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OpenJPA Utilities Library
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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 org.apache.openjpa.lib.rop;

import java.util.Iterator;
import java.util.NoSuchElementException;

import org.apache.openjpa.lib.util.Closeable;

/**
 * Iterator wrapped around a {@link ResultObjectProvider}.
 *
 * @author Abe White
 */
public class ResultObjectProviderIterator implements Iterator, Closeable {

    private final ResultObjectProvider _rop;
    private Boolean _hasNext = null;
    private Boolean _open = null;

    /**
     * Constructor. Supply object provider.
     */
    public ResultObjectProviderIterator(ResultObjectProvider rop) {
        _rop = rop;
    }

    /**
     * Close the underlying result object provider.
     */
    @Override
    public void close() {
        if (Boolean.TRUE.equals(_open)) {
            try {
                _rop.close();
            } catch (Exception e) {
            }
            _open = Boolean.FALSE;
        }
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean hasNext() {
        if (Boolean.FALSE.equals(_open))
            return false;

        if (_hasNext == null) {
            try {
                if (_open == null) {
                    _rop.open();
                    _open = Boolean.TRUE;
                }
                _hasNext = (_rop.next()) ? Boolean.TRUE : Boolean.FALSE;
            } catch (RuntimeException re) {
                close();
                throw re;
            } catch (Exception e) {
                close();
                _rop.handleCheckedException(e);
                return false;
            }
        }

        // close if we reach the end of the list
        if (!_hasNext) {
            close();
            return false;
        }
        return true;
    }

    @Override
    public Object next() {
        if (!hasNext())
            throw new NoSuchElementException();
        try {
            Object ret = _rop.getResultObject();
            _hasNext = null;
            return ret;
        } catch (RuntimeException re) {
            close();
            throw re;
        } catch (Exception e) {
            close();
            _rop.handleCheckedException(e);
            return null;
        }
    }

    @Override
    protected void finalize() {
        close();
    }
}