Series
Part 1
At work I wire Play apps by hand with the cake pattern. In my own projects I switched a Play 3 template to Guice: one deleted config line, one @Inject(), and a timestamp that made me think Guice was broken.
Part 2
A test that could not pass forced my first trait into the graph. @ImplementedBy, a root Module, a test that builds the real Guice graph, and the error Guice prints when a binding is missing.
Part 3
A MongoDB client as an eager singleton, closed by an ApplicationLifecycle stop hook. Why sbt run printed nothing until the first request, and why my tests built three clients.
Part 4
A Provider class for the MongoDB client, a @Provides method for the database, and @Named qualifiers for two clocks of the same type, with the real errors Guice prints when I get it wrong.