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Showing posts with the label Separation of Concerns

Make Our Code More Testable with Proxy Design Pattern

If you heard about the term separation of concerns, you could agree this concept is very important for making a system "clean". One of the most important characteristics of a clean system is testable.

Let me tell you my story about how I've just come acrosss the design pattern Proxy.

Note: to get started, you can find a very simple example of the pattern Proxy here
Let's start! I have an interface as below:
public interface DocumentGenerator { File generate(Document document) throws BusinessException; }
The following is my first implementation for a concrete class of DocumentGenerator.
public class DocumentGeneratorImpl implements DocumentGenerator { private Dossier dossier; private Locale locale; public DocumentGeneratorImpl(Dossier dossier, Locale locale) { validateNotNullParams(dossier, locale); this.dossier = dossier; this.locale = locale; } private void validateNotNullParams(LibertyDossier dossier, Locale locale) { if(Objects.isNull(dossier…

Separate Constructing a System from Using It

In the real world, in order to use a building (hotel, supermarket, etc) we need to construct it first. This concern should be applied for software development as well.

Step by step, I would like to show you the issue about no separation of constructing and using it and then I'll give you some approaches to overcome this issue.

| Note: you can find the below demonstrated code here
Take a Look the Following Simple ApplicationUsed tools and technologies: Eclipse (Mars), JDK 1.8

I had an App which uses Controller. Controller uses Service (an interface). Finally, Service has one concrete class is DefaultService.
//package vn.nvanhuong.system.separationconstructing; public class App { public static void main(String[] args) { Controller controller = new Controller(); controller.doAction(); } } public class Controller { private Service service; public void doAction(){ System.out.println("doAction in Controller"); getService().execute(); } public Service getServi…