Summary

Enable code to assert a subset of its privileges without otherwise preventing the full access-control stack walk to check for other permissions.

Motivation

This is very useful when you need to enable some permissions while allowing others to continue the stack walk.

Description

Add a java.security.AccessController.doPrivileged method that takes a permission argument.

For example, some bootstrap JRE code could assert a privilege to GET a configuration file via http:

AccessController.doPrivileged(anon class...,
                              new URLPermission(url,
                                                request props ...,
                                                "GET") ...

A checkPermission() for a matching URLPermission (done by the http handler) would stop walking the access-control context (acc) stack at that doPrivileged() invocation and succeed. A check for a non-matching URLPermission or some other permission, however, would match the JRE class's generally assigned privileges and continue walking the full acc stack as if the limited doPrivileged() had not been invoked.

These limited privileges are also captured by getAccessControlContext() and by thread inheritance.