001/* 002 * Copyright 2002-2016 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.util; 018 019import java.util.Collection; 020import java.util.Collections; 021 022/** 023 * A simple instance filter that checks if a given instance match based on 024 * a collection of includes and excludes element. 025 * 026 * <p>Subclasses may want to override {@link #match(Object, Object)} to provide 027 * a custom matching algorithm. 028 * 029 * @author Stephane Nicoll 030 * @since 4.1 031 */ 032public class InstanceFilter<T> { 033 034 private final Collection<? extends T> includes; 035 036 private final Collection<? extends T> excludes; 037 038 private final boolean matchIfEmpty; 039 040 041 /** 042 * Create a new instance based on includes/excludes collections. 043 * <p>A particular element will match if it "matches" the one of the element in the 044 * includes list and does not match one of the element in the excludes list. 045 * <p>Subclasses may redefine what matching means. By default, an element match with 046 * another if it is equals according to {@link Object#equals(Object)} 047 * <p>If both collections are empty, {@code matchIfEmpty} defines if 048 * an element matches or not. 049 * @param includes the collection of includes 050 * @param excludes the collection of excludes 051 * @param matchIfEmpty the matching result if both the includes and the excludes 052 * collections are empty 053 */ 054 public InstanceFilter(Collection<? extends T> includes, 055 Collection<? extends T> excludes, boolean matchIfEmpty) { 056 057 this.includes = (includes != null ? includes : Collections.<T>emptyList()); 058 this.excludes = (excludes != null ? excludes : Collections.<T>emptyList()); 059 this.matchIfEmpty = matchIfEmpty; 060 } 061 062 063 /** 064 * Determine if the specified {code instance} matches this filter. 065 */ 066 public boolean match(T instance) { 067 Assert.notNull(instance, "Instance to match must not be null"); 068 069 boolean includesSet = !this.includes.isEmpty(); 070 boolean excludesSet = !this.excludes.isEmpty(); 071 if (!includesSet && !excludesSet) { 072 return this.matchIfEmpty; 073 } 074 075 boolean matchIncludes = match(instance, this.includes); 076 boolean matchExcludes = match(instance, this.excludes); 077 if (!includesSet) { 078 return !matchExcludes; 079 } 080 if (!excludesSet) { 081 return matchIncludes; 082 } 083 return matchIncludes && !matchExcludes; 084 } 085 086 /** 087 * Determine if the specified {@code instance} is equal to the 088 * specified {@code candidate}. 089 * @param instance the instance to handle 090 * @param candidate a candidate defined by this filter 091 * @return {@code true} if the instance matches the candidate 092 */ 093 protected boolean match(T instance, T candidate) { 094 return instance.equals(candidate); 095 } 096 097 /** 098 * Determine if the specified {@code instance} matches one of the candidates. 099 * <p>If the candidates collection is {@code null}, returns {@code false}. 100 * @param instance the instance to check 101 * @param candidates a list of candidates 102 * @return {@code true} if the instance match or the candidates collection is null 103 */ 104 protected boolean match(T instance, Collection<? extends T> candidates) { 105 for (T candidate : candidates) { 106 if (match(instance, candidate)) { 107 return true; 108 } 109 } 110 return false; 111 } 112 113 @Override 114 public String toString() { 115 StringBuilder sb = new StringBuilder(getClass().getSimpleName()); 116 sb.append(": includes=").append(this.includes); 117 sb.append(", excludes=").append(this.excludes); 118 sb.append(", matchIfEmpty=").append(this.matchIfEmpty); 119 return sb.toString(); 120 } 121 122}