As per the below code
jbosh/BOSHClient.java at master · igniterealtime/jbosh · GitHub
The line 235 ..... private final HTTPSender httpSender = ServiceLib.loadService(HTTPSender.class); .... which is indirectly refers a ".properties" file
My Suggestion is
Similar to our smack packet extension providers, this should be a developer/user customisable ..... so that either Apache HttpClient 4.x or UrlConnection or any other can be chosen appropriately