org.springframework.batch.item.database.HibernateItemReaderHelper.java Source code

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/*
 * Copyright 2006-2013 the original author or authors.
 *
 * 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 org.springframework.batch.item.database;

import java.util.Collection;
import java.util.List;
import java.util.Map;

import org.hibernate.Query;
import org.hibernate.ScrollMode;
import org.hibernate.ScrollableResults;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.StatelessSession;
import org.springframework.batch.item.database.orm.HibernateQueryProvider;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Internal shared state helper for hibernate readers managing sessions and
 * queries.
 *
 * @author Dave Syer
 *
 */
public class HibernateItemReaderHelper<T> implements InitializingBean {

    private SessionFactory sessionFactory;

    private String queryString = "";

    private String queryName = "";

    private HibernateQueryProvider queryProvider;

    private boolean useStatelessSession = true;

    private StatelessSession statelessSession;

    private Session statefulSession;

    /**
     * @param queryName name of a hibernate named query
     */
    public void setQueryName(String queryName) {
        this.queryName = queryName;
    }

    /**
     * @param queryString HQL query string
     */
    public void setQueryString(String queryString) {
        this.queryString = queryString;
    }

    /**
     * @param queryProvider Hibernate query provider
     */
    public void setQueryProvider(HibernateQueryProvider queryProvider) {
        this.queryProvider = queryProvider;
    }

    /**
     * Can be set only in uninitialized state.
     *
     * @param useStatelessSession <code>true</code> to use
     * {@link StatelessSession} <code>false</code> to use standard hibernate
     * {@link Session}
     */
    public void setUseStatelessSession(boolean useStatelessSession) {
        Assert.state(statefulSession == null && statelessSession == null,
                "The useStatelessSession flag can only be set before a session is initialized.");
        this.useStatelessSession = useStatelessSession;
    }

    /**
     * @param sessionFactory hibernate session factory
     */
    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    @Override
    public void afterPropertiesSet() throws Exception {

        Assert.state(sessionFactory != null, "A SessionFactory must be provided");

        if (queryProvider == null) {
            Assert.notNull(sessionFactory, "session factory must be set");
            Assert.state(StringUtils.hasText(queryString) ^ StringUtils.hasText(queryName),
                    "queryString or queryName must be set");
        }
        // making sure that the appropriate (Hibernate) query provider is set
        else {
            Assert.state(queryProvider != null, "Hibernate query provider must be set");
        }

    }

    /**
     * Get a cursor over all of the results, with the forward-only flag set.
     *
     * @param fetchSize the fetch size to use retrieving the results
     * @param parameterValues the parameter values to use (or null if none).
     *
     * @return a forward-only {@link ScrollableResults}
     */
    public ScrollableResults getForwardOnlyCursor(int fetchSize, Map<String, Object> parameterValues) {
        Query query = createQuery();
        if (parameterValues != null) {
            query.setProperties(parameterValues);
        }
        return query.setFetchSize(fetchSize).scroll(ScrollMode.FORWARD_ONLY);
    }

    /**
     * Open appropriate type of hibernate session and create the query.
     */
    public Query createQuery() {

        if (useStatelessSession) {
            if (statelessSession == null) {
                statelessSession = sessionFactory.openStatelessSession();
            }
            if (queryProvider != null) {
                queryProvider.setStatelessSession(statelessSession);
            } else {
                if (StringUtils.hasText(queryName)) {
                    return statelessSession.getNamedQuery(queryName);
                } else {
                    return statelessSession.createQuery(queryString);
                }
            }
        } else {
            if (statefulSession == null) {
                statefulSession = sessionFactory.openSession();
            }
            if (queryProvider != null) {
                queryProvider.setSession(statefulSession);
            } else {
                if (StringUtils.hasText(queryName)) {
                    return statefulSession.getNamedQuery(queryName);
                } else {
                    return statefulSession.createQuery(queryString);
                }
            }
        }

        // If queryProvider is set use it to create a query
        return queryProvider.createQuery();

    }

    /**
     * Scroll through the results up to the item specified.
     *
     * @param cursor the results to scroll over
     */
    public void jumpToItem(ScrollableResults cursor, int itemIndex, int flushInterval) {
        for (int i = 0; i < itemIndex; i++) {
            cursor.next();
            if (i % flushInterval == 0 && !useStatelessSession) {
                statefulSession.clear(); // Clears in-memory cache
            }
        }
    }

    /**
     * Close the open session (stateful or otherwise).
     */
    public void close() {
        if (statelessSession != null) {
            statelessSession.close();
            statelessSession = null;
        }
        if (statefulSession != null) {
            statefulSession.close();
            statefulSession = null;
        }
    }

    /**
     * Read a page of data, clearing the existing session (if necessary) first,
     * and creating a new session before executing the query.
     *
     * @param page the page to read (starting at 0)
     * @param pageSize the size of the page or maximum number of items to read
     * @param fetchSize the fetch size to use
     * @param parameterValues the parameter values to use (if any, otherwise
     * null)
     * @return a collection of items
     */
    public Collection<? extends T> readPage(int page, int pageSize, int fetchSize,
            Map<String, Object> parameterValues) {

        clear();

        Query query = createQuery();
        if (parameterValues != null) {
            query.setProperties(parameterValues);
        }
        @SuppressWarnings("unchecked")
        List<T> result = query.setFetchSize(fetchSize).setFirstResult(page * pageSize).setMaxResults(pageSize)
                .list();
        return result;

    }

    /**
     * Clear the session if stateful.
     */
    public void clear() {
        if (statefulSession != null) {
            statefulSession.clear();
        }
    }

}