Java in a Nutshell, 5th Edition

Name

Permission

Synopsis

This abstract class represents a system resource, such as a file in the filesystem, or a system capability, such as the ability to accept network connections. Concrete subclasses of Permission, such as java.io.FilePermission and java.net.SocketPermission, represent specific types of resources. Permission objects are used by system code that is requesting access to a resource. They are also used by Policy objects that grant access to resources. The AccessController.checkPermission( ) method considers the source of the currently running Java code, determines the set of permissions that are granted to that code by the current Policy, and then checks to see whether a specified Permission object is included in that set. As of Java 1.2, this is the fundamental Java access-control mechanism.

Each permission has a name (sometimes called the target) and, optionally, a comma-separated list of actions. For example, the name of a FilePermission is the name of the file or directory for which permission is being granted. The actions associated with this permission might be “read”; “write”; or “read,write”. The interpretation of the name and action strings is entirely up to the implementation of Permission. A number of implementations support the use of wildcards; for example, a FilePermission can have a name of “/tmp/*”, which represents access to any files in a /tmp directory. Permission objects must be immutable, so an implementation must never define a setName( ) or ...