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javamavendependenciespackage

Possible to enforce package dependency hierarchy in Java?

Basically I have packages...

com.me.application
com.me.application.thing
com.me.library

I want to enforce the rule that nothing in com.me.application can include com.me.library, except things in com.me.application.thing.

Is this possible at the level of Java code, Maven, classpath, or any other layer of Java that would be roughly equivalent to linking in C?

Solution

  • The only way that I can think of is through AspectJ.

    AspectJ is an aspect oriented language, that is used to add cross-cutting concerns into your application through a separate compile process. One of the classical uses of AspectJ is policy enforcement, which fits your scenario.

    Basically you declare rules that decide from which package which code may be called and throw a compile error whenever you encounter a method call (or in your case a variable declaration) that violates these rules. You can learn the details in the excellent book AspectJ in Action

    AspectJ can nicely be integrated into a Maven build through the AspectJ plugin

    And if you use AspectJ only for policy enforcement, you won't have any additional runtime dependencies, as your byte code won't be modified.