OO Design is more about ‘Doing’ than ‘Being’

One of the most profound insights I have learnt about OO is that class design — the shaping of classes & types — is best informed by what processing needs to do, rather than the ‘kind’ of entities it goes between.

What we are talking about here is behavior, rather than trying to categorize entities at rest. Program code only acts by being executed; classes & interfaces (types) are a mechanism to despatch that execution to specific methods.

This shows that OO is really about active behavior, rather than any other arbitrary notions of classification.

But shouldn’t inheritance just follow Entity Properties?

At this point, we’ll address a common interjection — what about bean-style entities, and their properties? Surely inheritance should just follow these! Continue reading

‘Advanced OO Design’ series

Real software sees entities (Customer, File etc) involved in multiple interactions. Simple OO examples model behavior in entity classes directly, but this becomes tangled as behaviors & interactions increase; and results in broken inheritance structures.

Instead of modelling these all in the entity, a more advanced OO approach considers separating behavior from the entity. We’ll consider key principles in this multi-part series. Continue reading

Value Types & List<int> coming for Java 10 ?

Oracle, with lead engineer Brian Goetz, have launched an experimental OpenJDK project to bring long-awaited features to the Java platform.

Major enhancements to generics & new ‘value types’ are planned. Highlights include:

  • Value Types;  highly-efficient small ‘objects’ without inheritance.
  • Reified Generics;  retaining their actual type at runtime.
  • Generic Specialization;  List<int> would be valid & highly efficient.
  • ‘volatile’ enhancements.

The effort is named Project Valhalla. Here’s a preview: Continue reading

Explicit vs Implicit configuration in Spring

With the move to annotations for use of Spring, many projects have become based on component-scanning, auto-wiring and property-placeholder injection — an ‘implicit’ approach to configuration.

However, it can still be very useful to specify ‘explicit’ configuration. This gives us control of top-level application config & enables extensible configuration using the Strategy pattern.

Gaining control of configuration is crucial to enable per-customer/ per-application customization. Continue reading