For a bit of historical context, during this period the Java ecosystem was very heavily into the Service Locator (https://en.wikipedia.org/wiki/Service_locator_

For a bit of historical context, during this period the Java ecosystem was very heavily into the Service Locator (https://en.wikipedia.org/wiki/Service_locator_pattern https://en.wikipedia.org/wiki/Service_locator_pattern) pattern. This meant that your classes would look up their dependencies from the registry at runtime as they needed them, quite often resulting in a runtime error at an indeterminate point if a programmatic error had been made. This also created a bit of a spaghetti nightmare, where it was very hard to reason about which classes (services) were being used by what other services. The Inversion of Control article (later renamed/aliased Dependency Injection) was a reaction to this: it inverted the control away from the using site to the code creating the services. (I appreciate the article does talk about Service Locator, but I think it's worthwhile having an understanding of the normalities of the time when reading it.)