src/examples/plugins/pipeline/CompoundTransform.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */ 

import java.util.LinkedList;
import java.util.Iterator;

import org.apache.commons.digester.Digester;
import org.apache.commons.digester.plugins.PluginCreateRule;

/**
 * An implementation of the Transform interface which is configured with
 * a sequence of "subtransforms", and applies them one by one to the input
 * data.
 * <p>
 * This demonstrates that a plugged-in class can itself define plugin-points 
 * for user-defined classes if it wishes.
 */

public class CompoundTransform implements Transform {
    private LinkedList transforms = new LinkedList();
    
    public void addTransform(Transform transform) {
        transforms.add(transform);
    }
    
    public String transform(String s) {
        for(Iterator i = transforms.iterator(); i.hasNext(); ) {
            Transform t = (Transform) i.next();
            s = t.transform(s);
        }
        return s;
    }
    
    public static void addRules(Digester d, String patternPrefix) {
        PluginCreateRule pcr = new PluginCreateRule(Transform.class);
        d.addRule(patternPrefix+"/subtransform", pcr);
        d.addSetNext(patternPrefix+"/subtransform", "addTransform");
    }
}