/*
* Copyright (C) 2010 Google Inc.
*
* Licensed 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 com.google.clearsilver.jsilver.resourceloader;
import com.google.clearsilver.jsilver.exceptions.JSilverTemplateNotFoundException;
import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
import java.util.List;
/**
* ResourceLoader composed of other ResourceLoaders. When a resource is loaded, it will search
* through each ResourceLoader until it finds something.
*
* @see ResourceLoader
*/
public class CompositeResourceLoader implements ResourceLoader {
private final List<ResourceLoader> loaders = new ArrayList<ResourceLoader>();
public CompositeResourceLoader(Iterable<ResourceLoader> loaders) {
for (ResourceLoader loader : loaders) {
add(loader);
}
}
public CompositeResourceLoader(ResourceLoader... loaders) {
for (ResourceLoader loader : loaders) {
add(loader);
}
}
public void add(ResourceLoader loader) {
loaders.add(loader);
}
public Reader open(String name) throws IOException {
for (ResourceLoader loader : loaders) {
Reader reader = loader.open(name);
if (reader != null) {
return new ReaderTracer(reader, loader);
}
}
return null;
}
@Override
public Reader openOrFail(String name) throws JSilverTemplateNotFoundException, IOException {
Reader reader = open(name);
if (reader == null) {
throw new JSilverTemplateNotFoundException(name);
} else {
return reader;
}
}
public void close(Reader reader) throws IOException {
if (!(reader instanceof ReaderTracer)) {
throw new IllegalArgumentException("I can't close a reader I didn't open.");
}
reader.close();
}
/**
* We return the filename as the key of uniqueness as we assume that if this
* CompositeResourceLoader is in use, then there won't be another ResourceLoader that we are
* competing against. If we did need to worry about it we would want to prepend the key from
* above.
*/
@Override
public Object getKey(String filename) {
return filename;
}
/**
* Return the first non-null version identifier found among the ResourceLoaders, using the same
* search order as {@link #open(String)}.
*/
@Override
public Object getResourceVersionId(String filename) {
for (ResourceLoader loader : loaders) {
Object currentKey = loader.getResourceVersionId(filename);
if (currentKey != null) {
return currentKey;
}
}
return null;
}
/**
* Wraps a reader, associating it with the original ResourceLoader - this is necessary so when
* close() is called, we delegate back to original ResourceLoader.
*/
private static class ReaderTracer extends FilterReader {
private final ResourceLoader originalLoader;
public ReaderTracer(Reader in, ResourceLoader originalLoader) {
super(in);
this.originalLoader = originalLoader;
}
public void close() throws IOException {
originalLoader.close(in);
}
}
}