- All Implemented Interfaces:
Serializable,Guard
- Direct Known Subclasses:
AllPermission,BasicPermission,CardPermission,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:
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoidcheckGuard(Object object) Implements the guard interface for a permission.abstract booleanChecks twoPermissionobjects for equality.abstract StringReturns the actions as aString.final StringgetName()Returns the name of thisPermission.abstract inthashCode()Returns the hash code value for thisPermissionobject.abstract booleanimplies(Permission permission) Checks if the specified permission's actions are "implied by" this object's actions.Returns an emptyPermissionCollectionfor a givenPermissionobject, ornullif one is not defined.toString()Returns a string describing thisPermission.
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Constructor Details
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Permission
Constructs a permission with the specified name.- Parameters:
name- name of thePermissionobject being created.
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Method Details
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checkGuard
Implements the guard interface for a permission. TheSecurityManager.checkPermissionmethod is called, passing this permission object as the permission to check. Returns silently if access is granted. Otherwise, throws aSecurityException.- Specified by:
checkGuardin interfaceGuard- Parameters:
object- the object being guarded (currently ignored).- Throws:
SecurityException- if a security manager exists and itscheckPermissionmethod doesn't allow access.- See Also:
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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 aPermissionobject.The
impliesmethod is used by the AccessController to determine whether a requested permission is implied by another permission that is known to be valid in the current execution context.- Parameters:
permission- the permission to check against.- Returns:
trueif the specified permission is implied by this object,falseif not.
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equals
Checks twoPermissionobjects for equality.Do not use the
equalsmethod for making access control decisions; use theimpliesmethod. -
hashCode
public abstract int hashCode()Returns the hash code value for thisPermissionobject.The required
hashCodebehavior forPermissionObjects is the following:- Whenever it is invoked on the same
Permissionobject more than once during an execution of a Java application, thehashCodemethod 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
Permissionobjects are equal according to theequalsmethod, then calling thehashCodemethod on each of the twoPermissionobjects must produce the same integer result.
- Whenever it is invoked on the same
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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.
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getActions
Returns the actions as aString. This is abstract so subclasses can defer creating aStringrepresentation 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 thegetActionsmethod is invoked.- Returns:
- the actions of this
Permission.
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newPermissionCollection
Returns an emptyPermissionCollectionfor a givenPermissionobject, ornullif one is not defined. Subclasses of classPermissionshould override this if they need to store their permissions in a particularPermissionCollectionobject in order to provide the correct semantics when thePermissionCollection.impliesmethod is called. Ifnullis returned, then the caller of this method is free to store permissions of this type in anyPermissionCollectionthey choose (one that uses a Hashtable, one that uses a Vector, etc.).- Returns:
- a new
PermissionCollectionobject for this type ofPermission, ornullif one is not defined.
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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 isnullor empty.
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