public abstract class Permission extends Object implements Guard, Serializable
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.
Constructs a permission with the specified name.
|Modifier and Type||Method||Description|
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)
name- name of the Permission object being created.
public void checkGuard(Object object) throws SecurityException
SecurityManager.checkPermissionmethod 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).
SecurityException- if a security manager exists and its
checkPermissionmethod doesn't allow access.
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.
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
public abstract int hashCode()
hashCode behavior for Permission Objects is
hashCodemethod 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.
equalsmethod, then calling the
hashCodemethod 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
getActionsmethod is invoked.
public PermissionCollection newPermissionCollection()
PermissionCollection.impliesmethod 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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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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