001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.discovery.resource.classes;
018
019import org.apache.commons.discovery.ResourceClass;
020import org.apache.commons.discovery.ResourceClassDiscover;
021import org.apache.commons.discovery.ResourceClassIterator;
022import org.apache.commons.discovery.ResourceIterator;
023import org.apache.commons.discovery.ResourceNameIterator;
024import org.apache.commons.discovery.resource.ClassLoaders;
025import org.apache.commons.discovery.resource.ResourceDiscoverImpl;
026
027/**
028 * Default {@link ResourceClassDiscover} implementation.
029 *
030 * @param <T> The SPI type
031 */
032public abstract class ResourceClassDiscoverImpl<T> extends ResourceDiscoverImpl implements ResourceClassDiscover<T> {
033
034    /**
035     * Construct a new resource discoverer.
036     */
037    public ResourceClassDiscoverImpl() {
038        super();
039    }
040
041    /**
042     * Construct a new resource discoverer.
043     *
044     * @param classLoaders The class loaders holder
045     */
046    public ResourceClassDiscoverImpl(ClassLoaders classLoaders) {
047        super(classLoaders);
048    }
049
050    /**
051     * {@inheritDoc}
052     */
053    @Override
054    public ResourceNameIterator findResourceNames(String resourceName) {
055        return findResourceClasses(resourceName);
056    }
057
058    /**
059     * {@inheritDoc}
060     */
061    @Override
062    public ResourceNameIterator findResourceNames(ResourceNameIterator resourceNames) {
063        return findResourceClasses(resourceNames);
064    }
065
066    /**
067     * {@inheritDoc}
068     */
069    @Override
070    public ResourceIterator findResources(String resourceName) {
071        return findResourceClasses(resourceName);
072    }
073
074    /**
075     * {@inheritDoc}
076     */
077    @Override
078    public ResourceIterator findResources(ResourceNameIterator resourceNames) {
079        return findResourceClasses(resourceNames);
080    }
081
082    /**
083     * Locate class resources that are bound to <code>className</code>.
084     *
085     * @param className The class name has to be located
086     * @return The located resources iterator
087     */
088    public abstract ResourceClassIterator<T> findResourceClasses(String className);
089
090    /**
091     * Locate class resources that are bound to {@code resourceNames}.
092     *
093     * @param inputNames The resource name iterator
094     * @return a new {@link ResourceClassIterator} over the given resource name iterator
095     */
096    public ResourceClassIterator<T> findResourceClasses(final ResourceNameIterator inputNames) {
097        return new ResourceClassIterator<T>() {
098            private ResourceClassIterator<T> classes = null;
099            private ResourceClass<T> resource = null;
100
101            public boolean hasNext() {
102                if (resource == null) {
103                    resource = getNextResource();
104                }
105                return resource != null;
106            }
107
108            @Override
109            public ResourceClass<T> nextResourceClass() {
110                ResourceClass<T> rsrc = resource;
111                resource = null;
112                return rsrc;
113            }
114
115            private ResourceClass<T> getNextResource() {
116                while (inputNames.hasNext() &&
117                       (classes == null  ||  !classes.hasNext())) {
118                    classes =
119                        findResourceClasses(inputNames.nextResourceName());
120                }
121
122                return (classes != null  &&  classes.hasNext())
123                       ? classes.nextResourceClass()
124                       : null;
125            }
126        };
127    }
128
129}