Java in a Nutshell, 5th Edition

Name

ProtectionDomain

Synopsis

This class represents a “protection domain”: the set of permissions associated with code based on its source, and optionally, the identities of the users on whose behalf the code is running. Use the getProtectionDomain( ) of a Class object to obtain the ProtectionDomain that the class is part of.

Prior to Java 1.4, a ProtectionDomain simply associates a CodeSource with the PermissionCollection granted to code from that source by a Policy. The set of permissions is static, and the implies( ) method checks to see whether the specified Permission is implied by any of the permissions granted to this ProtectionDomain.

In Java 1.4 and later, a ProtectionDomain can also be created with the four-argument constructor which associates a PermissionCollection with a ClassLoader and an array of Principal objects in addition to a CodeSource. A ProtectionDomain of this sort represents permisssions granted to code loaded from a specified source, through a specified class loader, and running under the auspices of one or more specified principals. When a ProtectionDomain is instantiated with this four-argument constructor, the PermissionCollection is not static, and the implies( ) method calls the implies( ) method of the current Policy object before checking the specified collection of permissions. This allows security policies to be updated (for example to add new permissions for specific users) without having to restart long-running programs such as servers.

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