/*
* 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.
*/
/* $Id: CompositeImageLoader.java 924666 2010-03-18 08:26:30Z jeremias $ */
package org.apache.xmlgraphics.image.loader.impl;
import java.io.IOException;
import java.util.Map;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.xmlgraphics.image.loader.Image;
import org.apache.xmlgraphics.image.loader.ImageException;
import org.apache.xmlgraphics.image.loader.ImageFlavor;
import org.apache.xmlgraphics.image.loader.ImageInfo;
import org.apache.xmlgraphics.image.loader.ImageSessionContext;
import org.apache.xmlgraphics.image.loader.spi.ImageLoader;
/**
* Composite ImageLoader implementation in order to provide fallbacks when one ImageLoader
* fails due to some limitation.
*/
public class CompositeImageLoader extends AbstractImageLoader {
/** logger */
protected static Log log = LogFactory.getLog(CompositeImageLoader.class);
private ImageLoader[] loaders;
/**
* Main constructor.
* @param loaders the contained image loaders
*/
public CompositeImageLoader(ImageLoader[] loaders) {
if (loaders == null || loaders.length == 0) {
throw new IllegalArgumentException("Must at least pass one ImageLoader as parameter");
}
for (int i = 1, c = loaders.length; i < c; i++) {
if (!loaders[0].getTargetFlavor().equals(loaders[i].getTargetFlavor())) {
throw new IllegalArgumentException(
"All ImageLoaders must produce the same target flavor");
}
}
this.loaders = loaders;
}
/** {@inheritDoc} */
public ImageFlavor getTargetFlavor() {
return loaders[0].getTargetFlavor();
}
/** {@inheritDoc} */
public int getUsagePenalty() {
int maxPenalty = NO_LOADING_PENALTY;
for (int i = 1, c = loaders.length; i < c; i++) {
maxPenalty = Math.max(maxPenalty, loaders[i].getUsagePenalty());
}
return maxPenalty;
}
/** {@inheritDoc} */
public Image loadImage(ImageInfo info, Map hints, ImageSessionContext session)
throws ImageException, IOException {
ImageException firstException = null;
for (int i = 0, c = this.loaders.length; i < c; i++) {
ImageLoader loader = this.loaders[i];
try {
Image img = loader.loadImage(info, hints, session);
if (img != null && firstException != null) {
log.debug("First ImageLoader failed (" + firstException.getMessage()
+ "). Fallback was successful.");
}
return img;
} catch (ImageException ie) {
if (firstException == null) {
firstException = ie;
}
}
}
throw firstException;
}
/** {@inheritDoc} */
public String toString() {
StringBuffer sb = new StringBuffer("[");
for (int i = 0; i < this.loaders.length; i++) {
if (i > 0) {
sb.append(",");
}
sb.append(this.loaders[i].toString());
}
sb.append("]");
return sb.toString();
}
}