JavaTM 2 Platform Std. Ed. v1.4.2
- All Implemented Interfaces:
- Guard, Serializable
- Direct Known Subclasses:
- AllPermission, BasicPermission, FilePermission, PrivateCredentialPermission, ServicePermission, SocketPermission, UnresolvedPermission
- public abstract class Permission
- extends Object
- implements Guard, Serializable
Abstract class for representing access to a system resource.
All permissions have a name (whose interpretation depends on the subclass),
as well as abstract functions for defining the semantics of the
particular Permission subclass.
Most Permission objects also include an "actions" list that tells the actions
that are permitted for the object. For example,
java.io.FilePermission object, the permission name is
the pathname of a file (or directory), and the actions list
(such as "read, write") specifies which actions are granted for the
specified file (or for files in the specified directory).
The actions list is optional for Permission objects, such as
that don't need such a list; you either have the named permission (such
as "system.exit") or you don't.
An important method that must be implemented by each subclass is
implies method to compare Permissions. Basically,
"permission p1 implies permission p2" means that
if one is granted permission p1, one is naturally granted permission p2.
Thus, this is not an equality test, but rather more of a
Permission objects are similar to String objects in that they
are immutable once they have been created. Subclasses should not
provide methods that can change the state of a permission
once it has been created.
- See Also:
Constructs a permission with the specified name.
Implements the guard interface for a permission.
Checks two Permission objects for equality.
Returns the actions as a String.
Returns the name of this Permission.
Returns the hash code value for this Permission object.
Checks if the specified permission's actions are "implied by"
this object's actions.
Returns an empty PermissionCollection for a given Permission object, or null if
one is not defined.
Returns a string describing this Permission.
public Permission(String name)
- Constructs a permission with the specified name.
name - name of the Permission object being created.
public void checkGuard(Object object)
- Implements the guard interface for a permission. The
SecurityManager.checkPermission method is called,
passing this permission object as the permission to check.
Returns silently if access is granted. Otherwise, throws
- Specified by:
checkGuard in interface
object - the object being guarded (currently ignored).
SecurityException - if a security manager exists and its
checkPermission method doesn't allow access.
- See Also:
public abstract boolean implies(Permission permission)
- Checks if the specified permission's actions are "implied by"
this object's actions.
This must be implemented by subclasses of Permission, as they are the
only ones that can impose semantics on a Permission object.
implies method is used by the AccessController to determine
whether or not a requested permission is implied by another permission that
is known to be valid in the current execution context.
permission - the permission to check against.
- true if the specified permission is implied by this object,
false if not.
public abstract boolean equals(Object obj)
- Checks two Permission objects for equality.
Do not use the
equals method for making access control
decisions; use the
equals in class
obj - the object we are testing for equality with this object.
- true if both Permission objects are equivalent.
- See Also:
public abstract int hashCode()
- Returns the hash code value for this Permission object.
hashCode behavior for Permission Objects is
- Whenever it is invoked on the same Permission object more than
once during an execution of a Java application, the
must consistently return the same integer. This integer need not
remain consistent from one execution of an application to another
execution of the same application.
- If two Permission objects are equal according to the
method, then calling the
hashCode method on each of the
two Permission objects must produce the same integer result.
hashCode in class
- a hash code value for this object.
- See Also:
public final String getName()
- Returns the name of this Permission.
For example, in the case of a
the name will be a pathname.
- the name of this Permission.
public abstract String getActions()
- Returns the actions as a String. This is abstract
so subclasses can defer creating a String representation until
one is needed. Subclasses should always return actions in what they
consider to be their
canonical form. For example, two FilePermission objects created via
perm1 = new FilePermission(p1,"read,write");
perm2 = new FilePermission(p2,"write,read");
"read,write" when the
getActions method is invoked.
- the actions of this Permission.
public PermissionCollection newPermissionCollection()
- Returns an empty PermissionCollection for a given Permission object, or null if
one is not defined. Subclasses of class Permission should
override this if they need to store their permissions in a particular
PermissionCollection object in order to provide the correct semantics
PermissionCollection.implies method is called.
If null is returned,
then the caller of this method is free to store permissions of this
type in any PermissionCollection they choose (one that uses a Hashtable,
one that uses a Vector, etc).
- a new PermissionCollection object for this type of Permission, or
null if one is not defined.
public String toString()
- Returns a string describing this Permission. The convention is to
specify the class name, the permission name, and the actions in
the following format: '("ClassName" "name" "actions")'.
toString in class
- information about this Permission.
Copyright 2003 Sun Microsystems, Inc. All rights reserved