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A library of classes shared across the Eureka! Clinical platform.
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package org.eurekaclinical.standardapis.dao;

/*-
 * #%L
 * Eureka! Clinical Standard APIs
 * %%
 * Copyright (C) 2016 Emory University
 * %%
 * 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.
 * #L%
 */

import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.NoResultException;
import javax.persistence.NonUniqueResultException;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Path;
import javax.persistence.criteria.Root;
import javax.persistence.metamodel.SingularAttribute;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 *
 * @author Andrew Post
 */
public final class DatabaseSupport {

    private static Logger LOGGER
            = LoggerFactory.getLogger(DatabaseSupport.class);

    private final EntityManager entityManager;

    public DatabaseSupport(EntityManager entityManager) {
        this.entityManager = entityManager;
    }

    public  List getAll(Class entity) {
        CriteriaBuilder builder = entityManager.getCriteriaBuilder();
        CriteriaQuery criteriaQuery
                = builder.createQuery(entity);
        criteriaQuery.from(entity);
        TypedQuery typedQuery
                = entityManager.createQuery(criteriaQuery);
        List jobs = typedQuery.getResultList();
        return jobs;
    }

    public  T getUniqueByAttribute(Class entityCls,
            SingularAttribute attribute, Y value) {
        TypedQuery query = createTypedQuery(entityCls, attribute, value);
        T result = null;
        try {
            result = query.getSingleResult();
        } catch (NonUniqueResultException nure) {
            LOGGER.warn("Result not unique for {} = {}", attribute, value);
        } catch (NoResultException nre) {
            LOGGER.debug("Result not existant for {} = {}", attribute, value);
        }
        return result;
    }
    
    public  T getUniqueByAttribute(Class entityCls,
            String attributeName, Y value) {
        TypedQuery query = createTypedQuery(entityCls, attributeName, value);
        T result = null;
        try {
            result = query.getSingleResult();
        } catch (NonUniqueResultException nure) {
            LOGGER.warn("Result not unique for {} = {}", attributeName, value);
        } catch (NoResultException nre) {
            LOGGER.debug("Result not existant for {} = {}", attributeName, value);
        }
        return result;
    }

    public  List getListByAttribute(
            Class entityCls, SingularAttribute attribute, Y value) {
        TypedQuery query = createTypedQuery(entityCls, attribute, value);
        return query.getResultList();
    }

    /**
     * Creates a typed query based on the attribute given and the target value
     * for that attribute.
     *
     * @param attribute The attribute to compare.
     * @param value The target value for the given attribute.
     * @param  The type of the target attribute and target value.
     * @return A typed query that contains the given criteria.
     */
    private  TypedQuery createTypedQuery(Class entityCls,
            SingularAttribute attribute, Y value) {
        CriteriaBuilder builder = entityManager.getCriteriaBuilder();
        CriteriaQuery criteriaQuery = builder.createQuery(entityCls);
        Root root = criteriaQuery.from(entityCls);
        Path path = root.get(attribute);
        return entityManager.createQuery(criteriaQuery.where(
                builder.equal(path, value)));
    }
    
    /**
     * Creates a typed query based on the attribute given and the target value
     * for that attribute.
     *
     * @param attribute The attribute to compare.
     * @param value The target value for the given attribute.
     * @param  The type of the target attribute and target value.
     * @return A typed query that contains the given criteria.
     */
    private  TypedQuery createTypedQuery(Class entityCls,
            String attributeName, Y value) {
        CriteriaBuilder builder = entityManager.getCriteriaBuilder();
        CriteriaQuery criteriaQuery = builder.createQuery(entityCls);
        Root root = criteriaQuery.from(entityCls);
        Path path = root.get(attributeName);
        return entityManager.createQuery(criteriaQuery.where(
                builder.equal(path, value)));
    }
}