1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, 13 * software distributed under the License is distributed on an 14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 15 * KIND, either express or implied. See the License for the 16 * specific language governing permissions and limitations 17 * under the License. 18 * 19 */ 20 package org.apache.directory.server.xdbm.search; 21 22 23 import org.apache.directory.shared.ldap.filter.ExprNode; 24 import org.apache.directory.server.xdbm.IndexEntry; 25 26 27 /** 28 * Evaluates candidate entries to see if they match a filter expression. 29 * 30 * Evaluators contain various overloads to the evaluate method. Often a 31 * developer working in this region of the code may wonder when to use one 32 * override verses another. The overload taking an IndexEntry argument is 33 * specifically suited for use when there is the possibility of multiple entry 34 * lookups from the master table. If the same candidate in the form of an 35 * IndexEntry is evaluated more then this overload is more efficient since it 36 * stores the looked up entry in the IndexEntry preventing multiple lookups. 37 * 38 * If the index entry is already populated with an entry object, and some 39 * evaluation is required then it is preferrable to use the overload that 40 * takes a Long id instead. Likewise if it is known in advance that the 41 * expression is a leaf node built on an indexed attribute then the overload 42 * with the Long id argument is also preferrable unless an IndexEntry already 43 * exists in which case it makes no difference. 44 * 45 * The overload taking the ServerEntry itself is a last resort option and ok 46 * to use when it is known that no index exists for the attributes of 47 * Evaluators based on leaf expressions. 48 * 49 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a> 50 * @version $Rev: 656489 $ 51 */ 52 public interface Evaluator<N extends ExprNode,E> 53 { 54 /** 55 * Evaluates a candidate to determine if a filter expression selects it. 56 * If an IndexEntry does has a null reference to the entry object, this 57 * Evaluator may set it if it has to access the full entry within the 58 * master table of the store. Subsequent evaluations on the IndexEntry 59 * then need not access the store to retreive the entry if they need to 60 * access it's attributes. 61 * 62 * @param entry the index record of the entry to evaluate 63 * @return true if filter selects the candidate false otherwise 64 * @throws Exception if there are faults during evaluation 65 */ 66 boolean evaluate( IndexEntry<?, E> entry ) throws Exception; 67 68 69 /** 70 * Evaluates whether or not a candidate, specified by an id, satisfies the 71 * expression associated with this Evaluator . 72 * 73 * @param id the identifier for the candidate entry 74 * @return true if filter selects the candidate false otherwise 75 * @throws Exception if there are faults during evaluation 76 */ 77 boolean evaluate( Long id ) throws Exception; 78 79 80 /** 81 * Evaluates whether or not a candidate, satisfies the expression 82 * associated with this Evaluator . 83 * 84 * @param entry the candidate entry 85 * @return true if filter selects the candidate false otherwise 86 * @throws Exception if there are faults during evaluation 87 */ 88 boolean evaluate( E entry ) throws Exception; 89 90 91 /** 92 * Gets the expression used by this expression Evaluator. 93 * 94 * @return the AST for the expression 95 */ 96 N getExpression(); 97 }