New module added to Principle

I've added a new module to JPrinciple recently to enable the developer to constrain access to third party libraries to designated parts of the code. The reason for this is that I sometimes see processing json in app layer or using the Mongo API from the domain in our codebase. Being an ardent DDD proponent, I just cannot have that happening again! So the idea is that you can specify which libraries you allow access to in which layer. All the layers around the specified one can use those libraries of course, but nothing under it. Hope it made some sense. Probably it's better to see through an example

	<build>
	<plugins>
	<plugin>
	<groupId>org.tindalos.principle</groupId>
	<artifactId>principle</artifactId>
	<version>0.25</version>
	<configuration>
	<basePackage>org.tindalos.principle</basePackage>
	<checks>
	<layering>
	<layers>
	<param>infrastructure</param>
	<param>app</param>
	<param>domain</param>
	</layers>
	<violationsThreshold>0</violationsThreshold>
	</layering>
	<thirdParty>
	<barriers>
	<barrier>
	<layer>infrastructure</layer>
	<components>org.apache.maven,org.json,org.yaml,com.google.common.collect,jdepend</components>
	</barrier>
	<barrier>
	<layer>domain</layer>
	<components>org.apache.commons</components>
	</barrier>
	</barriers>
	<violationsThreshold>0</violationsThreshold>
	</thirdParty>
	...
	</plugin>
	...
	</plugins>
	...
	</build>

view raw Principle_ThirdParty.xml hosted with ❤ by GitHub

The new part is the <thirdparty>...</thirdparty>. It says that anything under org.apache.commons can be referenced in the Domain layer and up (app and infrastrucure), and the Infrastructure layer can use anything under the listed package paths: org.apache.maven,org.json,org.yaml,com.google.common.collect,jdepend. Anything else used in Infrastructure, e.g. something under org.mongo, would cause an alert. So would the reference to org.json in Domain, since it's only allowed in Infrastructure.
The visual idea behind it is that your code is a castle with multiple circles of defending walls around it. You let foreign troops leaking into your territory only until certain walls. Different troops can have different privileges, one (org.yaml) can only set up his tent inside the outmost wall (Infrastructure), the other (org.apache.commons) is allowed to enter the inner sanctum (Domain). Usable from version 0.25.