001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *
010 *        http://www.apache.org/licenses/LICENSE-2.0
011 *
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License.
018 */
019
020package org.apache.isis.core.commons.resource;
021
022import java.io.InputStream;
023import java.io.OutputStream;
024import java.util.ArrayList;
025import java.util.List;
026
027import org.slf4j.Logger;
028import org.slf4j.LoggerFactory;
029
030public class ResourceStreamSourceChainOfResponsibility extends ResourceStreamSourceAbstract {
031
032    private static Logger LOG = LoggerFactory.getLogger(ResourceStreamSourceChainOfResponsibility.class);
033
034    private final List<ResourceStreamSource> resourceStreamSources = new ArrayList<ResourceStreamSource>();
035
036    public ResourceStreamSourceChainOfResponsibility(final ResourceStreamSource... resourceStreamSources) {
037        for (final ResourceStreamSource rss : resourceStreamSources) {
038            addResourceStreamSource(rss);
039        }
040    }
041
042    public void addResourceStreamSource(final ResourceStreamSource rss) {
043        this.resourceStreamSources.add(rss);
044    }
045
046    @Override
047    protected InputStream doReadResource(final String resourcePath) {
048        for (final ResourceStreamSource rss : resourceStreamSources) {
049            final InputStream resourceStream = rss.readResource(resourcePath);
050            if (resourceStream != null) {
051                return resourceStream;
052            }
053        }
054        if (LOG.isDebugEnabled()) {
055            LOG.debug("could not load resource path '" + resourcePath + "' from " + getName());
056        }
057        return null;
058    }
059
060    @Override
061    public OutputStream writeResource(final String resourcePath) {
062        for (final ResourceStreamSource rss : resourceStreamSources) {
063            final OutputStream os = rss.writeResource(resourcePath);
064            if (os != null) {
065                return os;
066            }
067        }
068        return null;
069    }
070
071    @Override
072    public String getName() {
073        return "chain [" + resourceStreamNames() + "]";
074    }
075
076    private String resourceStreamNames() {
077        final StringBuilder buf = new StringBuilder();
078        boolean first = true;
079        for (final ResourceStreamSource rss : resourceStreamSources) {
080            if (first) {
081                first = false;
082            } else {
083                buf.append(", ");
084            }
085            buf.append(rss.getName());
086        }
087        return buf.toString();
088    }
089
090}