okhttp 3：如何使用Java / Android手动解压缩gzip / deflate响应

Question

我知道okhttp3默认情况下，该库会添加标头Accept-Encoding: gzip并自动为我们解码响应。

我要处理的主机仅接受标头的问题是：Accept-Encoding: gzip, deflate如果不添加deflate部分，它将失败。现在，当我手动将该标头添加到okhttp客户端时，该库不再对我进行解压缩。

我已经尝试了多种解决方案来获取响应并尝试手动解压缩该响应，但是我总是最终遇到一个异常，即java.util.zip.ZipException: Not in GZIP format，这是我到目前为止已经尝试的方法：

//decompresser
public static String decompressGZIP(InputStream inputStream) throws IOException
{
    InputStream bodyStream = new GZIPInputStream(inputStream);
    ByteArrayOutputStream outStream = new ByteArrayOutputStream();
    byte[] buffer = new byte[4096];
    int length;
    while ((length = bodyStream.read(buffer)) > 0) 
    {
        outStream.write(buffer, 0, length);
    }

    return new String(outStream.toByteArray());
}


//run scraper
scrape(api, new Callback()
{
    // Something went wrong
    @Override
    public void onFailure(@NonNull Call call, @NonNull IOException e)
    {
    }

    @Override
    public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException
    {
        if (response.isSuccessful())
        {
            try
            {
                InputStream responseBodyBytes = responseBody.byteStream();
                returnedObject = GZIPCompression.decompress(responseBodyBytes);

                if (returnedObject != null)
                {
                    String htmlResponse = returnedObject.toString();
                }
            }
            catch (ProtocolException e){}

            if(response != null) response.close();
        }
    }
});



private Call scrape(Map<?, ?> api, Callback callback)
{
    MediaType JSON = MediaType.parse("application/json; charset=utf-8");
    String method = (String) api.get("method");
    String url = (String) api.get("url");
    Request.Builder requestBuilder = new Request.Builder().url(url);
    RequestBody requestBody;

    requestBuilder.header("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:61.0) Gecko/20100101 Firefox/61.0");
    requestBuilder.header("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");
    requestBuilder.header("Accept-Language", "en-US,en;q=0.5");
    requestBuilder.header("Accept-Encoding", "gzip, deflate");
    requestBuilder.header("Connection", "keep-alive");
    requestBuilder.header("Upgrade-Insecure-Requests", "1");
    requestBuilder.header("Cache-Control", "max-age=0");

    Request request = requestBuilder.build();

    Call call = client.newCall(request);
    call.enqueue(callback);

    return call;
}

请注意，响应标头将始终返回Content-Encoding: gzip并Transfer-Encoding: chunked

还有一件事，我也尝试了本主题中的解决方案，但仍然失败D/OkHttp: java.io.IOException: ID1ID2: actual 0x00003c68 != expected 0x00001f8b。

任何帮助，将不胜感激..

Answer 1

经过6个小时的挖掘，我找到了正确的解决方案，并且像往常一样，它比我想象的要容易，所以我基本上是在尝试解压缩未解压缩的页面，原因是该页面失败了。现在，一旦我进入第二页（压缩的页面），我就会得到一个压缩的响应，上面的代码应该在该响应上进行处理。另外，如果有人想要该解决方案，我就像在此答案中一样使用了一个经过修改的拦截器，因此您无需使用自定义函数来处理解压缩。

我修改了unzip方法，使okhttp interceptor可以处理压缩和未压缩的响应：

    OkHttpClient.Builder clientBuilder = new OkHttpClient.Builder().addInterceptor(new UnzippingInterceptor());
    OkHttpClient client = clientBuilder.build();

拦截器就像dis：

private class UnzippingInterceptor implements Interceptor {
    @Override
    public Response intercept(Chain chain) throws IOException {
        Response response = chain.proceed(chain.request());
        return unzip(response);


    // copied from okhttp3.internal.http.HttpEngine (because is private)
    private Response unzip(final Response response) throws IOException
    {
        if (response.body() == null)
        {
            return response;
        }

        //check if we have gzip response
        String contentEncoding = response.headers().get("Content-Encoding");

        //this is used to decompress gzipped responses
        if (contentEncoding != null && contentEncoding.equals("gzip"))
        {
            Long contentLength = response.body().contentLength();
            GzipSource responseBody = new GzipSource(response.body().source());
            Headers strippedHeaders = response.headers().newBuilder().build();
            return response.newBuilder().headers(strippedHeaders)
                    .body(new RealResponseBody(response.body().contentType().toString(), contentLength, Okio.buffer(responseBody)))
                    .build();
        }
        else
        {
            return response;
        }
    }
}
}