| 1 | /* |
| 2 | * Copyright 2006-2007 the original author or authors. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | package org.springframework.batch.classify; |
| 17 | |
| 18 | import java.io.Serializable; |
| 19 | import java.util.Comparator; |
| 20 | import java.util.HashMap; |
| 21 | import java.util.Map; |
| 22 | import java.util.Set; |
| 23 | import java.util.TreeSet; |
| 24 | import java.util.concurrent.ConcurrentHashMap; |
| 25 | import java.util.concurrent.ConcurrentMap; |
| 26 | |
| 27 | /** |
| 28 | * A {@link Classifier} for a parameterised object type based on a map. |
| 29 | * Classifies objects according to their inheritance relation with the supplied |
| 30 | * type map. If the object to be classified is one of the keys of the provided |
| 31 | * map, or is a subclass of one of the keys, then the map entry value for that |
| 32 | * key is returned. Otherwise returns the default value which is null by |
| 33 | * default. |
| 34 | * |
| 35 | * @author Dave Syer |
| 36 | * |
| 37 | */ |
| 38 | public class SubclassClassifier<T, C> implements Classifier<T, C> { |
| 39 | |
| 40 | private ConcurrentMap<Class<? extends T>, C> classified = new ConcurrentHashMap<Class<? extends T>, C>(); |
| 41 | |
| 42 | private C defaultValue = null; |
| 43 | |
| 44 | /** |
| 45 | * Create a {@link SubclassClassifier} with null default value. |
| 46 | * |
| 47 | */ |
| 48 | public SubclassClassifier() { |
| 49 | this(null); |
| 50 | } |
| 51 | |
| 52 | /** |
| 53 | * Create a {@link SubclassClassifier} with supplied default value. |
| 54 | * |
| 55 | * @param defaultValue |
| 56 | */ |
| 57 | public SubclassClassifier(C defaultValue) { |
| 58 | this(new HashMap<Class<? extends T>, C>(), defaultValue); |
| 59 | } |
| 60 | |
| 61 | /** |
| 62 | * Create a {@link SubclassClassifier} with supplied default value. |
| 63 | * |
| 64 | * @param defaultValue |
| 65 | */ |
| 66 | public SubclassClassifier(Map<Class<? extends T>, C> typeMap, C defaultValue) { |
| 67 | super(); |
| 68 | this.classified = new ConcurrentHashMap<Class<? extends T>, C>(typeMap); |
| 69 | this.defaultValue = defaultValue; |
| 70 | } |
| 71 | |
| 72 | /** |
| 73 | * Public setter for the default value for mapping keys that are not found |
| 74 | * in the map (or their subclasses). Defaults to false. |
| 75 | * |
| 76 | * @param defaultValue the default value to set |
| 77 | */ |
| 78 | public void setDefaultValue(C defaultValue) { |
| 79 | this.defaultValue = defaultValue; |
| 80 | } |
| 81 | |
| 82 | /** |
| 83 | * Set the classifications up as a map. The keys are types and these will be |
| 84 | * mapped along with all their subclasses to the corresponding value. The |
| 85 | * most specific types will match first. |
| 86 | * |
| 87 | * @param map a map from type to class |
| 88 | */ |
| 89 | public void setTypeMap(Map<Class<? extends T>, C> map) { |
| 90 | this.classified = new ConcurrentHashMap<Class<? extends T>, C>(map); |
| 91 | } |
| 92 | |
| 93 | /** |
| 94 | * Return the value from the type map whose key is the class of the given |
| 95 | * Throwable, or its nearest ancestor if a subclass. |
| 96 | * |
| 97 | */ |
| 98 | public C classify(T classifiable) { |
| 99 | |
| 100 | if (classifiable == null) { |
| 101 | return defaultValue; |
| 102 | } |
| 103 | |
| 104 | @SuppressWarnings("unchecked") |
| 105 | Class<? extends T> exceptionClass = (Class<? extends T>) classifiable.getClass(); |
| 106 | if (classified.containsKey(exceptionClass)) { |
| 107 | return classified.get(exceptionClass); |
| 108 | } |
| 109 | |
| 110 | // check for subclasses |
| 111 | Set<Class<? extends T>> classes = new TreeSet<Class<? extends T>>(new ClassComparator()); |
| 112 | classes.addAll(classified.keySet()); |
| 113 | for (Class<? extends T> cls : classes) { |
| 114 | if (cls.isAssignableFrom(exceptionClass)) { |
| 115 | C value = classified.get(cls); |
| 116 | this.classified.put(exceptionClass, value); |
| 117 | return value; |
| 118 | } |
| 119 | } |
| 120 | |
| 121 | return defaultValue; |
| 122 | } |
| 123 | |
| 124 | /** |
| 125 | * Return the default value supplied in the constructor (default false). |
| 126 | */ |
| 127 | final public C getDefault() { |
| 128 | return defaultValue; |
| 129 | } |
| 130 | |
| 131 | /** |
| 132 | * Comparator for classes to order by inheritance. |
| 133 | * |
| 134 | * @author Dave Syer |
| 135 | * |
| 136 | */ |
| 137 | private static class ClassComparator implements Comparator<Class<?>>, Serializable { |
| 138 | /** |
| 139 | * @return 1 if arg0 is assignable from arg1, -1 otherwise |
| 140 | * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object) |
| 141 | */ |
| 142 | public int compare(Class<?> arg0, Class<?> arg1) { |
| 143 | if (arg0.isAssignableFrom(arg1)) { |
| 144 | return 1; |
| 145 | } |
| 146 | return -1; |
| 147 | } |
| 148 | } |
| 149 | |
| 150 | } |