Class Permission
- All Implemented Interfaces:
Serializable
,Guard
- Direct Known Subclasses:
AllPermission
,BasicPermission
,FilePermission
,MBeanPermission
,PrivateCredentialPermission
,ServicePermission
,SocketPermission
,UnresolvedPermission
,URLPermission
Most Permission
objects also include an "actions" list that
tells the actions that are permitted for the object. For example,
for a 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
java.lang.RuntimePermission
,
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
the 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
subset test.
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.
- Since:
- 1.2
- See Also:
-
Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionvoid
checkGuard
(Object object) Implements the guard interface for a permission.abstract boolean
Checks twoPermission
objects for equality.abstract String
Returns the actions as aString
.final String
getName()
Returns the name of thisPermission
.abstract int
hashCode()
Returns the hash code value for thisPermission
object.abstract boolean
implies
(Permission permission) Checks if the specified permission's actions are "implied by" this object's actions.Returns an emptyPermissionCollection
for a givenPermission
object, ornull
if one is not defined.toString()
Returns a string describing thisPermission
.
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Constructor Details
-
Permission
Constructs a permission with the specified name.- Parameters:
name
- name of thePermission
object being created.
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Method Details
-
checkGuard
Implements the guard interface for a permission. Returns silently if access is granted. Otherwise, throws aSecurityException
.- Specified by:
checkGuard
in interfaceGuard
- API Note:
- This method originally threw a
SecurityException
if a security manager was enabled and the requested access, specified by this permission, was not permitted. The Security Manager is no longer supported; thus, this method always throws aSecurityException
. - Parameters:
object
- the object being guarded (currently ignored).- Throws:
SecurityException
- always- See Also:
-
implies
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 aPermission
object.- Parameters:
permission
- the permission to check against.- Returns:
true
if the specified permission is implied by this object,false
if not.
-
equals
Checks twoPermission
objects for equality.Do not use the
equals
method for making access control decisions; use theimplies
method. -
hashCode
public abstract int hashCode()Returns the hash code value for thisPermission
object.The required
hashCode
behavior forPermission
Objects is the following:- Whenever it is invoked on the same
Permission
object more than once during an execution of a Java application, thehashCode
method 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 theequals
method, then calling thehashCode
method on each of the twoPermission
objects must produce the same integer result.
- Whenever it is invoked on the same
-
getName
Returns the name of thisPermission
. For example, in the case of ajava.io.FilePermission
, the name will be a pathname.- Returns:
- the name of this
Permission
.
-
getActions
Returns the actions as aString
. This is abstract so subclasses can defer creating aString
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 the following:perm1 = new FilePermission(p1,"read,write"); perm2 = new FilePermission(p2,"write,read");
both return "read,write" when thegetActions
method is invoked.- Returns:
- the actions of this
Permission
.
-
newPermissionCollection
Returns an emptyPermissionCollection
for a givenPermission
object, ornull
if one is not defined. Subclasses of classPermission
should override this if they need to store their permissions in a particularPermissionCollection
object in order to provide the correct semantics when thePermissionCollection.implies
method is called. Ifnull
is returned, then the caller of this method is free to store permissions of this type in anyPermissionCollection
they choose (one that uses a Hashtable, one that uses a Vector, etc.).- Returns:
- a new
PermissionCollection
object for this type ofPermission
, ornull
if one is not defined.
-
toString
Returns a string describing thisPermission
. The convention is to specify the class name, the permission name, and the actions in the following format: '("ClassName" "name" "actions")', or '("ClassName" "name")' if actions list isnull
or empty.
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