摘要：移除頭部參數然后再將自定義的攔截器設置為網絡攔截器信任所有證書設置應用攔截器無效，因為是在應用攔截器之后添加的這樣就能達到移除自動添加的請求頭參數的目的了。

使用OkHttp網絡框架在進行網絡請求時會發現，傳到后臺的請求頭中會比我們自己添加的參數多出幾個額外參數。查看源碼會發現

 private Response getResponseWithInterceptorChain() throws IOException {
    // Build a full stack of interceptors.
    List interceptors = new ArrayList<>();
    interceptors.addAll(client.interceptors());
    interceptors.add(retryAndFollowUpInterceptor);
    interceptors.add(new BridgeInterceptor(client.cookieJar()));
    interceptors.add(new CacheInterceptor(client.internalCache()));
    interceptors.add(new ConnectInterceptor(client));
    if (!retryAndFollowUpInterceptor.isForWebSocket()) {
      interceptors.addAll(client.networkInterceptors());
    }
    interceptors.add(new CallServerInterceptor(
        retryAndFollowUpInterceptor.isForWebSocket()));

    Interceptor.Chain chain = new RealInterceptorChain(
        interceptors, null, null, null, 0, originalRequest);
    return chain.proceed(originalRequest);
  }

OkHttp會默認添加一個橋接攔截器BridgeInterceptor，查看BridgeInterceptor的源碼

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"re responsible for also decompressing
    // the transfer stream.
    boolean transparentGzip = false;
    if (userRequest.header("Accept-Encoding") == null) {
      transparentGzip = true;
      requestBuilder.header("Accept-Encoding", "gzip");
    }

    List 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());
    }

在BridgeInterceptor中會默認添加User-Agent，Accept-Encoding等請求頭參數。有時候我們并不需要這些默認添加的參數，那么我們如何才能做到移除它們呢？

通過上面第一段的部分源碼

interceptors.add(retryAndFollowUpInterceptor);
interceptors.add(new BridgeInterceptor(client.cookieJar()));
interceptors.add(new CacheInterceptor(client.internalCache()));
interceptors.add(new ConnectInterceptor(client));
if (!retryAndFollowUpInterceptor.isForWebSocket()) {
  interceptors.addAll(client.networkInterceptors());
}

可以看到OkHttp內部在添加完BridgeInterceptor后，才開始添加networkInterceptors，所以我們需要借助網絡攔截器來重新攔截請求頭，并操作頭部參數。

首先我們要自定義一個攔截器，在攔截器中移除我們不需要的參數。

public class NetInterceptorimplements Interceptor {

    private HttpClient builder;

    public NetInterceptor() {
        super();
    }

    public NetInterceptor(HttpClient builder) {
        this.builder = builder;
    }

    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        //移除頭部參數
        request = request.newBuilder()
                    .removeHeader("User-Agent")
                    .removeHeader("Accept-Encoding")
                    .build();
        Response response = chain.proceed(request);
        if (response.body() != null && response.body().contentType() != null) {
            MediaType mediaType = response.body().contentType();
            String content = response.body().string();
            ResponseBody responseBody = ResponseBody.create(mediaType, content);
            return response.newBuilder().body(responseBody).build();
        } else {
            return response;
        }
    }

}

然后再將自定義的攔截器設置為網絡攔截器

  mOkBuilder = new Builder()
                .connectTimeout(mbuilder.getConnectTimeout(), TimeUnit.SECONDS)
                .readTimeout(mbuilder.getReadTimeout(), TimeUnit.SECONDS)
                .writeTimeout(mbuilder.getWriteTimeout(), TimeUnit.SECONDS)
                .sslSocketFactory(createSSLSocketFactory(), new TrustAllCerts())// 信任所有證書
                .hostnameVerifier(new TrustAllHostnameVerifier())
                .cookieJar(new CookieJar() {
                    private final HashMap> cookieStore = new HashMap<>();

                    @Override
                    public void saveFromResponse(HttpUrl httpUrl, List list) {
                        cookieStore.put(httpUrl.host(), list);
                    }

                    @Override
                    public List loadForRequest(HttpUrl httpUrl) {
                        List cookies = cookieStore.get(httpUrl.host());
                        return cookies != null ? cookies : new ArrayList();
                    }
                });

  NetInterceptor netInterceptor = new NetInterceptor(mbuilder);
  //mOkBuilder.addNetworkInterceptor(netInterceptor);//設置應用攔截器無效，因為BridgeInterceptor是在應用攔截器之后添加的
  mOkBuilder.addNetworkInterceptor(netInterceptor);

這樣就能達到移除BridgeInterceptor自動添加的請求頭參數的目的了。