关于Groovy CliBuilder依赖及内置groovyjarjarcommonscli包的疑问

Great question—this is a common point of confusion with Groovy's handling of third-party dependencies, so let's break it down clearly.

Why isn't Apache commons-cli included in groovy-all directly? #

Groovy doesn't include the official org.apache.commons.cli package in groovy-all because it uses a technique called jarjar repackaging to avoid classpath conflicts. Many Java/Groovy projects already depend on commons-cli, and different versions of the library can cause runtime errors if they collide on the classpath. To solve this, Groovy takes the commons-cli code, renames its package to groovyjarjarcommonscli, and includes this repackaged version internally in groovy-all.

Your Three Follow-Up Questions #

1. Why does Groovy include the repackaged groovyjarjarcommonscli package? #

As mentioned above, the core reason is dependency conflict prevention. By repackaging commons-cli under a Groovy-specific package name, Groovy ensures its internal use of commons-cli doesn't interfere with any version of commons-cli your project might already depend on. This is a standard practice in many libraries to isolate their internal dependencies from user projects.

2. Why doesn't Groovy's CliBuilder use this repackaged package? #

Actually, it does! Groovy's groovy.util.CliBuilder is built directly on top of the internal groovyjarjarcommonscli classes. The confusion likely comes from two places:

• If your code directly imports org.apache.commons.cli classes (instead of just using CliBuilder's API), you'll get missing class errors because groovy-all doesn't include the official package.
• Older documentation might reference underlying commons-cli concepts, but you never need to interact with the official package when using CliBuilder properly.

3. Can I depend on the internal groovyjarjarcommonscli package in the future? #

No, you shouldn't rely on this package. It's strictly an internal implementation detail of Groovy. The repackaged package name and its contents are not part of Groovy's public API, meaning Groovy maintainers could rename it, modify its code, or remove it entirely in future versions without warning. If you need to use commons-cli features directly, add the official Apache commons-cli dependency to your project explicitly instead.

内容的提问来源于stack exchange，提问作者wu-lee