Class Permission

java.lang.Object
java.security.Permission
All Implemented Interfaces:
Serializable,Guard
Direct Known Subclasses:
AllPermission,BasicPermission,CardPermission,FilePermission,MBeanPermission,PrivateCredentialPermission,ServicePermission,SocketPermission,UnresolvedPermission,URLPermission
public abstract classPermissionextendsObjectimplementsGuard,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.

MostPermission objects also include an "actions" list that tells the actions that are permitted for the object. For example, for ajava.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 forPermission objects, such asjava.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 theimplies 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 toString 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 Details

    • Permission

      public Permission(String name)
      Constructs a permission with the specified name.
      Parameters:
      name - name of thePermission object being created.

  • Method Details

    • checkGuard

      public void checkGuard(Object object) throwsSecurityException
      Implements the guard interface for a permission. Returns silently if access is granted. Otherwise, throws aSecurityException.
      Specified by:
      checkGuard in interface Guard
      API Note:
      This method originally threw aSecurityException 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

      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 ofPermission, 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

      public abstract boolean equals(Object obj)
      Checks twoPermission objects for equality.

      Do not use theequals method for making access control decisions; use theimplies method.

      Overrides:
      equals in class Object
      Parameters:
      obj - the object we are testing for equality with this object.
      Returns:
      true if bothPermission objects are equivalent.
      See Also:

    • hashCode

      public abstract int hashCode()
      Returns the hash code value for thisPermission object.

      The requiredhashCode behavior forPermission Objects is the following:

      • Whenever it is invoked on the samePermission 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 twoPermission objects are equal according to theequals method, then calling thehashCode method on each of the twoPermission objects must produce the same integer result.

      Overrides:
      hashCode in class Object
      Returns:
      a hash code value for this object.
      See Also:

    • getName

      public final String 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 thisPermission.

    • getActions

      public abstract String 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 thisPermission.

    • newPermissionCollection

      public PermissionCollection 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 newPermissionCollection object for this type ofPermission, ornull if one is not defined.

    • toString

      public String 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.
      Overrides:
      toString in class Object
      Returns:
      information about thisPermission.