freemarker.cache.MultiTemplateLoader Maven / Gradle / Ivy
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Google App Engine compliant variation of FreeMarker.
FreeMarker is a "template engine"; a generic tool to generate text output based on templates.
/*
* Copyright (c) 2003 The Visigoth Software Society. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowledgement:
* "This product includes software developed by the
* Visigoth Software Society (http://www.visigoths.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
*
* 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the
* project contributors may be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [email protected].
*
* 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
* nor may "FreeMarker" or "Visigoth" appear in their names
* without prior written permission of the Visigoth Software Society.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE VISIGOTH SOFTWARE SOCIETY OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Visigoth Software Society. For more
* information on the Visigoth Software Society, please see
* http://www.visigoths.org/
*/
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 that this Loader owns. 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 is 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 the class.
* @author Attila Szegedi, szegedia at freemail dot hu
* @version $Id: MultiTemplateLoader.java,v 1.12.2.2 2007/04/04 07:51:16 szegedia Exp $
*/
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;
}
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.
*/
private 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);
}
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();
}
}
}