Before exploring the CDI, let's use a very simple example (I would say, a handmade example) to illustrate what a bean container is.
We will use an application that has TimeService, which simply provides a now() method returning the current LocalDateTime.
Here is what it can look like in terms of code:
public interface TimeService { LocalDateTime now();}
A trivial implementation will rely on the native now() implementation:
public class TimeServiceImpl implements TimeService { @Override public LocalDateTime now() { return LocalDateTime.now(); }}
But you may also need to be able to switch to a mock (for tests or another customer, for instance):
public class MockTimeService implements TimeService { @Override public ...
