Now that the EZ install/boostrapping work is complete in the trunk and I've brought the roller_guice branch in line with the new regime, I'm ready to start talking DI again. This is the last bit of work that I'd like to get in before the 4.0 release.
Here's the start of the proposal: This proposal introduces DI in Roller in a pretty limited way. The idea is to get a DI framework into Roller so we can start rooting out our various factories and singletons, making the code easier to test, manage and providing more extension points. As it stands today it's only benefits are that it 1) allows a customizer to easily switch out Roller manager classes and replace them with their own implementations and 2) make it possible for RollerFactory to instantiate other Roller-dependent classes created by folks who are customizing 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 Roller API ** Do not change the was Roller back-end interfaces are accessed by front-end code ** i.e. RollerFactory.getRoller() stays in place * 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 implementations by setting a single property in the Roller configuration file. Read the rest here, with http://cwiki.apache.org/confluence/display/ROLLER/Proposal+Introduce+DI+with+Guice Comments? - Dave
