The current implementation (in Beta4) accepts only GET and POST methods. If another method is passed in then the HttpMethod object will not be initialized and a NPE will be thrown.
additional HTTP methods has been added PUT DELETE which with already supported (GET and POST) covers most usage scenarios based on CRUD. Commit https://github.com/droolsjbpm/jbpm/commit/5f27171d58f198f95690bcc24e5e16817ab18879
Verified on ER3.