/*
* 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.ext.beans;
import java.util.Enumeration;
import java.util.NoSuchElementException;
import freemarker.template.TemplateCollectionModel;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelException;
import freemarker.template.TemplateModelIterator;
/**
* <p>A class that adds {@link TemplateModelIterator} functionality to the
* {@link Enumeration} interface implementers.
* </p> <p>Using the model as a collection model is NOT thread-safe, as
* enumerations are inherently not thread-safe.
* Further, you can iterate over it only once. Attempts to call the
* {@link #iterator()} method after it was already driven to the end once will
* throw an exception.</p>
*/
public class EnumerationModel
extends
BeanModel
implements
TemplateModelIterator,
TemplateCollectionModel {
private boolean accessed = false;
/**
* Creates a new model that wraps the specified enumeration object.
* @param enumeration the enumeration object to wrap into a model.
* @param wrapper the {@link BeansWrapper} associated with this model.
* Every model has to have an associated {@link BeansWrapper} instance. The
* model gains many attributes from its wrapper, including the caching
* behavior, method exposure level, method-over-item shadowing policy etc.
*/
public EnumerationModel(Enumeration enumeration, BeansWrapper wrapper) {
super(enumeration, wrapper);
}
/**
* This allows the enumeration to be used in a <tt><#list></tt> block.
* @return "this"
*/
public TemplateModelIterator iterator() throws TemplateModelException {
synchronized (this) {
if (accessed) {
throw new TemplateModelException(
"This collection is stateful and can not be iterated over the" +
" second time.");
}
accessed = true;
}
return this;
}
/**
* Calls underlying {@link Enumeration#nextElement()}.
*/
public boolean hasNext() {
return ((Enumeration) object).hasMoreElements();
}
/**
* Calls underlying {@link Enumeration#nextElement()} and wraps the result.
*/
public TemplateModel next()
throws TemplateModelException {
try {
return wrap(((Enumeration) object).nextElement());
} catch (NoSuchElementException e) {
throw new TemplateModelException(
"No more elements in the enumeration.");
}
}
/**
* Returns {@link Enumeration#hasMoreElements()}. Therefore, an
* enumeration that has no more element evaluates to false, and an
* enumeration that has further elements evaluates to true.
*/
public boolean getAsBoolean() {
return hasNext();
}
}