protected ControlFactory() 
{

}

 abstract public Control getControlInstance(Control ctl) throws NamingException
Creates a control using this control factory.

The factory is used by the service provider to return controls
that it reads from the LDAP protocol as specialized control classes.
Without this mechanism, the provider would be returning
controls that only contained data in BER encoded format.

Typically, ctl is a "basic" control containing
BER encoded data. The factory is used to create a specialized
control implementation, usually by decoding the BER encoded data,
that provides methods to access that data in a type-safe and friendly
manner.

For example, a factory might use the BER encoded data in
basic control and return an instance of a VirtualListReplyControl.

If this factory cannot create a control using the argument supplied,
it should return null.
A factory should only throw an exception if it is sure that
it is the only intended factory and that no other control factories
should be tried. This might happen, for example, if the BER data
in the control does not match what is expected of a control with
the given OID. Since this method throws NamingException,
any other internally generated exception that should be propagated
must be wrapped inside a NamingException.

 public static Control getControlInstance(Control ctl,
    Context ctx,
    Hashtable env) throws NamingException 
{
        // Get object factories list from environment properties or
        // provider resource file.
        FactoryEnumeration factories = ResourceManager.getFactories(
            LdapContext.CONTROL_FACTORIES, env, ctx);
        if (factories == null) {
            return ctl;
        }
        // Try each factory until one succeeds
        Control answer = null;
        ControlFactory factory;
        while (answer == null && factories.hasMore()) {
            factory = (ControlFactory)factories.next();
            answer = factory.getControlInstance(ctl);
        }
        return (answer != null)? answer : ctl;
}

Creates a control using known control factories.

The following rule is used to create the control:

• Use the control factories specified in the LdapContext.CONTROL_FACTORIES property of the environment, and of the provider resource file associated with ctx, in that order. The value of this property is a colon-separated list of factory class names that are tried in order, and the first one that succeeds in creating the control is the one used. If none of the factories can be loaded, return ctl. If an exception is encountered while creating the control, the exception is passed up to the caller.

Note that a control factory must be public and must have a public constructor that accepts no arguments.