hostHeader(userRequest.url(), false));
    }

    if (userRequest.header("Connection") == null) { // 赋值Connection
      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) { // 赋值 Accept-Encoding
      transparentGzip = true;
      requestBuilder.header("Accept-Encoding", "gzip");
    }

    List<Cookie> cookies = cookieJar.loadForRequest(userRequest.url());
    if (!cookies.isEmpty()) {// 赋值 cookie
      requestBuilder.header("Cookie", cookieHeader(cookies));
    }

    if (userRequest.header("User-Agent") == null) {// 赋值 User-Agent
      requestBuilder.header("User-Agent", Version.userAgent());
    }

    Response networkResponse = chain.proceed(requestBuilder.build());// 调用下一个拦截器

    HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());

    Response.Builder responseBuilder = networkResponse.newBuilder()
        .request(userRequest);

    if (transparentGzip
        && "gzip".equalsIgnoreCase(networkResponse.header("Content-Encoding"))
        && HttpHeaders.hasBody(networkResponse)) { // 解析返回数据
      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();
  }

可以看到 BridgeInterceptor 拦截器主要是取 Request 中的参数最后赋值给其内部类 requestBuilder ，requestBuilder 在之前构造 Request 已经对其进行实例化，此处即进行相关赋值；

总结 BridgeInterceptor 做了什么？
1、根据请求我们设置的参数，赋值 Request 相关数据到 Builder 中；
2、解析返回的数据；