/*
* Copyright 2002-2007 the original author or authors.
*
* 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 org.springmodules.template.engine.velocity.extended;
import java.io.IOException;
import java.io.Writer;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.context.Context;
import org.apache.velocity.context.InternalContextAdapterImpl;
import org.apache.velocity.runtime.parser.node.SimpleNode;
/**
* A special template that initializes and holds a compiled runtime representation of a velocity template (in the
* form of a {@link SimpleNode}. This template can be retrieved from the {@link ExtendedVelocityEngine} by calling
* {@link ExtendedVelocityEngine#getSpecialTemplate(org.springframework.core.io.Resource, String)} or
* {@link ExtendedVelocityEngine#getSpecialTemplate(org.springframework.core.io.Resource, String)}. This template
* was specially introduced as currently with the original velocity template engine, there is no way to create
* a compiled runtime representation of a template directly out of an input stream or a reader.
*
* @author Uri Boness
* @see ExtendedVelocityEngine#getSpecialTemplate(org.springframework.core.io.Resource, String)
* @see ExtendedVelocityEngine#getSpecialTemplate(java.io.Reader, String, String)
* @see ExtendedRuntimeInstance#getSpecialTemplate(java.io.Reader, String, String)
*/
public class SpecialTemplate {
private final static Log logger = LogFactory.getLog(SpecialTemplate.class);
private final SimpleNode node;
private final String name;
/**
* Constructs a new SpecialTemplate with given node (represents the compiled template), runtime instance, and a name
* that will be used for log messages.
*
* @param node The compile runtime representation of the template.
* @param ri The velocity runtime instance to be used.
* @param name A template name that will be used in log messages.
*/
public SpecialTemplate(SimpleNode node, ExtendedRuntimeInstance ri, String name) {
this.node = node;
this.name = name;
init(node, ri, name);
}
/**
* Merges this template with the given velocity context and writes the merge result to the given writer.
*
* @param context The context to be merged with this template.
* @param writer The writer to which the merged template will be written.
* @throws IOException thrown when the merging fails.
*/
public void merge(Context context, Writer writer) throws IOException {
InternalContextAdapterImpl ica = new InternalContextAdapterImpl(context);
ica.pushCurrentTemplateName(name);
try {
node.render(ica, writer);
} catch (IOException ioe) {
logger.error("Could not merge veloctiy template '" + name + "'", ioe);
throw ioe;
} finally {
ica.popCurrentTemplateName();
}
}
//============================================== Helper Methods ====================================================
/**
* Initializes this the given node using the given velocity runtime.
*
* @param node The node to initialize.
* @param ri The velcotiy runtime instance that will be used while initilizing.
* @param name A name to be associated with the template to be used in log messages.
*/
protected static void init(SimpleNode node, ExtendedRuntimeInstance ri, String name) {
InternalContextAdapterImpl ica = new InternalContextAdapterImpl( new VelocityContext() );
try {
ica.pushCurrentTemplateName( name );
node.init(ica, ri);
} finally {
ica.popCurrentTemplateName();
}
}
}