doclets

Doclets are plug-ins for documentation generation tools that control how documentation data is collected, organized, and presented. The term is most closely associated with the Javadoc tool used in the Java ecosystem.

In Java, a doclet processes information extracted from source code and Javadoc comments and outputs documentation in a chosen format. The standard Javadoc doclet generates HTML pages for packages, classes, methods, and fields. Custom doclets can export to other formats such as XML, Markdown, or PDF, or they can reorganize content, modify navigation, or apply different styling and structure to the output.

Implementation typically involves creating a class that implements the Doclet API and registering it with the Javadoc tool via command-line options such as -doclet and -docletpath. Modern Javadoc doclets interact with a DocletEnvironment that exposes the program structure and comments. Earlier approaches used the older com.sun.javadoc.Doclet API, which has been superseded by the standardized API in recent Java versions.

Common use cases include generating API references in non-HTML formats for integration with content management systems, static site generators, or internal documentation pipelines, as well as applying custom formatting or filtering to match organizational requirements.

Doclets are part of a broader ecosystem of Javadoc extensions, including taglets for handling custom Javadoc tags. They require attention to API compatibility across Java releases, since the underlying tooling and interfaces evolve over time.