HostConfiguration doesn't use its host.protocol to execute an HttpMethod with an absolute URL. It should, if the Protocol's scheme is the same as the method's URL scheme.
This bug makes it difficult to integrate a specialized SSL connection algorithm (in a SecureProtocolSocketFactory) with a module implemented on top of HttpClient. The latter module must not execute methods with absolute URLs. Of course, this is difficult when one doesn't control that module. For example, I recently tried to integrate SSL certificate-based client authentication with XFire. XFire provides a reasonable API for replacing its HttpClient, but one must hack its source code to prevent it from executing methods with absolute URLs.
Protocol.registerProtocol is a possible answer, but it can't support two or more SSL connection algorithms for one HTTPS host and port.