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MoonLicense

Language-independent Java library for setting/removing license notices

Introduction

License management is an important domain of software development, involving several activities - for example, providing a LICENSE file along with a project, or including copyright notices in source files.

It is fairly evident that such activities must not become boring chores - therefore it is paramount to make them as simple, automated and transparent as possible.

Inspired by great existing open source solutions (License Maven Plugin and License Gradle Plugin), I wanted to create my own tool, tailored to my needs - and so I created MoonLicense.

Supported languages

MoonLicense is a Java library, but its regex-based engine supports a wide variety of languages:

• Java, Scala, Groovy, C, C#, C++, JavaScript and any other language whose long comments are in /* ... */ format

• OCaml, Pascal and other languages whose long comments are in (* ... *) format

• HTML, whose formatter keeps documents compatible with the standard by inserting license notices after the <!DOCTYPE ...> declaration

• XML, whose formatter keeps documents compatible with the standard by inserting license notices after the <?xml...> declaration

Further languages can be easily supported by creating custom formats.

Library architecture

MoonLicense is written in Java, originally to be the kernel of MoonLicense-Gradle - its plugin for Gradle - but it can be used as a full-fledged, standalone library.

Featuring a small set of types, MoonLicense's model is based on the following concepts:

• License: a license, having:

• a name

• a reference URL

• a full template, employed, for example, in LICENSE files

• a notice template, usually employed in source file headers

• NoticeFormat: describes how to format a licence notice in a source code file and how to identify it so as to replace or remove it later

• ProductInfo: product information (e.g.: name, inception year and copyright holder)

• ProductInfoInjector: replaces placeholders within templates (for example, %%%PRODUCT_NAME%%%) with the related information provided by a ProductInfo

• StringNoticeService: sets or removes a license notice within a string - usually the content of a source file - using a given NoticeFormat

• LicensedFileSet: a set of files sharing the same license and product info. The files belonging to the set are described via:

• includes: a map of (regex -> NoticeFormat) entries, each telling which paths will match and the license format to apply

• excludes: a list of regular expressions describing paths to exclude from the set

• TreeNoticeService: employs StringNoticeService to set or remove license notices within every file - matching at least a LicensedFileSet in a given sequence - under a given root directory.

More details on the API can be found in the javadocs.

Regex-based, extensible engine

New languages can be supported just by implementing NoticeFormat, especially by extending DefaultNoticeFormat.

Such custom subclass can be easily plugged into the engine by specifying it as the LicenseFormat of an includes group in a LicensedFileSet.

It is also possible to subclass an existing implementation - such as JavaNoticeFormat - to slightly customize an existing format.

For further information, please refer to the library's javadocs.

Special thanks

Special thanks to great tools which I used a lot and which inspired my work:

• License Maven Plugin
• License Gradle Plugin