Proposal Introduce DI with Guice

Status	Proposal not ready for review
Target Release	4.0
Original Authors	Dave Johnson

Abstract

This is a proposal to use Guice to implement Dependency Injection (DI) in Roller.

These requirements are met by this proposal.

Introduce DI Use DI to setup the Roller instance and managers, i.e. manager classes should no longer be hard-coded into the Roller implementation class, instead they should be injected.
- Enforce singletons, i.e. singletons should have a private constructor.
- Use constructor injection to ensure that immutable objects remain immutable.
Do not change way Roller is configured
- Do not introduce any additional configuration files for those installing Roller, i.e. don't change the fact that the only customization file users should ever have to touch is roller-custom.properties.
- Do not introduce any additional configuration files for developers, i.e. developers should not have to deal with any new XML or property files.
- Maintain the same level of back-end pluggability, i.e. it should still be possible to switch back-end implemenations by setting a single property in the Roller config.

List and describe new manager methods, Struts actions, JSP pages, macros, etc.

Other can leave commments here.