[xwiki-devs] [PROPOSAL] Implement decorators in xwiki-platform-container

Hi devs, This proposal is related to the following discussion on IRC : https://botbot.me/freenode/xwiki/2018-01-08/?msg=95495049&page=5 Abstract: We currently have an abstraction of the notion of a "container" defined in xwiki-platform-container-api [1]. This abstraction is very basic, but allows XWiki to support two different types of containers : Servlet and Portlet, and maybe support other types in the future. Problem: As those abstractions are very basic, it's quite hard to use them without downcasting them. A common example is the following: if I want to send a redirection in a Response object [2], I will need either to forge my own output that returns the correct HTTP code, with the correct header, etc … or I can downcast the given Response to all of its possible implementations and, for each implementation, find the correct method to use for sending a redirect. In order to avoid such tricks in the future, we could implement decorators that will allow Request and Response implementations to handle certain actions. In my previous example, a Response implementing RedirectResponse would expose a method `#sendRedirect(String url)`. The advantage here is that we don't really need to know on which Response implementation we are working on. WDYT ? Thanks, Clément [1] https://github.com/xwiki/xwiki-platform/tree/master/xwiki-platform-core/xwi… [2] https://github.com/xwiki/xwiki-platform/blob/master/xwiki-platform-core/xwi…