1 Nasgen is a tool for processing Java classes that implement native
   2 JavaScript objects. It does so by looking for the
   3 com.oracle.nashorn.objects.annotations.ScriptClass annotation and other
   4 annotations in that package.
   5 
   6 For each  class "C", nasgen instruments the original class and generates
   7 two additional classes: a "C$Prototype" class for the JavaScript
   8 prototype object, and a "C$Constructor" class for the JavaScript
   9 constructor function.
  10 
  11 Each class instrumented or generated by nasgen contains a private static
  12 "$nasgenmap$" field of type com.oracle.nashorn.runtime.PropertyMap and
  13 static initializer block to initialize the field to the object's
  14 JavaScript properties.
  15 
  16 Members annotated with @Function, @Property, @Getter, and @Setter are
  17 mapped to the $Constructor, $Prototype, or main class, depending on the
  18 value of the annotation's 'where' field. By default, @Property, @Getter,
  19 and @Setter belong to the main class while @Function methods without
  20 explicit 'where' field belong to the $Prototype class. The @Constructor
  21 annotation marks a method to be invoked as JavaScript constructor.
  22 
  23 Nasgen enforces all @Function/@Getter/@Setter/@Constructor annotated
  24 methods to be declared as static. Static final @Property fields remain
  25 in the main class while other @Property fields are moved to respective
  26 classes depending on the annotation's 'where' value. For functions
  27 mapped to the $Prototype or $Constructor class, nasgen also generates
  28 getters and setters prefixed by G$ and S$, respectively.
  29 
  30 Nasgen-generated classes are hidden from normal ClassLoaders by giving
  31 them a ".clazz" file name extension instead of the standard ".class"
  32 extension. This allows script classes to be loaded independently by each
  33 Nashorn context through the com.oracle.nashorn.runtime.StructureLoader
  34 class loader.