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JavaTM 2 Platform Standard Edition |
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java.lang.Object | +--java.security.Permission
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,
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.
Permissions
,
PermissionCollection
, Serialized FormConstructor Summary | |
Permission(String name)
Constructs a permission with the specified name. |
Method Summary | |
void |
checkGuard(Object object)
Implements the guard interface for a permission. |
abstract boolean |
equals(Object obj)
Checks two Permission objects for equality. |
abstract String |
getActions()
Returns the actions as a String. |
String |
getName()
Returns the name of this Permission. |
abstract int |
hashCode()
Returns the hash code value for this Permission object. |
abstract boolean |
implies(Permission permission)
Checks if the specified permission's actions are "implied by" this object's actions. |
PermissionCollection |
newPermissionCollection()
Returns an empty PermissionCollection for a given Permission object, or null if one is not defined. |
String |
toString()
Returns a string describing this Permission. |
Methods inherited from class java.lang.Object |
clone,
finalize,
getClass,
notify,
notifyAll,
wait,
wait,
wait |
Constructor Detail |
public Permission(String name)
name
- name of the Permission object being created.Method Detail |
public void checkGuard(Object object) throws SecurityException
SecurityManager.checkPermission
method is called,
passing this permission object as the permission to check.
Returns silently if access is granted. Otherwise, throws
a SecurityException.object
- the object being guarded (currently ignored).checkPermission
method doesn't allow access.Guard
,
GuardedObject
,
SecurityManager.checkPermission(java.security.Permission)
public abstract boolean implies(Permission permission)
This must be implemented by subclasses of Permission, as they are the only ones that can impose semantics on a Permission object.
The 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.public abstract boolean equals(Object obj)
Do not use the equals
method for making access control
decisions; use the implies
method.
obj
- the object we are testing for equality with this object.public abstract int hashCode()
The required hashCode
behavior for Permission Objects is
the following:
hashCode
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.
equals
method, then calling the hashCode
method on each of the
two Permission objects must produce the same integer result.
public final String getName()
java.io.FilePermission
,
the name will be a pathname.public abstract String getActions()
perm1 = new FilePermission(p1,"read,write"); perm2 = new FilePermission(p2,"write,read");both return "read,write" when the
getActions
method is invoked.public PermissionCollection newPermissionCollection()
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).public String toString()
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JavaTM 2 Platform Standard Edition |
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