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

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Here is the source code for at.molindo.esi4j.module.hibernate.scrolling.CustomQueryScrollingSession.java

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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.util.List;

import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;

public class CustomQueryScrollingSession implements ScrollingSession {

    private final QueryProvider _queryProvider;

    private int _next = 0;

    private final Class<?> _type;

    public CustomQueryScrollingSession(Class<?> type, QueryProvider queryProvider) {
        if (type == null) {
            throw new NullPointerException("type");
        }
        if (queryProvider == null) {
            throw new NullPointerException("queryProvider");
        }
        _type = type;
        _queryProvider = queryProvider;
    }

    @Override
    public boolean isOrdered() {
        return _queryProvider.isOrdered();
    }

    @Override
    public List<?> fetch(Session session, int batchSize) {
        List<?> list;

        Criteria criteria = _queryProvider.createCriteria(_type, session);
        if (criteria != null) {
            list = fetch(criteria, _next, batchSize);
        } else {
            Query query = _queryProvider.createQuery(_type, session);
            list = fetch(query, _next, batchSize);
        }

        _next += list.size();

        return list;
    }

    private List<?> fetch(Criteria criteria, int first, int max) {
        // TODO there are better ways to scroll than setFirstResult(..)
        return criteria.setFirstResult(first).setMaxResults(max).setCacheable(false).list();
    }

    private List<?> fetch(Query query, int first, int max) {
        // TODO there are better ways to scroll than setFirstResult(..)
        return query.setFirstResult(first).setMaxResults(max).setCacheable(false).list();
    }

}