How do I get chunked footers from a response on a connection that uses ThreadSafeClientConnManager?

Question

I'm using a connection created by ThreadSafeClientConnManager (Apache httpcomponents 4.1.1). The response is chunked (which I expect), as is determined by response.getEntity().isChunked()

However, there is no way to get the footers/trailers (which are necessary for our application). Since the response was chunked, I would expect the entity contents to be of type ChunkedInputStream, however the default request director and executor classes used by the client wrap the original response entity (which, from looking at the httpcomponents source would have been a ChunkedInputStream) in a BasicManagedEntity.

In short, I am no longer able to get the footers/trailers off of the response, as BasicManagedEntity does not make the underlying entity available for use. Does anyone know how to work around this?

For reference, see:

org.apache.http.impl.client.DefaultRequestDirector.java, lines 523-525
org.apache.http.impl.entity.EntityDeserializer.java, lines 93-96

Side note: I've fixed this for now by implementing various subclasses and wrappers for HttpClient, HttpResponse, and HttpRequestExecutor, but I'm still looking for a better solution! — Brian, Jul 07 '11 at 22:31

score 4 · Accepted Answer · answered Jul 08 '11 at 11:40

One can use an HTTP response interceptor in order to access to the chunked content stream and response footers.

httpclient.addResponseInterceptor(new HttpResponseInterceptor() {

public void process(
        final HttpResponse response,
        final HttpContext context) throws HttpException, IOException {
    HttpEntity entity = response.getEntity();
    if (entity != null) {
        InputStream instream = entity.getContent();
        if (instream instanceof ChunkedInputStream) {
            Header[] footers = ((ChunkedInputStream) instream).getFooters();
        }
    }
}

});

score 0 · Answer 2 · answered Feb 09 '21 at 06:41

As described in the answer, this can be done when using the deprecated DefaultHttpClient. For the newer non-deprecated HttpClients, there is a bug https://issues.apache.org/jira/browse/HTTPCLIENT-1992 which prevents trailers from being accessed in version 4.5. This bug has been fixed in 5.0

So in v4.5, below won't work.

 CloseableHttpClient httpclient = HttpClients.custom().addInterceptorFirst(
            (org.apache.http.HttpResponse response, HttpContext context) -> {
                InputStream instream = response.getEntity().getContent();
                if (instream instanceof ChunkedInputStream) {
                    //Code will never run for v4.5
                }
            }
    ).build();

How do I get chunked footers from a response on a connection that uses ThreadSafeClientConnManager?

2 Answers2