| /* |
| * 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.openjpa.lib.rop; |
| |
| import java.io.ObjectStreamException; |
| import java.util.ArrayList; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.ListIterator; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * Lazy forward-only result list. |
| * |
| * @author Abe White |
| */ |
| public class LazyForwardResultList extends AbstractSequentialResultList |
| implements ResultList { |
| |
| private static final int OPEN = 0; |
| private static final int CLOSED = 1; |
| private static final int FREED = 2; |
| |
| private ResultObjectProvider _rop = null; |
| private final List _list = new ArrayList(); |
| private int _state = OPEN; |
| private int _size = -1; |
| |
| public LazyForwardResultList(ResultObjectProvider rop) { |
| _rop = rop; |
| try { |
| _rop.open(); |
| } catch (RuntimeException re) { |
| close(); |
| throw re; |
| } catch (Exception e) { |
| close(); |
| _rop.handleCheckedException(e); |
| } |
| } |
| |
| public boolean isProviderOpen() { |
| return _state == OPEN; |
| } |
| |
| public boolean isClosed() { |
| return _state == CLOSED; |
| } |
| |
| public void close() { |
| if (_state != CLOSED) { |
| free(); |
| _state = CLOSED; |
| } |
| } |
| |
| public Object get(int index) { |
| assertOpen(); |
| |
| // optimization for getting sequntially |
| if (index == _list.size()) |
| addNext(); |
| if (index < _list.size()) |
| return _list.get(index); |
| |
| return super.get(index); |
| } |
| |
| protected ListIterator itr(int index) { |
| return (_state != OPEN) ? _list.listIterator(index) : new Itr(index); |
| } |
| |
| public int size() { |
| assertOpen(); |
| if (_size != -1) |
| return _size; |
| if (_state != OPEN) |
| return _list.size(); |
| try { |
| _size = _rop.size(); |
| return _size; |
| } catch (RuntimeException re) { |
| close(); |
| throw re; |
| } catch (Exception e) { |
| close(); |
| _rop.handleCheckedException(e); |
| return -1; |
| } |
| } |
| |
| private boolean addNext() { |
| try { |
| if (!_rop.next()) { |
| free(); |
| return false; |
| } |
| _list.add(_rop.getResultObject()); |
| return true; |
| } catch (RuntimeException re) { |
| close(); |
| throw re; |
| } catch (Exception e) { |
| close(); |
| _rop.handleCheckedException(e); |
| return false; |
| } |
| } |
| |
| private void free() { |
| if (_state == OPEN) { |
| try { |
| _rop.close(); |
| } catch (Exception e) { |
| } |
| _state = FREED; |
| } |
| } |
| |
| public Object writeReplace() throws ObjectStreamException { |
| // fully traverse results |
| if (_state == OPEN) |
| for (Iterator itr = itr(_list.size()); itr.hasNext();) |
| itr.next(); |
| return _list; |
| } |
| |
| public int hashCode() { |
| // superclass tries to traverses entire list for hashcode |
| return System.identityHashCode(this); |
| } |
| |
| public boolean equals(Object other) { |
| // superclass tries to traverse entire list for equality |
| return other == this; |
| } |
| |
| public List subList(int fromIndex, int toIndex) { |
| assertOpen(); |
| return _list.subList(fromIndex, toIndex); |
| } |
| |
| private class Itr extends AbstractListIterator { |
| |
| private int _idx = 0; |
| |
| public Itr(int index) { |
| _idx = Math.min(index, _list.size()); |
| while (_idx < index) |
| next(); |
| } |
| |
| public int nextIndex() { |
| return _idx; |
| } |
| |
| public int previousIndex() { |
| return _idx - 1; |
| } |
| |
| public boolean hasNext() { |
| if (_list.size() > _idx) |
| return true; |
| if (_state != OPEN) |
| return false; |
| return addNext(); |
| } |
| |
| public boolean hasPrevious() { |
| return _idx > 0; |
| } |
| |
| public Object previous() { |
| if (_idx == 0) |
| throw new NoSuchElementException(); |
| return _list.get(--_idx); |
| } |
| |
| public Object next() { |
| if (!hasNext()) |
| throw new NoSuchElementException(); |
| return _list.get(_idx++); |
| } |
| } |
| } |