find_unreferenced_classes.txt

Advanced example usage of JavaClass::Classpath::TrackingClasspath. Load all classes of an Eclipse workspace. Then mark all referenced classes. In the end report remaining classes as unreferenced. This lists potential unused classes. Note that the classes may still be used by reflection. Also this can be used to find classes that have a certain number of references to them, e.g. only used once.

Author:	Peter Kofler
Copyright:	Copyright (c) 2009, Peter Kofler.
License:	BSD License

Steps

 require 'javaclass/dsl/mixin'
 require 'javaclass/classpath/tracking_classpath'

speed up loading by skipping non source file classpaths

 Eclipse.skip_lib

1) create the (tracking) composite classpath of the given workspace

 cp = workspace(location)
 puts "#{cp.elements.size} classpaths found under the workspace #{location}:"
 puts "  #{cp.elements.join("\n  ")}"

create a filter to limit all operations to the classes of two base packages

 filter = Proc.new { |clazz| clazz.same_or_subpackage_of?(package1) ||
                             clazz.same_or_subpackage_of?(package2) }

2) load all classes in the given packages

 puts 'loading all *filtered* classes... (can take several minutes)'
 classes = cp.values(&filter)
 puts "#{classes.size} classes loaded from classpaths"

3) mark all referenced types in the given packages as accessed

 cp.reset_access
 classes.map { |clazz| clazz.imported_types }.
         flatten.
         find_all(&filter).
         each { |classname| cp.mark_accessed(classname) }
 puts '*filtered* classes mapped'

4) also mark all classes referenced from config files (e.g. hardcoded class names)

 hardcoded_classnames = scan_config_for_3rd_party_class_names(location).find_all(&filter)
 puts "#{hardcoded_classnames.size} classes references found in configs"
 hardcoded_classnames.each { |classname| cp.mark_accessed(classname) }
 puts 'hardcoded classes mapped'

5) mark unit tests (all classes ending in Test) on the test projects (classpath elements ending in .test)

 test_projects = cp.elements.find_all { |cpe| cpe.to_s =~ /\.test\// }
 test_projects.each do |project|
   project.names { |classname| classname =~ /Test(?:Case|Suite|s)?\.class/ }.
           each { |classname| project.mark_accessed(classname) }
 end
 puts 'test classes mapped'

6) find non accessed classes in specific packages and report them

 unused_classes = classes.find_all { |clazz| cp.accessed(clazz) == 0 }
 report = unused_classes.map { |clazz| "#{clazz.to_classname}" }
 puts "#{report.size} unused classes found:\n  #{report.join("\n  ")}"

7) find only once accessed classes and report them

 once_used_classes = classes.find_all { |clazz| cp.accessed(clazz) == 1 }
 report = once_used_classes.map { |clazz| "#{clazz.to_classname}" }
 puts "#{report.size} once used classes found:\n  #{report.join("\n  ")}"

 twice_used_classes = classes.find_all { |clazz| cp.accessed(clazz) == 2 }
 report = twice_used_classes.map { |clazz| "#{clazz.to_classname}" }
 puts "#{report.size} twice used classes found:\n  #{report.join("\n  ")}"