freemarker.ext.beans.IteratorModel Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.Iterator;
import java.util.NoSuchElementException;
import freemarker.template.TemplateCollectionModel;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelException;
import freemarker.template.TemplateModelIterator;
/**
* A class that adds {@link TemplateModelIterator} functionality to the
* {@link Iterator} interface implementers.
*
* It differs from the {@link freemarker.template.SimpleCollection} in that
* it inherits from {@link BeanModel}, and therefore you can call methods on
* it directly, even to the effect of calling iterator.remove() in
* the template.
Using the model as a collection model is NOT
* thread-safe, as iterators 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.
*/
public class IteratorModel
extends
BeanModel
implements
TemplateModelIterator,
TemplateCollectionModel {
private boolean accessed = false;
/**
* Creates a new model that wraps the specified iterator object.
* @param iterator the iterator 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 IteratorModel(Iterator iterator, BeansWrapper wrapper) {
super(iterator, wrapper);
}
/**
* This allows the iterator to be used in a <#list> 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 Iterator#hasNext()}.
*/
public boolean hasNext() {
return ((Iterator) object).hasNext();
}
/**
* Calls underlying {@link Iterator#next()} and wraps the result.
*/
public TemplateModel next()
throws TemplateModelException {
try {
return wrap(((Iterator) object).next());
} catch (NoSuchElementException e) {
throw new TemplateModelException(
"No more elements in the iterator.", e);
}
}
/**
* Returns {@link Iterator#hasNext()}. Therefore, an
* iterator that has no more element evaluates to false, and an
* iterator that has further elements evaluates to true.
*/
public boolean getAsBoolean() {
return hasNext();
}
}