OkHttp 在最终构建请求信息以及处理返回信息时，内部使用了一个叫做 BridgeInterceptor 的拦截器，该类的代码如下：

public final class BridgeInterceptor implements Interceptor {
    private final CookieJar cookieJar;

    public BridgeInterceptor(CookieJar cookieJar) {
        this.cookieJar = cookieJar;
    }

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

        RequestBody body = userRequest.body();
        if (body != null) {
            MediaType contentType = body.contentType();
            //自动增添加请求头 Content-Type
            if (contentType != null) {
                requestBuilder.header("Content-Type", contentType.toString());
            }

            long contentLength = body.contentLength();
            //如果传输长度不为-1，则表示完整传输
            if (contentLength != -1) {
                //设置头信息 Content-Length
                requestBuilder.header("Content-Length", Long.toString(contentLength));
                requestBuilder.removeHeader("Transfer-Encoding");
            } else {
                //如果传输长度为-1，则表示分块传输，自动设置头信息         
                requestBuilder.header("Transfer-Encoding", "chunked");
                requestBuilder.removeHeader("Content-Length");
            }
        }

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

        //如果没有设置头信息 Connection，则自动设置为 Keep-Alive
        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 && userRequest.header("Range") == null) {
            //如果我们没有在请求头信息里增加Accept-Encoding，在这里会自动设置头信息 Accept-Encoding = gzip
            transparentGzip = true;
            requestBuilder.header("Accept-Encoding", "gzip");
        }

        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());
        }

        Response networkResponse = chain.proceed(requestBuilder.build());

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

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

        //如果返回的头信息里Content-Encoding = gzip，并且我们没有手动在请求头信息里设置 Accept-Encoding = gzip，则会进行 gzip 解压数据流
        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();
    }
}

混淆后

public final class a implements v {

    /* renamed from: a  reason: collision with root package name */
    private final m f33903a;

    public a(m mVar) {
        this.f33903a = mVar;
    }

    @Override // okhttp3.v
    public b0 a(v.a aVar) throws IOException {
        z J = aVar.J();
        z.a f2 = J.f();
        a0 a2 = J.a();
        if (a2 != null) {
            w c2 = a2.c();
            if (c2 != null) {
                f2.b("Content-Type", c2.toString());
            }
            long b2 = a2.b();
            if (b2 != -1) {
                f2.b("Content-Length", Long.toString(b2));
                f2.a("Transfer-Encoding");
            } else {
                f2.b("Transfer-Encoding", "chunked");
                f2.a("Content-Length");
            }
        }
        boolean z = false;
        if (J.a("Host") == null) {
            f2.b("Host", b.a(J.h(), false));
        }
        if (J.a("Connection") == null) {
            f2.b("Connection", c.w);
        }
        if (J.a("Accept-Encoding") == null && J.a("Range") == null) {
            z = true;
            f2.b("Accept-Encoding", "gzip");
        }
        List<l> a3 = this.f33903a.a(J.h());
        if (!a3.isEmpty()) {
            f2.b("Cookie", a(a3));
        }
        if (J.a("User-Agent") == null) {
            f2.b("User-Agent", okhttp3.internal.c.a());
        }
        b0 a4 = aVar.a(f2.a());
        e.a(this.f33903a, J.h(), a4.v());
        b0.a a5 = a4.z().a(J);
        if (z && "gzip".equalsIgnoreCase(a4.c("Content-Encoding")) && e.b(a4)) {
            GzipSource gzipSource = new GzipSource(a4.c().t());
            a5.a(a4.v().c().d("Content-Encoding").d("Content-Length").a());
            a5.a(new h(a4.c("Content-Type"), -1, Okio.buffer(gzipSource)));
        }
        return a5.a();
    }
}