/**
* Licensed to jclouds, Inc. (jclouds) under one or more
* contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. jclouds 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 org.jclouds.collect;
import java.util.Iterator;
import com.google.common.annotations.Beta;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.Iterators;
import com.google.common.collect.UnmodifiableIterator;
/**
* Extends {@link FluentIterable} allowing you to lazily advance through
* sequence of pages in a result set. Typically used in APIs that return only a
* certain number of records at a time.
* </p>
* Simplest usage is to employ the {@link #concat} convenience function, and iterate.
* </p>
* <pre>
* FluentIterable<? extends Image> images = imageApi.listInDetail().concat();
*
* for (Image image: images) {
* System.out.println(image);
* }
* </pre>
* </p>
* Another usage is to employ the {@link #concat} convenience function, and one
* of the methods from {@link FluentIterable}.
* </p>
* <pre>
* Optional<? extends Image> image = imageApi.listInDetail().concat().firstMatch(isInterestingImage());
* System.out.println(image.orNull());
* ...
* private static Predicate<Image> isInterestingImage() {
* return new Predicate<Image>() {
* {@literal @}Override
* public boolean apply(Image image) {
* return image.getName().startsWith("Arch");
* }
* };
* }
* </pre>
*
* @author Adrian Cole
*/
@Beta
public abstract class PagedIterable<E> extends FluentIterable<IterableWithMarker<E>> {
/**
* Combines all the pages into a single unmodifiable iterable. ex.
*
* <pre>
* FluentIterable<StorageMetadata> blobs = blobstore.list(...).concat();
* for (StorageMetadata blob : blobs) {
* process(blob);
* }
* </pre>
*
* @see Iterators#concat
*/
public FluentIterable<E> concat() {
final Iterator<IterableWithMarker<E>> iterator = iterator();
final UnmodifiableIterator<Iterator<E>> unmodifiable = new UnmodifiableIterator<Iterator<E>>() {
@Override
public boolean hasNext() {
return iterator.hasNext();
}
@Override
public Iterator<E> next() {
return iterator.next().iterator();
}
};
return new FluentIterable<E>() {
@Override
public Iterator<E> iterator() {
return Iterators.concat(unmodifiable);
}
};
}
}