Friday, July 29, 2016

APIs should be impossible to misuse

It should hard or impossible to misuse a good API
Josh Block
https://www.youtube.com/watch?v=aAb7hSCtvGw

The above statement validates my preference for using the Builder Pattern to facilitate clients to provide named constructor arguments in a sense. E.g. if a constructor has several string parameters, rather than rely on flaky javadocs and parameter names to inform the user what to provide, I would prefer to provide builder methods that unambiguously let the user know what to provide. For validation of inputs, I make the null checks, etc, in the private constructor. That makes it about as hard to misuse the API/constructor as possible in Java.

Thursday, July 28, 2016

Constructor Parameters known only at Runtime

it's assumed here that your Factory knows what the parameters for the constructors should be. If this is only known by the client of the Create method, then I would say the indirection isn't necessary and the client should construct the rule itself
http://stackoverflow.com/a/23765599

So, Factory Pattern may not be appropriate when the constructor parameters need to be provided by the client.

As for "DI abuse," see http://stackoverflow.com/a/1056229 on direct instantiation rather than injection of stateless services:
The abuse of DI leads to stateless objects which really should be stateful ... such code is by nature domain/use-case specific. In such a case ... it makes much more sense to have the [client] directly instantiate the business service class, passing data provided by the user through a constructor

Sunday, July 17, 2016

Abstract Factory and "DI Explosion"

On the problem of creating objects from both stateless services and runtime values, Mark Seemann suggests the standard Abstract Factory pattern while seeming to acknowledge that it may be overkill for simple cases (i.e. say we have a lot of these objects to create, e.g. subclasses of say HystrixCommand, do we really want to create a Factory implementation for each subclass?)

Yes I know this, though in my case I hesitate because for simple cases it's overkill to duplicate constructor with interface, factory, factory's constructor, Create method, etc. While good for complex cases, it's too "DI explosion" for simple things I think. And the question remains about automatic registration DI container. – queen3 Nov 6 '09 at 11:16 @queen3: I understand what you mean, but I'm not aware of any DI Containers that can do what you ask.
http://stackoverflow.com/questions/1686760/which-di-container-will-satisfy-this/1686887#1686887

Saturday, July 16, 2016

The Pareto Principle applied in Spring JDBC

The Pareto Principle in action: going the extra mile to automate the extraction process makes the framework much more complex and delivers little real benefit
http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/jdbc/object/MappingSqlQueryWithParameters.html

Here the Pareto Principle (or 80/20 rule) is applied via this Spring JDBC mapper.

I would argue that this notion should be considered before embarking on any major automation project, e.g. writing a framework to automate the generation of forms and form fields rather then writing static views.