org.apache.commons.discovery.resource.names.NameDiscoverers.java Source code

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Here is the source code for org.apache.commons.discovery.resource.names.NameDiscoverers.java

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/*
 * 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.
 */
package org.apache.commons.discovery.resource.names;

import java.util.Vector;

import org.apache.commons.discovery.ResourceNameDiscover;
import org.apache.commons.discovery.ResourceNameIterator;
import org.apache.commons.discovery.log.DiscoveryLogFactory;
import org.apache.commons.logging.Log;

/**
 * Holder for multiple ResourceNameDiscover instances.
 * The result is the union of the results from each
 * (not a chained sequence, where results feed the next in line.
 *
 * @author Richard A. Sitze
 */
public class NameDiscoverers extends ResourceNameDiscoverImpl implements ResourceNameDiscover {
    private static Log log = DiscoveryLogFactory.newLog(NameDiscoverers.class);

    public static void setLog(Log _log) {
        log = _log;
    }

    private Vector discoverers = new Vector();

    /**
     *  Construct a new resource name discoverer
     */
    public NameDiscoverers() {
    }

    /**
     * Specify an additional class loader to be used in searching.
     * The order of loaders determines the order of the result.
     * It is recommended to add the most specific loaders first.
     */
    public void addResourceNameDiscover(ResourceNameDiscover discover) {
        if (discover != null) {
            discoverers.addElement(discover);
        }
    }

    protected ResourceNameDiscover getResourceNameDiscover(int idx) {
        return (ResourceNameDiscover) discoverers.get(idx);
    }

    protected int size() {
        return discoverers.size();
    }

    /**
     * Set of results of all discoverers.
     * 
     * @return ResourceIterator
     */
    public ResourceNameIterator findResourceNames(final String resourceName) {
        if (log.isDebugEnabled())
            log.debug("find: resourceName='" + resourceName + "'");

        return new ResourceNameIterator() {
            private int idx = 0;
            private ResourceNameIterator iterator = null;

            public boolean hasNext() {
                if (iterator == null || !iterator.hasNext()) {
                    iterator = getNextIterator();
                    if (iterator == null) {
                        return false;
                    }
                }
                return iterator.hasNext();
            }

            public String nextResourceName() {
                return iterator.nextResourceName();
            }

            private ResourceNameIterator getNextIterator() {
                while (idx < size()) {
                    ResourceNameIterator iter = getResourceNameDiscover(idx++).findResourceNames(resourceName);

                    if (iter.hasNext()) {
                        return iter;
                    }
                }
                return null;
            }
        };
    }
}