Allow custom authentication mechanism for the Java client

[rhuss]

Currently the Java client allows only Basic Authentication. However, the karaf deployed hawt.io uses a different mechanism:

• A POST with the Basic-Auth included preemptively needs to be sent to /hawtio/auth/login
• The response then sets the corresponding session-cookie

In order to allow such a custom authentication mechanism, hooks must be added perform this login step in advance.

See also the discussion at the Jolokia Forum

[rhuss]

A base implementation has been already implemented (though not yet pushed). In the meantime one can prepare an HttpClient (i.e. performing the steps above) and the using the public constructor of J4pClient with this client (which then already should have the session cookie).

[rhuss]

It turns out, that for hawt.io it is sufficient to simply use preemptive Basic-Authentication.

So the following should do the trick for now

J4pClient j4p = J4pClient.url("..").user("karaf").password("karaf").build();
DefaultHttpClient client = (DefaultHttpClient) j4p.getHttpClient();
client.addRequestInterceptor(new PreemptiveAuthInterceptor());

with the PreemptiveAuthInterceptor taken from Stackoverflow