001/* 002 * Copyright 2002-2018 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 022import org.springframework.lang.Nullable; 023 024/** 025 * A simple instance filter that checks if a given instance match based on 026 * a collection of includes and excludes element. 027 * 028 * <p>Subclasses may want to override {@link #match(Object, Object)} to provide 029 * a custom matching algorithm. 030 * 031 * @author Stephane Nicoll 032 * @since 4.1 033 * @param <T> the instance type 034 */ 035public class InstanceFilter<T> { 036 037 private final Collection<? extends T> includes; 038 039 private final Collection<? extends T> excludes; 040 041 private final boolean matchIfEmpty; 042 043 044 /** 045 * Create a new instance based on includes/excludes collections. 046 * <p>A particular element will match if it "matches" the one of the element in the 047 * includes list and does not match one of the element in the excludes list. 048 * <p>Subclasses may redefine what matching means. By default, an element match with 049 * another if it is equals according to {@link Object#equals(Object)} 050 * <p>If both collections are empty, {@code matchIfEmpty} defines if 051 * an element matches or not. 052 * @param includes the collection of includes 053 * @param excludes the collection of excludes 054 * @param matchIfEmpty the matching result if both the includes and the excludes 055 * collections are empty 056 */ 057 public InstanceFilter(@Nullable Collection<? extends T> includes, 058 @Nullable Collection<? extends T> excludes, boolean matchIfEmpty) { 059 060 this.includes = (includes != null ? includes : Collections.emptyList()); 061 this.excludes = (excludes != null ? excludes : Collections.emptyList()); 062 this.matchIfEmpty = matchIfEmpty; 063 } 064 065 066 /** 067 * Determine if the specified {code instance} matches this filter. 068 */ 069 public boolean match(T instance) { 070 Assert.notNull(instance, "Instance to match must not be null"); 071 072 boolean includesSet = !this.includes.isEmpty(); 073 boolean excludesSet = !this.excludes.isEmpty(); 074 if (!includesSet && !excludesSet) { 075 return this.matchIfEmpty; 076 } 077 078 boolean matchIncludes = match(instance, this.includes); 079 boolean matchExcludes = match(instance, this.excludes); 080 if (!includesSet) { 081 return !matchExcludes; 082 } 083 if (!excludesSet) { 084 return matchIncludes; 085 } 086 return matchIncludes && !matchExcludes; 087 } 088 089 /** 090 * Determine if the specified {@code instance} is equal to the 091 * specified {@code candidate}. 092 * @param instance the instance to handle 093 * @param candidate a candidate defined by this filter 094 * @return {@code true} if the instance matches the candidate 095 */ 096 protected boolean match(T instance, T candidate) { 097 return instance.equals(candidate); 098 } 099 100 /** 101 * Determine if the specified {@code instance} matches one of the candidates. 102 * <p>If the candidates collection is {@code null}, returns {@code false}. 103 * @param instance the instance to check 104 * @param candidates a list of candidates 105 * @return {@code true} if the instance match or the candidates collection is null 106 */ 107 protected boolean match(T instance, Collection<? extends T> candidates) { 108 for (T candidate : candidates) { 109 if (match(instance, candidate)) { 110 return true; 111 } 112 } 113 return false; 114 } 115 116 @Override 117 public String toString() { 118 StringBuilder sb = new StringBuilder(getClass().getSimpleName()); 119 sb.append(": includes=").append(this.includes); 120 sb.append(", excludes=").append(this.excludes); 121 sb.append(", matchIfEmpty=").append(this.matchIfEmpty); 122 return sb.toString(); 123 } 124 125}