Currently the ApacheHttpClient class references org.apache.commons.httpclient.MultiThreadedHttpConnectionManager which exists in HttpClient 3.1. However, as noted on the Apache HttpComponents page,
Commons HttpClient 3.x codeline is at the end of life. All users of Commons HttpClient 3.x are strongly encouraged to upgrade to HttpClient 4.1.
MultiThreadedHttpConnectionManager does not exist in 4.1.
We have moved our HttpComponent dependecies from 3.x to 4.1 but Jersey is holding us back from completing the transition.