(3)—- BridgeInterceptor

series

OKio source code analysis

OKHttp source code parsing (1)—- overall process

OKHttp source code parsing (2) – RetryAndFollowUpInterceptor interceptor

(3)—- BridgeInterceptor

(4)—- CacheInterceptor

—- ConnectInterceptor

—- CallServerInterceptor

1. Introduction

Bridges from application code to network code. First it builds a network request from a user request. Then it proceeds to call the network. Finally it builds a user response from the network response.

Bridging interceptors (content interceptors) convert user-constructed requests into requests sent to the server and responses returned by the server into user-friendly responses.

2. Source code analysis

@Override Public Response Intercept (Chain Chain) throws IOException {// Constructs a user-friendly request as a request request sent to the server userRequest = chain.request(); Request.Builder requestBuilder = userRequest.newBuilder(); RequestBody body = userRequest.body(); // If there is a request body, constructif(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"); }}if (userRequest.header("Host") == null) {
      requestBuilder.header("Host", hostHeader(userRequest.url(), false));
    }

    if (userRequest.header("Connection") == null) {
      requestBuilder.header("Connection"."Keep-Alive");
    }

    // If we add an "Accept-Encoding: gzip" header field we are responsible for also decompressing
    // the transfer stream.
    boolean transparentGzip = false;
    if (userRequest.header("Accept-Encoding") == null && userRequest.header("Range") == null) {
      transparentGzip = true;
      requestBuilder.header("Accept-Encoding"."gzip"); } // Set cookie 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()); } // Once constructed, pass the request to the next interceptor for processing. NetworkResponse networkResponse = chain.proceed(requestBuilder.build()); / / save networkResponse cookie HttpHeaders. ReceiveHeaders (cookieJar userRequest. Url (), networkResponse headers ()); / / will networkResponse structure for user-friendly response response. The Builder responseBuilder. = networkResponse newBuilder () .request(userRequest); // If networkResponse uses gzip and has a response body, set the response body to a user-friendly responseif (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);
      responseBuilder.body(new RealResponseBody(strippedHeaders, Okio.buffer(responseBody)));
    }

    return responseBuilder.build();
  }
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BridgeInterceptor does two things: request header and response handling:

• Request header processing: Get the user’s request requestBuilder and complete the request header information in the request. Examples are content-type, Content-Length, Transfer-encoding, Host, Connection, Accept-encoding, Cookie, and User-agent
• Response: After receiving the response, place the requested request in the response, and set the body of the response to a user-friendly response if the response is gZIP encoded and has a body

Additional:

HTTP headers:

The Http response headers

References

HTTP request headers and request bodies

HTTP headers – Common HTTP request and response headers