什么是Interceptor：

Interceptor翻譯過來就是攔截器竟趾，它是OkHttp網絡請求中抓取請求和響應必須的一個全能王漾峡。

你如果用過okhttp定欧，一定對HttpLoggingInterceptor不陌生信殊，這個是squareup公司寫的一個樣板挽绩，其實它呢也就是告訴你了任何你想拿到的數據⊙咚看源碼么赵刑，go。场刑。般此。

public final class HttpLoggingInterceptor implements Interceptor {
  private static final Charset UTF8 = Charset.forName("UTF-8");
//設置攔截級別，枚舉4種
  public enum Level {
    NONE,
    BASIC,
    HEADERS,
    BODY
  }
牵现。铐懊。。瞎疼。科乎。。贼急。茅茂。捏萍。。
空闲。令杈。。碴倾。逗噩。。影斑。。机打。矫户。
。残邀。皆辽。。芥挣。驱闷。。空免。空另。。
  @Override public Response intercept(Chain chain) throws IOException {
    Level level = this.level;
    Request request = chain.request();
    if (level == Level.NONE) {
      //不攔截蹋砚，直接返回
      return chain.proceed(request);
    }
    boolean logBody = level == Level.BODY;
    boolean logHeaders = logBody || level == Level.HEADERS;
    RequestBody requestBody = request.body();
    boolean hasRequestBody = requestBody != null;
    //建立連接
    Connection connection = chain.connection();
    //拿到連接協議扼菠，如果連接不存在就直接用http_1_1協議
    Protocol protocol = connection != null ? connection.protocol() : Protocol.HTTP_1_1;
    String requestStartMessage = "--> " + request.method() + ' ' + request.url() + ' ' + protocol;
    //如果設置的級別是base，就打印頭部分
    if (!logHeaders && hasRequestBody) {
      requestStartMessage += " (" + requestBody.contentLength() + "-byte body)";
    }
    logger.log(requestStartMessage);
    //如果設置的級別是頭坝咐，就打印頭部分
    if (logHeaders) {
      //如果有請求體循榆，就將請求體的長度和類型打印
      if (hasRequestBody) {
        //請求頭的值，存在就攔截
        if (requestBody.contentType() != null) {
          logger.log("Content-Type: " + requestBody.contentType());
        }
        //-1代表請求數據長度0
        if (requestBody.contentLength() != -1) {
          logger.log("Content-Length: " + requestBody.contentLength());
        }
      }
      //請求頭部分墨坚，遍歷打印
      Headers headers = request.headers();
      for (int i = 0, count = headers.size(); i < count; i++) {
        String name = headers.name(i);
        // 這里因為上面已經打印了秧饮，所以就過濾一下
        if (!"Content-Type".equalsIgnoreCase(name) && !"Content-Length".equalsIgnoreCase(name)) {
          logger.log(name + ": " + headers.value(i));
        }
      }
      //沒有請求體，或者等級沒有設置為打印請求體泽篮，結束打印
      if (!logBody || !hasRequestBody) {
        logger.log("--> END " + request.method())盗尸；
      } else if (bodyEncoded(request.headers())) {
        //有請求體或者log等級設置為body，打印請求頭中設置的編碼
        logger.log("--> END " + request.method() + " (encoded body omitted)");
      } else {
        //將請求體數據給寫進緩存流
        Buffer buffer = new Buffer();
        requestBody.writeTo(buffer);
        //設置編碼為utf-8
        Charset charset = UTF8;
        MediaType contentType = requestBody.contentType();
        if (contentType != null) {
          charset = contentType.charset(UTF8);
        }

        logger.log("");
      //判斷是否是人類可讀的字符帽撑，是就打印
        if (isPlaintext(buffer)) {
          logger.log(buffer.readString(charset));
          logger.log("--> END " + request.method()
              + " (" + requestBody.contentLength() + "-byte body)");
        } else {
          //人類不懂振劳，就用二進制讀出來
          logger.log("--> END " + request.method() + " (binary "
              + requestBody.contentLength() + "-byte body omitted)");
        }
      }
    }

    long startNs = System.nanoTime();
    Response response;
    try {
      //請求開始
      response = chain.proceed(request);
    } catch (Exception e) {
      //請求異常
      logger.log("<-- HTTP FAILED: " + e);
      throw e;
    }
    //請求花費時間
    long tookMs = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNs);
    //響應體了
    ResponseBody responseBody = response.body();
    long contentLength = responseBody.contentLength();
    String bodySize = contentLength != -1 ? contentLength + "-byte" : "unknown-length";
    //打印長度和響應碼，響應信息油狂，響應體對應請求體（這里要考慮重定向url）历恐，請求耗費時間寸癌，響應體長度
    logger.log("<-- " + response.code() + ' ' + response.message() + ' '
        + response.request().url() + " (" + tookMs + "ms" + (!logHeaders ? ", "
        + bodySize + " body" : "") + ')');
    //打印響應頭
    if (logHeaders) {
      Headers headers = response.headers();
      for (int i = 0, count = headers.size(); i < count; i++) {
        logger.log(headers.name(i) + ": " + headers.value(i));
      }
       //響應體不存在，等級不為body
      if (!logBody || !HttpHeaders.hasBody(response)) {
        logger.log("<-- END HTTP");
      } else if (bodyEncoded(response.headers())) {
        //響應體編碼不對稱
        logger.log("<-- END HTTP (encoded body omitted)");
      } else {
        //source弱贼，響應體來了
        BufferedSource source = responseBody.source();
        //設置最大緩存大小蒸苇，當然是緩存整個body嘍，全吃
        source.request(Long.MAX_VALUE); 
        Buffer buffer = source.buffer()吮旅；
        Charset charset = UTF8;
        //拿到media類型對應的字符集
        MediaType contentType = responseBody.contentType();
        if (contentType != null) {
          try {
            charset = contentType.charset(UTF8);
          } catch (UnsupportedCharsetException e) {
            logger.log("");
            logger.log("Couldn't decode the response body; charset is likely malformed.");
            logger.log("<-- END HTTP");

            return response;
          }
        }
        //如果不是人類能看懂的溪烤，就不打印string形式的嘍
        if (!isPlaintext(buffer)) {
          logger.log("");
          logger.log("<-- END HTTP (binary " + buffer.size() + "-byte body omitted)");
          return response;
        }
        //是人類懂的，就開始讀string嘍
        if (contentLength != 0) {
          logger.log("");
          logger.log(buffer.clone().readString(charset));
        }
        //最后打印body的長度
        logger.log("<-- END HTTP (" + buffer.size() + "-byte body)");
      }
    }

    return response;
  }

  /**
   *判斷緩存流的數據是否是人類能讀懂的庇勃，哈哈檬嘀，也就是abc123唄
   */
  static boolean isPlaintext(Buffer buffer) {
     //先判斷是不是123abc能看懂的
    try {
      Buffer prefix = new Buffer();
      long byteCount = buffer.size() < 64 ? buffer.size() : 64;
      buffer.copyTo(prefix, 0, byteCount);
      for (int i = 0; i < 16; i++) {
        if (prefix.exhausted()) {
          break;
        }
        //再判斷是不是iso8859-1之類的，當然不是能懂的啊
        int codePoint = prefix.readUtf8CodePoint();
        if (Character.isISOControl(codePoint) && !Character.isWhitespace(codePoint)) {
          return false;
        }
      }
      return true;
    } catch (EOFException e) {
      return false; // Truncated UTF-8 sequence.
    }
  }
  //返回頭中的編碼是否存在并且不是identity责嚷，一般都是gzip,deflate,compress之中一個
  private boolean bodyEncoded(Headers headers) {
    String contentEncoding = headers.get("Content-Encoding");
    return contentEncoding != null && !contentEncoding.equalsIgnoreCase("identity");
  }
}

好了終于擼了一遍源碼鸳兽，相信還有很多朋友沒有看懂，解釋這些源碼干嘛啊罕拂，另外推薦一篇文章揍异，大家踴躍去看吧(感謝ychongjie的攔截器細致分析)：
鏈接直通車

沒有太多時間更新和維護，有什么不妥的請指出爆班，匆忙的成果衷掷，畢竟公司團隊項目你不做其他人多做，多少有點坑隊友柿菩，dota骨灰級玩家怎么能做出這種事情呢戚嗅，不定期更新中。枢舶。渡处。