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/*
 * 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.template;

import java.io.Serializable;
import java.util.Iterator;

import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
import freemarker.ext.util.WrapperTemplateModel;
import freemarker.template.utility.ObjectWrapperWithAPISupport;

/**
 * Adapts an {@link Iterator} to the corresponding {@link TemplateModel} interface(s), most importantly to
 * {@link TemplateCollectionModel}. The resulting {@link TemplateCollectionModel} can only be listed (iterated) once.
 * If the user tries list the variable for a second time, an exception will be thrown instead of silently gettig an
 * empty (or partial) listing.
 * 
 * 

* Thread safety: A {@link DefaultListAdapter} is as thread-safe as the array that it wraps is. Normally you only * have to consider read-only access, as the FreeMarker template language doesn't allow writing these sequences (though * of course, Java methods called from the template can violate this rule). * *

* This adapter is used by {@link DefaultObjectWrapper} if its {@code useAdaptersForCollections} property is * {@code true}, which is the default when its {@code incompatibleImprovements} property is 2.3.22 or higher. * * @since 2.3.22 */ public class DefaultIteratorAdapter extends WrappingTemplateModel implements TemplateCollectionModel, AdapterTemplateModel, WrapperTemplateModel, TemplateModelWithAPISupport, Serializable { @SuppressFBWarnings(value="SE_BAD_FIELD", justification="We hope it's Seralizable") private final Iterator iterator; private boolean iteratorOwnedBySomeone; /** * Factory method for creating new adapter instances. * * @param iterator * The iterator to adapt; can't be {@code null}. */ public static DefaultIteratorAdapter adapt(Iterator iterator, ObjectWrapper wrapper) { return new DefaultIteratorAdapter(iterator, wrapper); } private DefaultIteratorAdapter(Iterator iterator, ObjectWrapper wrapper) { super(wrapper); this.iterator = iterator; } @Override public Object getWrappedObject() { return iterator; } @Override public Object getAdaptedObject(Class hint) { return getWrappedObject(); } @Override public TemplateModelIterator iterator() throws TemplateModelException { return new SimpleTemplateModelIterator(); } @Override public TemplateModel getAPI() throws TemplateModelException { return ((ObjectWrapperWithAPISupport) getObjectWrapper()).wrapAsAPI(iterator); } /** * Not thread-safe. */ private class SimpleTemplateModelIterator implements TemplateModelIterator { private boolean iteratorOwnedByMe; @Override public TemplateModel next() throws TemplateModelException { if (!iteratorOwnedByMe) { checkNotOwner(); iteratorOwnedBySomeone = true; iteratorOwnedByMe = true; } if (!iterator.hasNext()) { throw new TemplateModelException("The collection has no more items."); } Object value = iterator.next(); return value instanceof TemplateModel ? (TemplateModel) value : wrap(value); } @Override public boolean hasNext() throws TemplateModelException { // Calling hasNext may looks safe, but I have met sync. problems. if (!iteratorOwnedByMe) { checkNotOwner(); } return iterator.hasNext(); } private void checkNotOwner() throws TemplateModelException { if (iteratorOwnedBySomeone) { throw new TemplateModelException( "This collection value wraps a java.util.Iterator, thus it can be listed only once."); } } } }





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