src/org/apache/osgi/framework/util/ldap/Unknown.java

/*
 *   Copyright 2005 The Apache Software Foundation
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 *
 */
package org.apache.osgi.framework.util.ldap;

/**
 * This class is used to create simple marker instances that are inserted
 * into the evaluation stack of a LDAP filter expression when an attribute
 * is referenced that has no defined value. These invalid marker instances
 * force the operators to throw an "unsupported type" exception, which the
 * evaluator catches and then converts the entire subexpression containing
 * the non-existent attribute to <tt>false</tt>.
**/
class Unknown
{
}