edu.utah.further.core.data.hibernate.hql.HqlQueryBuilderImpl.java Source code

Introduction

Here is the source code for edu.utah.further.core.data.hibernate.hql.HqlQueryBuilderImpl.java

Source

/**
 * Copyright (C) [2013] [The FURTHeR Project]
 *
 * 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 edu.utah.further.core.data.hibernate.hql;

import static edu.utah.further.core.api.collections.CollectionUtil.newMap;
import static org.slf4j.LoggerFactory.getLogger;

import java.util.Map;

import org.hibernate.Query;
import org.hibernate.Session;
import org.slf4j.Logger;

import edu.utah.further.core.api.data.PersistentEntity;
import edu.utah.further.core.api.exception.ApplicationException;
import edu.utah.further.core.api.text.StringUtil;

/**
 * Implements the builder pattern to construct an HQL query from snippets that represent
 * the main query and selection criteria.
 * <p>
 * -----------------------------------------------------------------------------------<br>
 * (c) 2008-2013 FURTHeR Project, Health Sciences IT, University of Utah<br>
 * Contact: {@code <further@utah.edu>}<br>
 * Biomedical Informatics, 26 South 2000 East<br>
 * Room 5775 HSEB, Salt Lake City, UT 84112<br>
 * Day Phone: 1-801-581-4080<br>
 * -----------------------------------------------------------------------------------
 *
 * @author Oren E. Livne {@code <oren.livne@utah.edu>}
 * @version May 29, 2009
 */
public final class HqlQueryBuilderImpl implements HqlQueryBuilder {
    // ========================= CONSTANTS =================================

    /**
     * A logger that helps identify this class' printouts.
     */
    @SuppressWarnings("unused")
    private static final Logger log = getLogger(HqlQueryBuilderImpl.class);

    /**
     * Add this string before the first criterion only.
     */
    private static final String CRITERION_PREFIX = " where ";

    /**
     * Add this string before every criterion except the first one.
     */
    private static final String CRITERION_DELIMITER = " and ";

    // ========================= FIELDS ====================================

    /**
     * Keeps track of progress while building the HQL query string.
     */
    private StringBuilder hqlBuilder = StringUtil.newStringBuilder();

    /**
     * Keeps track of parametric substitution entities in the HQL query.
     */
    private final Map<String, PersistentEntity<?>> entitiesToSet = newMap();

    /**
     * A guard that keeps track of whether HQL query was already appended.
     */
    private boolean appendedQuery = false;

    /**
     * Keeps track of criteria state: whether this is the first criterion or not.
     */
    private boolean firstCriterion = true;

    // ========================= METHODS ===================================

    /**
     * Append the main query.
     *
     * @param query
     *            HQL query string
     * @return this object, for method call chaining
     * @see edu.utah.further.core.data.hibernate.hql.HqlQueryBuilder#appendQuery(java.lang.String)
     */
    @Override
    public HqlQueryBuilder appendQuery(final String query) {
        // Update flags
        if (appendedQuery) {
            throw new ApplicationException("Cannot append more than one query");
        }
        appendedQuery = true;

        // Prepend the builder with the query string
        hqlBuilder = new StringBuilder(query).append(hqlBuilder);
        return this;
    }

    /**
     * Append a <code>WHERE</code>-clause criterion.
     *
     * @param criterion
     *            <code>WHERE</code>-clause criterion
     * @return this object, for method call chaining
     * @see edu.utah.further.core.data.hibernate.hql.HqlQueryBuilder#appendCriterion(java.lang.String)
     */
    @Override
    public HqlQueryBuilder appendCriterion(final String criterion) {
        // Append criterion snippet
        hqlBuilder.append(firstCriterion ? CRITERION_PREFIX : CRITERION_DELIMITER).append("(").append(criterion)
                .append(")");
        // Update flags
        if (firstCriterion) {
            firstCriterion = false;
        }

        return this;
    }

    /**
     * Add a parametric entity entry.
     *
     * @param name
     *            entry name in the query
     * @param object
     *            persistent entity
     * @return this object, for method call chaining
     */
    @Override
    public HqlQueryBuilder setEntity(final String name, final PersistentEntity<?> object) {
        entitiesToSet.put(name, object);
        return this;
    }

    /**
     * Produce the HQL query.
     *
     * @param session
     *            Hibernate session
     * @return HQL query
     * @see edu.utah.further.core.data.hibernate.hql.HqlQueryBuilder#toHqlQuery(org.hibernate.Session)
     */
    @Override
    public Query toHqlQuery(final Session session) {
        final Query query = session.createQuery(hqlBuilder.toString());
        for (final Map.Entry<String, PersistentEntity<?>> entry : entitiesToSet.entrySet()) {
            query.setEntity(entry.getKey(), entry.getValue());
        }
        return query;
    }

    // ========================= PRIVATE METHODS ===========================

}