freemarker.cache.MultiTemplateLoader Maven / Gradle / Ivy
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/*
* Copyright 2014 Attila Szegedi, Daniel Dekany, Jonathan Revusky
*
* 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 freemarker.cache;
import java.io.IOException;
import java.io.Reader;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
/**
* A {@link TemplateLoader} that uses a set of other loaders to load the templates.
* On every request, loaders are queried in the order of their appearance in the
* array of loaders provided to the constructor. However, if a request for some template
* name was already satisfied in the past by one of the loaders, that Loader is queried
* first (a soft affinity).
*
* This class is not thread-safe. If it's accessed from multiple
* threads concurrently, proper synchronization must be provided by the callers.
* Note that {@link TemplateCache}, the natural user of this class, provides the
* necessary synchronizations when it uses this class, so then you don't have to worry
* this.
*/
public class MultiTemplateLoader implements StatefulTemplateLoader
{
private final TemplateLoader[] loaders;
private final Map lastLoaderForName = Collections.synchronizedMap(new HashMap());
/**
* Creates a new multi template Loader that will use the specified loaders.
* @param loaders the loaders that are used to load templates.
*/
public MultiTemplateLoader(TemplateLoader[] loaders)
{
this.loaders = (TemplateLoader[])loaders.clone();
}
public Object findTemplateSource(String name)
throws
IOException
{
// Use soft affinity - give the loader that last found this
// resource a chance to find it again first.
TemplateLoader lastLoader = (TemplateLoader)lastLoaderForName.get(name);
if(lastLoader != null)
{
Object source = lastLoader.findTemplateSource(name);
if(source != null)
{
return new MultiSource(source, lastLoader);
}
}
// If there is no affine loader, or it could not find the resource
// again, try all loaders in order of appearance. If any manages
// to find the resource, then associate it as the new affine loader
// for this resource.
for(int i = 0; i < loaders.length; ++i)
{
TemplateLoader loader = loaders[i];
Object source = loader.findTemplateSource(name);
if(source != null)
{
lastLoaderForName.put(name, loader);
return new MultiSource(source, loader);
}
}
lastLoaderForName.remove(name);
// Resource not found
return null;
}
private Object modifyForIcI(Object source) {
// TODO Auto-generated method stub
return null;
}
public long getLastModified(Object templateSource)
{
return ((MultiSource)templateSource).getLastModified();
}
public Reader getReader(Object templateSource, String encoding)
throws
IOException
{
return ((MultiSource)templateSource).getReader(encoding);
}
public void closeTemplateSource(Object templateSource)
throws
IOException
{
((MultiSource)templateSource).close();
}
public void resetState()
{
lastLoaderForName.clear();
for (int i = 0; i < loaders.length; i++) {
TemplateLoader loader = loaders[i];
if(loader instanceof StatefulTemplateLoader) {
((StatefulTemplateLoader)loader).resetState();
}
}
}
/**
* Represents a template source bound to a specific template loader. It
* serves as the complete template source descriptor used by the
* MultiTemplateLoader class.
*/
static final class MultiSource
{
private final Object source;
private final TemplateLoader loader;
MultiSource(Object source, TemplateLoader loader)
{
this.source = source;
this.loader = loader;
}
long getLastModified()
{
return loader.getLastModified(source);
}
Reader getReader(String encoding)
throws
IOException
{
return loader.getReader(source, encoding);
}
void close()
throws
IOException
{
loader.closeTemplateSource(source);
}
Object getWrappedSource() {
return source;
}
public boolean equals(Object o) {
if(o instanceof MultiSource) {
MultiSource m = (MultiSource)o;
return m.loader.equals(loader) && m.source.equals(source);
}
return false;
}
public int hashCode() {
return loader.hashCode() + 31 * source.hashCode();
}
public String toString() {
return source.toString();
}
}
/**
* Show class name and some details that are useful in template-not-found errors.
*
* @since 2.3.21
*/
public String toString() {
StringBuffer sb = new StringBuffer();
sb.append("MultiTemplateLoader(");
for (int i = 0; i < loaders.length; i++) {
if (i != 0) {
sb.append(", ");
}
sb.append("loader").append(i + 1).append(" = ").append(loaders[i]);
}
sb.append(")");
return sb.toString();
}
}