Project Jigsaw: VM changes for Modules

2009/2/3

Classloading

5.3.5 Deriving a Class from a class File Representation

Only members of a class in a module may use module accessibility

By the definition of ACC_MODULE in chapter 4, a ClassFormatError must be thrown if a ClassFile uses the ACC_MODULE flag in ClassFile.access_flags, field_info.access_flags, method_info.access_flags or InnerClasses.inner_class_access_flags, and the ClassFile does not have a Module attribute.

Resolution

5.4.3.4 Interface method resolution

When resolving an interface method reference:

If C is not an interface, interface method resolution throws an IncompatibleClassChangeError.
Otherwise, if the referenced method does not have the same name and descriptor as a method in C or in one of the superinterfaces of C, or in class Object, interface method resolution throws a NoSuchMethodError.
Otherwise, if the referenced method is not accessible (§5.4.4) to D, interface method resolution throws an IllegalAccessError.

5.4.4 Access Control

Terminology:

A class's runtime module is the pair of its module name and defining classloader.

TODO: Add discussive text about VM's use of classloaders

A class or interface C is accessible to a class or interface D if and only if any of the following conditions are true:

C is public.
C is module and D is a member of the same runtime module as C.
C and D are members of the same runtime package (5.3).

A field or method R is accessible to a class or interface D if and only if any of the following conditions is true:

R is public.
R is module and is declared in a class C, and D is a member of the same runtime module as C.
R is protected and is declared in a class C, and D is either a subclass of C or C itself. Furthermore, if R is not static, then the symbolic reference to R must contain a symbolic reference to a class T, such that T is either a subclass of D, a superclass of D or D itself.
R is either protected or has default access (that is, neither public nor module nor protected nor private), and is declared by a class in the same runtime package as D.
R is private and is declared in D.

Other JVMS changes

4.2.1 Binary class and interface names
4.3.2 Field descriptors