/*
* Copyright 2001-2004 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.Collection;
import java.util.Iterator;
import org.apache.commons.collections.Transformer;
/**
* Transformer implementation that chains the specified transformers together.
* <p>
* The input object is passed to the first transformer. The transformed result
* is passed to the second transformer and so on.
*
* @since Commons Collections 3.0
* @version $Revision: 348444 $ $Date: 2005-11-23 14:06:56 +0000 (Wed, 23 Nov 2005) $
*
* @author Stephen Colebourne
*/
public class ChainedTransformer implements Transformer, Serializable {
/** Serial version UID */
private static final long serialVersionUID = 3514945074733160196L;
/** The transformers to call in turn */
private final Transformer[] iTransformers;
/**
* Factory method that performs validation and copies the parameter array.
*
* @param transformers the transformers to chain, copied, no nulls
* @return the <code>chained</code> transformer
* @throws IllegalArgumentException if the transformers array is null
* @throws IllegalArgumentException if any transformer in the array is null
*/
public static Transformer getInstance(Transformer[] transformers) {
FunctorUtils.validate(transformers);
if (transformers.length == 0) {
return NOPTransformer.INSTANCE;
}
transformers = FunctorUtils.copy(transformers);
return new ChainedTransformer(transformers);
}
/**
* Create a new Transformer that calls each transformer in turn, passing the
* result into the next transformer. The ordering is that of the iterator()
* method on the collection.
*
* @param transformers a collection of transformers to chain
* @return the <code>chained</code> transformer
* @throws IllegalArgumentException if the transformers collection is null
* @throws IllegalArgumentException if any transformer in the collection is null
*/
public static Transformer getInstance(Collection transformers) {
if (transformers == null) {
throw new IllegalArgumentException("Transformer collection must not be null");
}
if (transformers.size() == 0) {
return NOPTransformer.INSTANCE;
}
// convert to array like this to guarantee iterator() ordering
Transformer[] cmds = new Transformer[transformers.size()];
int i = 0;
for (Iterator it = transformers.iterator(); it.hasNext();) {
cmds[i++] = (Transformer) it.next();
}
FunctorUtils.validate(cmds);
return new ChainedTransformer(cmds);
}
/**
* Factory method that performs validation.
*
* @param transformer1 the first transformer, not null
* @param transformer2 the second transformer, not null
* @return the <code>chained</code> transformer
* @throws IllegalArgumentException if either transformer is null
*/
public static Transformer getInstance(Transformer transformer1, Transformer transformer2) {
if (transformer1 == null || transformer2 == null) {
throw new IllegalArgumentException("Transformers must not be null");
}
Transformer[] transformers = new Transformer[] { transformer1, transformer2 };
return new ChainedTransformer(transformers);
}
/**
* Constructor that performs no validation.
* Use <code>getInstance</code> if you want that.
*
* @param transformers the transformers to chain, not copied, no nulls
*/
public ChainedTransformer(Transformer[] transformers) {
super();
iTransformers = transformers;
}
/**
* Transforms the input to result via each decorated transformer
*
* @param object the input object passed to the first transformer
* @return the transformed result
*/
public Object transform(Object object) {
for (int i = 0; i < iTransformers.length; i++) {
object = iTransformers[i].transform(object);
}
return object;
}
/**
* Gets the transformers, do not modify the array.
* @return the transformers
* @since Commons Collections 3.1
*/
public Transformer[] getTransformers() {
return iTransformers;
}
}