The most important method in this class is implies. This
* checks whether if one has this permission, then the specified
* permission is also implied. As a conceptual example, consider the
* permissions "Read All Files" and "Read File foo". The permission
* "Read All Files" implies that the caller has permission to read the
* file foo.
*
*
Permission's must be immutable - do not change their
* state after creation.
*
* @author Aaron M. Renn (arenn@urbanophile.com)
* @see Permissions
* @see PermissionCollection
* @since 1.1
* @status updated to 1.4
*/
public abstract class Permission implements Guard, Serializable
{
/**
* Compatible with JDK 1.1+.
*/
private static final long serialVersionUID = -5636570222231596674L;
/**
* This is the name assigned to this permission object.
*
* @serial the name of the permission
*/
private String name;
/**
* Create an instance with the specified name.
*
* @param name the permission name
*/
public Permission(String name)
{
this.name = name;
}
/**
* This method implements the Guard interface for this class.
* It calls the checkPermission method in
* SecurityManager with this Permission as its
* argument. This method returns silently if the security check succeeds
* or throws an exception if it fails.
*
* @param obj the Object being guarded - ignored by this class
* @throws SecurityException if the security check fails
* @see GuardedObject
* @see SecurityManager#checkPermission(Permission)
*/
public void checkGuard(Object obj)
{
SecurityManager sm = System.getSecurityManager();
if (sm != null)
sm.checkPermission(this);
}
/**
* This method tests whether this Permission implies that the
* specified Permission is also granted.
*
* @param perm the Permission to test against
* @return true if perm is implied by this
*/
public abstract boolean implies(Permission perm);
/**
* Check to see if this object equals obj. Use implies, rather
* than equals, when making access control decisions.
*
* @param obj the object to compare to
*/
public abstract boolean equals(Object obj);
/**
* This method returns a hash code for this Permission. It
* must satisfy the contract of Object.hashCode: it must be
* the same for all objects that equals considers to be the same.
*
* @return a hash value
*/
public abstract int hashCode();
/**
* Get the name of this Permission.
*
* @return the name
*/
public final String getName()
{
return name;
}
/**
* This method returns the list of actions for this Permission
* as a String. The string should be in canonical order, for
* example, both new FilePermission(f, "write,read") and
* new FilePermission(f, "read,write") have the action list
* "read,write".
*
* @return the action list for this Permission
*/
public abstract String getActions();
/**
* This method returns an empty PermissionCollection object
* that can store permissions of this type, or null if no
* such collection is defined. Subclasses must override this to provide
* an appropriate collection when one is needed to accurately calculate
* implies.
*
* @return a new PermissionCollection
*/
public PermissionCollection newPermissionCollection()
{
return null;
}
/**
* This method returns a String representation of this
* Permission object. This is in the format:
* '(' + getClass().getName() + ' ' + getName() + ' ' + getActions
* + ')'.
*
* @return this object as a String
*/
public String toString()
{
return '(' + getClass().getName() + ' ' + getName() + ' '
+ getActions() + ')';
}
} // class Permission