001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 * 019 */ 020package org.apache.directory.server.xdbm.search.evaluator; 021 022 023import org.apache.directory.api.ldap.model.entry.Entry; 024import org.apache.directory.api.ldap.model.exception.LdapException; 025import org.apache.directory.api.ldap.model.filter.UndefinedNode; 026import org.apache.directory.server.core.api.partition.PartitionTxn; 027import org.apache.directory.server.xdbm.IndexEntry; 028import org.apache.directory.server.xdbm.search.Evaluator; 029 030 031/** 032 * An Evaluator that always return false, for the case we have no entry to return 033 * 034 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a> 035 */ 036public class EmptyEvaluator implements Evaluator<UndefinedNode> 037{ 038 /** 039 * Create a new instance of the PassThroughEvaluator 040 */ 041 public EmptyEvaluator() 042 { 043 } 044 045 046 /** 047 * {@inheritDoc} 048 */ 049 public boolean evaluate( PartitionTxn partitionTxn, IndexEntry<?, String> indexEntry ) throws LdapException 050 { 051 return false; 052 } 053 054 055 /** 056 * {@inheritDoc} 057 */ 058 public boolean evaluate( Entry entry ) throws LdapException 059 { 060 return false; 061 } 062 063 064 /** 065 * Gets the expression used by this expression Evaluator. 066 * 067 * @return the AST for the expression 068 */ 069 public UndefinedNode getExpression() 070 { 071 return UndefinedNode.UNDEFINED_NODE; 072 } 073 074 075 /** 076 * @see Object#toString() 077 */ 078 public String toString( String tabs ) 079 { 080 StringBuilder sb = new StringBuilder(); 081 082 sb.append( tabs ).append( "EmptyEvaluator\n" ); 083 084 return sb.toString(); 085 } 086 087 088 /** 089 * @see Object#toString() 090 */ 091 public String toString() 092 { 093 return toString( "" ); 094 } 095}