| /* |
| * Copyright 2001-2004,2006 The Apache Software Foundation |
| * |
| * 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 |
| * |
| * http://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.apache.commons.collections.functors; |
| |
| import java.io.Serializable; |
| import java.util.Iterator; |
| import java.util.Map; |
| |
| import org.apache.commons.collections.Predicate; |
| import org.apache.commons.collections.Transformer; |
| |
| /** |
| * Transformer implementation calls the transformer whose predicate returns true, |
| * like a switch statement. |
| * |
| * @since Commons Collections 3.0 |
| * @version $Revision: 1.1 $ $Date: 2009/05/27 22:16:32 $ |
| * |
| * @author Stephen Colebourne |
| */ |
| public class SwitchTransformer implements Transformer, Serializable { |
| |
| /** Serial version UID */ |
| private static final long serialVersionUID = -6404460890903469332L; |
| |
| /** The tests to consider */ |
| private final Predicate[] iPredicates; |
| /** The matching transformers to call */ |
| private final Transformer[] iTransformers; |
| /** The default transformer to call if no tests match */ |
| private final Transformer iDefault; |
| |
| /** |
| * Factory method that performs validation and copies the parameter arrays. |
| * |
| * @param predicates array of predicates, cloned, no nulls |
| * @param transformers matching array of transformers, cloned, no nulls |
| * @param defaultTransformer the transformer to use if no match, null means return null |
| * @return the <code>chained</code> transformer |
| * @throws IllegalArgumentException if array is null |
| * @throws IllegalArgumentException if any element in the array is null |
| */ |
| public static Transformer getInstance(Predicate[] predicates, Transformer[] transformers, Transformer defaultTransformer) { |
| FunctorUtils.validate(predicates); |
| FunctorUtils.validate(transformers); |
| if (predicates.length != transformers.length) { |
| throw new IllegalArgumentException("The predicate and transformer arrays must be the same size"); |
| } |
| if (predicates.length == 0) { |
| return (defaultTransformer == null ? ConstantTransformer.NULL_INSTANCE : defaultTransformer); |
| } |
| predicates = FunctorUtils.copy(predicates); |
| transformers = FunctorUtils.copy(transformers); |
| return new SwitchTransformer(predicates, transformers, defaultTransformer); |
| } |
| |
| /** |
| * Create a new Transformer that calls one of the transformers depending |
| * on the predicates. |
| * <p> |
| * The Map consists of Predicate keys and Transformer values. A transformer |
| * is called if its matching predicate returns true. Each predicate is evaluated |
| * until one returns true. If no predicates evaluate to true, the default |
| * transformer is called. The default transformer is set in the map with a |
| * null key. The ordering is that of the iterator() method on the entryset |
| * collection of the map. |
| * |
| * @param predicatesAndTransformers a map of predicates to transformers |
| * @return the <code>switch</code> transformer |
| * @throws IllegalArgumentException if the map is null |
| * @throws IllegalArgumentException if any transformer in the map is null |
| * @throws ClassCastException if the map elements are of the wrong type |
| */ |
| public static Transformer getInstance(Map predicatesAndTransformers) { |
| Transformer[] transformers = null; |
| Predicate[] preds = null; |
| if (predicatesAndTransformers == null) { |
| throw new IllegalArgumentException("The predicate and transformer map must not be null"); |
| } |
| if (predicatesAndTransformers.size() == 0) { |
| return ConstantTransformer.NULL_INSTANCE; |
| } |
| // convert to array like this to guarantee iterator() ordering |
| Transformer defaultTransformer = (Transformer) predicatesAndTransformers.remove(null); |
| int size = predicatesAndTransformers.size(); |
| if (size == 0) { |
| return (defaultTransformer == null ? ConstantTransformer.NULL_INSTANCE : defaultTransformer); |
| } |
| transformers = new Transformer[size]; |
| preds = new Predicate[size]; |
| int i = 0; |
| for (Iterator it = predicatesAndTransformers.entrySet().iterator(); it.hasNext();) { |
| Map.Entry entry = (Map.Entry) it.next(); |
| preds[i] = (Predicate) entry.getKey(); |
| transformers[i] = (Transformer) entry.getValue(); |
| i++; |
| } |
| return new SwitchTransformer(preds, transformers, defaultTransformer); |
| } |
| |
| /** |
| * Constructor that performs no validation. |
| * Use <code>getInstance</code> if you want that. |
| * |
| * @param predicates array of predicates, not cloned, no nulls |
| * @param transformers matching array of transformers, not cloned, no nulls |
| * @param defaultTransformer the transformer to use if no match, null means return null |
| */ |
| public SwitchTransformer(Predicate[] predicates, Transformer[] transformers, Transformer defaultTransformer) { |
| super(); |
| iPredicates = predicates; |
| iTransformers = transformers; |
| iDefault = (defaultTransformer == null ? ConstantTransformer.NULL_INSTANCE : defaultTransformer); |
| } |
| |
| /** |
| * Transforms the input to result by calling the transformer whose matching |
| * predicate returns true. |
| * |
| * @param input the input object to transform |
| * @return the transformed result |
| */ |
| public Object transform(Object input) { |
| for (int i = 0; i < iPredicates.length; i++) { |
| if (iPredicates[i].evaluate(input) == true) { |
| return iTransformers[i].transform(input); |
| } |
| } |
| return iDefault.transform(input); |
| } |
| |
| /** |
| * Gets the predicates, do not modify the array. |
| * |
| * @return the predicates |
| * @since Commons Collections 3.1 |
| */ |
| public Predicate[] getPredicates() { |
| return iPredicates; |
| } |
| |
| /** |
| * Gets the transformers, do not modify the array. |
| * |
| * @return the transformers |
| * @since Commons Collections 3.1 |
| */ |
| public Transformer[] getTransformers() { |
| return iTransformers; |
| } |
| |
| /** |
| * Gets the default transformer. |
| * |
| * @return the default transformer |
| * @since Commons Collections 3.1 |
| */ |
| public Transformer getDefaultTransformer() { |
| return iDefault; |
| } |
| |
| } |