List JARs on the classpath that export a given package

Summary

The exporters macro returns a comma-separated list of JAR names from the classpath that contain (export) a specified package. This is useful for discovering which dependencies provide a particular package.

Syntax 

${exporters;<package-name>}

Parameters

  • package-name - The fully qualified package name (e.g., “com.example.api”)

Behavior

  • Searches all JARs on the build classpath
  • Checks each JAR for directories matching the specified package
  • Returns a comma-separated list of JAR names that contain the package
  • Package name uses dot notation (e.g., “com.example”) which is converted internally to path format
  • Returns empty string if no JARs export the package

Examples

Find which JARs provide a specific package:

slf4j.jars=${exporters;org.slf4j}
# Returns: "slf4j-api-1.7.30"

Check if a package is available:

${if;${exporters;javax.servlet};servlet-available;servlet-missing}

List providers of multiple packages:

json.providers=${exporters;org.json}
jackson.providers=${exporters;com.fasterxml.jackson.core}

Document dependencies:

# Package javax.xml.bind provided by: ${exporters;javax.xml.bind}

Use Cases

  • Discovering which dependencies provide specific packages
  • Debugging classpath and dependency issues
  • Documenting package sources
  • Conditional configuration based on available packages
  • Validating that required packages are on the classpath
  • Analyzing dependency conflicts

Notes

  • Only searches JARs on the build classpath (not runtime classpath)
  • Package name should use dot notation (e.g., “org.osgi.framework”)
  • Returns JAR filenames, not full paths
  • Multiple JARs may export the same package (split packages)
  • Empty return value indicates the package is not found on the classpath

See test cases in MacroTestsForDocsExamples.java