at.molindo.esi4j.module.hibernate.scrolling.DefaultQueryScrollingSession.java Source code

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/**
 * Copyright 2010 Molindo GmbH
 *
 * Licensed 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 at.molindo.esi4j.module.hibernate.scrolling;

import java.io.Serializable;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.hibernate.Criteria;
import org.hibernate.FetchMode;
import org.hibernate.Session;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Restrictions;
import org.hibernate.internal.SessionImpl;
import org.hibernate.metadata.ClassMetadata;

public class DefaultQueryScrollingSession implements ScrollingSession {

    private final Class<?> _type;
    private Serializable _lastId;
    private Map<String, FetchMode> _fetchModes;

    public DefaultQueryScrollingSession(Class<?> type) {
        if (type == null) {
            throw new NullPointerException("type");
        }
        _type = type;
        _fetchModes = Collections.emptyMap();
    }

    public DefaultQueryScrollingSession(Class<?> type, Map<String, FetchMode> fetchModes) {
        this(type);
        _fetchModes = new HashMap<String, FetchMode>(fetchModes);
    }

    @Override
    public boolean isOrdered() {
        return true;
    }

    @Override
    public List<?> fetch(Session session, int batchSize) {
        Criteria criteria = session.createCriteria(_type);
        if (_lastId != null) {
            criteria.add(Restrictions.gt("id", _lastId));
        }
        criteria.addOrder(Order.asc("id"));
        criteria.setMaxResults(batchSize);
        criteria.setCacheable(false);

        for (Map.Entry<String, FetchMode> e : _fetchModes.entrySet()) {
            criteria.setFetchMode(e.getKey(), e.getValue());
        }

        List<?> list = criteria.list();

        if (list.size() > 0) {
            ClassMetadata meta = session.getSessionFactory().getClassMetadata(_type);

            Object last = list.get(list.size() - 1);
            _lastId = meta.getIdentifier(last, (SessionImpl) session);
        }

        return list;
    }

}