/*
* 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 org.apache.jackrabbit.rmi.server.iterator;
import java.rmi.RemoteException;
import java.util.ArrayList;
import java.util.NoSuchElementException;
import javax.jcr.RangeIterator;
import org.apache.jackrabbit.rmi.remote.RemoteIterator;
import org.apache.jackrabbit.rmi.server.RemoteAdapterFactory;
import org.apache.jackrabbit.rmi.server.ServerObject;
/**
* Remote adapter for the JCR {@link RangeIterator} interface. This
* class makes a local iterator available as an RMI service using the
* {@link RemoteIterator} interface.
*/
public abstract class ServerIterator extends ServerObject
implements RemoteIterator {
/** The adapted local iterator. */
private final RangeIterator iterator;
/** The maximum number of elements to send per request. */
private final int maxBufferSize;
/**
* The cached number of elements in the iterator, -1 if the iterator
* size is unknown, or -2 if the size has not been retrieved from the
* adapted local iterator. This variable is useful in cases when the
* underlying iterator does not know its sizes (getSize() returns -1)
* but we reach the end of the iterator in a nextObjects() call and
* can thus determine the size of the iterator.
*/
private long size;
/**
* Creates a remote adapter for the given local item.
*
* @param iterator local iterator to be adapted
* @param factory remote adapter factory
* @param maxBufferSize maximum buffer size
* @throws RemoteException on RMI errors
*/
public ServerIterator(
RangeIterator iterator, RemoteAdapterFactory factory,
int maxBufferSize) throws RemoteException {
super(factory);
this.iterator = iterator;
this.maxBufferSize = maxBufferSize;
this.size = -2;
}
/**
* Returns the size of the iterator. The size is cached by invoking the
* adapted local iterator when this method is first called or by
* determining the size from an end-of-iterator condition in nextObjects().
*
* @return size of the iterator
* @throws RemoteException on RMI errors
*/
@Override
public long getSize() throws RemoteException {
if (size == -2) {
size = iterator.getSize();
}
return size;
}
/**
* Skips the given number of elements.
*
* @param items number of elements to skip
* @throws NoSuchElementException if skipped past the last element
* @throws RemoteException on RMI errors
*/
@Override
public void skip(long items)
throws NoSuchElementException, RemoteException {
try {
iterator.skip(items);
} catch (NoSuchElementException e) {
throw new NoSuchElementException(e.getMessage());
}
}
/**
* Returns a remote adapter for the given local object. This abstract
* method is used by {@link #nextObjects()} to convert the local
* objects to remote references to be sent to the client.
* <p>
* Subclasses should implement this method to use the remote adapter
* factory to create remote adapters of the specific element type.
*
* @param object local object
* @return remote adapter
* @throws RemoteException on RMI errors
*/
protected abstract Object getRemoteObject(Object object)
throws RemoteException;
/**
* Returns an array of remote references to the next elements in this
* iteration.
*
* @return array of remote references, or <code>null</code>
* @throws RemoteException on RMI errors
*/
@Override
public Object[] nextObjects() throws RemoteException {
ArrayList items = new ArrayList();
while (items.size() < maxBufferSize && iterator.hasNext()) {
items.add(getRemoteObject(iterator.next()));
}
if (items.size() > 0) {
return items.toArray(new Object[items.size()]);
} else {
size = iterator.getPosition();
return null;
}
}
}