Component finder

The Structurizr for Java library includes a component finder and a number of prebuilt pluggable strategies that allow you to extract components from a codebase.

Background

The idea behind the C4 model and Structurizr is that there are a number of levels of abstraction sitting above the code. Although we write Java code using interfaces and classes in packages, it's often useful to think about how that code is organised into "components". In its simplest form, a "component" is just a grouping of classes and interfaces.

If you reverse-engineer some Java code using a UML tool, you'll typically get a UML class diagram showing all of the classes and interfaces. The component diagram in the C4 model is about hiding some of this complexity and implementation detail. You can read more about this at Components vs classes.

Purpose

The purpose of the component finder is to find components in your codebase. Since every codebase is different (i.e. code structure, naming conventions, frameworks used, etc), different pluggable component finder strategies allow you to customize the rules that you use to find components. Some example rules that you might use to find components include:

All classes where the name ends with Component.
All classes where the name ends with Controller.
All classes that are annotated with the Spring @Repository annotation.
All classes that inherit from AbstractComponent.
etc

Basic usage

To use a component finder, simply create an instance of the ComponentFinder class and configure it as needed.

Container webApplication = mySoftwareSystem.addContainer("Web Application", "Description", "Apache Tomcat 7.x");

ComponentFinder componentFinder = new ComponentFinder(
    webApplication, "com.mycompany.mysoftwaresystem",
    ... a number of component finder strategies ...);
componentFinder.findComponents();

In this case, we're going to find components and associate them with the webApplication container, and we're only going to find components that reside somewhere underneath the com.mycompany.mysoftwaresystem package to avoid accidentally finding components residing in frameworks that we might be using.

We also need to plug in one or more component finder strategies, which actually implement the logic to find and extract components from a codebase.