checkPermission() method.
* Manipulates the access control context for code that needs to be executed
* the protection domain of the calling class (by explicitly ignoring the
* context of the calling code) in the doPrivileged() methods.
* And provides a getContext() method which gives the access
* control context of the current thread that can be used for checking
* permissions at a later time and/or in another thread.
*
* XXX - Mostly a stub implementation at the moment. Needs native support
* from the VM to function correctly. XXX - Do not forget to think about
* how to handle java.lang.reflect.Method.invoke() on the
* doPrivileged() methods.
*
* @author Mark Wielaard (mark@klomp.org)
* @since 1.2
*/
public final class AccessController
{
/**
* This class only has static methods so there is no public contructor.
*/
private AccessController()
{
}
/**
* Checks wether the access control context of the current thread allows
* the given Permission. Throws an AccessControlException
* when the permission is not allowed in the current context. Otherwise
* returns silently without throwing an exception.
*
* @param perm the permission to be checked.
* @exception AccessControlException thrown if the current context does not
* allow the given permission.
*/
public static void checkPermission(Permission perm)
throws AccessControlException
{
getContext().checkPermission(perm);
}
/**
* Calls the run() method of the given action with as
* (initial) access control context only the protection domain of the
* calling class. Calls to checkPermission() in the
* run() method ignore all earlier protection domains of
* classes in the call chain. Note that the protection domains of classes
* called by the code in the run() method are not ignored.
*
* @param action the PrivilegedAction whose run()
* should be be called.
* @returns the result of the action.run() method.
*/
public static Object doPrivileged(PrivilegedAction action)
{
return action.run();
}
/**
* Calls the run() method of the given action with as
* (initial) access control context the given context combined with the
* protection domain of the calling class. Calls to
* checkPermission() in the run() method ignore
* all earlier protection domains of classes in the call chain, but add
* checks for the protection domains given in the supplied context.
*
* @param action the PrivilegedAction whose run()
* should be be called.
* @param context the AccessControlContext whose protection
* domains should be added to the protection domain of the calling class.
* @returns the result of the action.run() method.
*/
public static Object doPrivileged(PrivilegedAction action,
AccessControlContext context)
{
return action.run();
}
/**
* Calls the run() method of the given action with as
* (initial) access control context only the protection domain of the
* calling class. Calls to checkPermission() in the
* run() method ignore all earlier protection domains of
* classes in the call chain. Note that the protection domains of classes
* called by the code in the run() method are not ignored.
* If the run() method throws an exception then this method
* will wrap that exception in an PrivilegedActionException.
*
* @param action the PrivilegedExceptionAction whose
* run() should be be called.
* @returns the result of the action.run() method.
* @exception PrivilegedActionException wrapped around any exception that
* is thrown in the run() method.
*/
public static Object doPrivileged(PrivilegedExceptionAction action)
throws PrivilegedActionException
{
try
{
return action.run();
}
catch (Exception e)
{
throw new PrivilegedActionException(e);
}
}
/**
* Calls the run() method of the given action with as
* (initial) access control context the given context combined with the
* protection domain of the calling class. Calls to
* checkPermission() in the run() method ignore
* all earlier protection domains of classes in the call chain, but add
* checks for the protection domains given in the supplied context.
* If the run() method throws an exception then this method
* will wrap that exception in an PrivilegedActionException.
*
* @param action the PrivilegedExceptionAction whose
* run() should be be called.
* @param context the AccessControlContext whose protection
* domains should be added to the protection domain of the calling class.
* @returns the result of the action.run() method.
* @exception PrivilegedActionException wrapped around any exception that
* is thrown in the run() method.
*/
public static Object doPrivileged(PrivilegedExceptionAction action,
AccessControlContext context)
throws PrivilegedActionException
{
try
{
return action.run();
}
catch (Exception e)
{
throw new PrivilegedActionException(e);
}
}
/**
* Returns the complete access control context of the current thread.
*
* XXX - Should this include all the protection domains in the call chain
* or only the domains till the last doPrivileged() call?
*
* XXX - needs native support. Currently returns an empty context. */ public static AccessControlContext getContext() { // For now just return an new empty context return new AccessControlContext(new ProtectionDomain[0]); } }