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SubclassClassifier.java
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SubclassClassifier.java
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/*
* Copyright 2006-2013 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.classify;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
/**
* A {@link Classifier} for a parameterised object type based on a map. Classifies objects
* according to their inheritance relation with the supplied type map. If the object to be
* classified is one of the keys of the provided map, or is a subclass of one of the keys,
* then the map entry value for that key is returned. Otherwise returns the default value
* which is null by default.
*
* @author Dave Syer
* @author Gary Russell
* @param <T> the type of the thing to classify
* @param <C> the output of the classifier
*/
@SuppressWarnings("serial")
public class SubclassClassifier<T, C> implements Classifier<T, C> {
private ConcurrentMap<Class<? extends T>, C> classified = new ConcurrentHashMap<Class<? extends T>, C>();
private C defaultValue = null;
/**
* Create a {@link SubclassClassifier} with null default value.
*
*/
public SubclassClassifier() {
this(null);
}
/**
* Create a {@link SubclassClassifier} with supplied default value.
* @param defaultValue the default value
*/
public SubclassClassifier(C defaultValue) {
this(new HashMap<Class<? extends T>, C>(), defaultValue);
}
/**
* Create a {@link SubclassClassifier} with supplied default value.
* @param defaultValue the default value
* @param typeMap the map of types
*/
public SubclassClassifier(Map<Class<? extends T>, C> typeMap, C defaultValue) {
super();
this.classified = new ConcurrentHashMap<Class<? extends T>, C>(typeMap);
this.defaultValue = defaultValue;
}
/**
* Public setter for the default value for mapping keys that are not found in the map
* (or their subclasses). Defaults to false.
* @param defaultValue the default value to set
*/
public void setDefaultValue(C defaultValue) {
this.defaultValue = defaultValue;
}
/**
* Set the classifications up as a map. The keys are types and these will be mapped
* along with all their subclasses to the corresponding value. The most specific types
* will match first.
* @param map a map from type to class
*/
public void setTypeMap(Map<Class<? extends T>, C> map) {
this.classified = new ConcurrentHashMap<Class<? extends T>, C>(map);
}
/**
* The keys is the type and this will be mapped along with all subclasses to the
* corresponding value. The most specific types will match first.
* @param type the type of the input object
* @param target the target value for all such types
*/
public void add(Class<? extends T> type, C target) {
this.classified.put(type, target);
}
/**
* Return the value from the type map whose key is the class of the given Throwable,
* or its nearest ancestor if a subclass.
* @return C the classified value
* @param classifiable the classifiable thing
*/
@Override
public C classify(T classifiable) {
if (classifiable == null) {
return this.defaultValue;
}
@SuppressWarnings("unchecked")
Class<? extends T> exceptionClass = (Class<? extends T>) classifiable.getClass();
if (this.classified.containsKey(exceptionClass)) {
return this.classified.get(exceptionClass);
}
// check for subclasses
C value = null;
for (Class<?> cls = exceptionClass; !cls.equals(Object.class) && value == null; cls = cls.getSuperclass()) {
value = this.classified.get(cls);
}
// check for interfaces subclasses
if (value == null) {
for (Class<?> cls = exceptionClass; !cls.equals(Object.class) && value == null; cls = cls.getSuperclass()) {
for (Class<?> ifc : cls.getInterfaces()) {
value = this.classified.get(ifc);
if (value != null) {
break;
}
}
}
}
// ConcurrentHashMap doesn't allow nulls
if (value != null) {
this.classified.put(exceptionClass, value);
}
if (value == null) {
value = this.defaultValue;
}
return value;
}
/**
* Return the default value supplied in the constructor (default false).
* @return C the default value
*/
final public C getDefault() {
return this.defaultValue;
}
protected Map<Class<? extends T>, C> getClassified() {
return this.classified;
}
}