de.egore911.persistence.selector.AbstractSelector.java Source code

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Here is the source code for de.egore911.persistence.selector.AbstractSelector.java

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/*
 * Copyright 2013-2015  Christoph Brill <egore911@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package de.egore911.persistence.selector;

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

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.persistence.EntityManager;
import javax.persistence.NoResultException;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Order;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.apache.commons.lang3.StringUtils;

import de.egore911.persistence.util.EntityManagerUtil;

/**
 * @author Christoph Brill &lt;egore911@gmail.com&gt;
 */
public abstract class AbstractSelector<T> implements Serializable {

    private static final long serialVersionUID = 3479024193093886962L;

    private TypedQuery<T> buildQuery() {
        EntityManager em = EntityManagerUtil.getEntityManager();
        CriteriaBuilder builder = em.getCriteriaBuilder();
        CriteriaQuery<T> cq = builder.createQuery(getEntityClass());
        Root<T> from = cq.from(getEntityClass());
        List<Predicate> predicates = generatePredicateList(builder, from, cq);
        cq.where(predicates.toArray(new Predicate[predicates.size()]));
        cq.orderBy(generateOrderList(builder, from));
        cq.select(from);
        return em.createQuery(cq);
    }

    @Nonnull
    public List<T> findAll() {
        TypedQuery<T> q = buildQuery();
        if (limit != null) {
            q.setMaxResults(limit);
        }
        if (offset != null) {
            q.setFirstResult(offset);
        }
        return q.getResultList();
    }

    @Nullable
    public T find() {
        TypedQuery<T> q = buildQuery();
        try {
            return q.getSingleResult();
        } catch (NoResultException e) {
            return null;
        }
    }

    public long count() {
        EntityManager em = EntityManagerUtil.getEntityManager();
        CriteriaBuilder builder = em.getCriteriaBuilder();
        CriteriaQuery<Long> cq = builder.createQuery(Long.class);
        Root<T> from = cq.from(getEntityClass());
        List<Predicate> predicates = generatePredicateList(builder, from, cq);
        cq.where(predicates.toArray(new Predicate[predicates.size()]));
        cq.select(builder.count(from));
        TypedQuery<Long> q = em.createQuery(cq);
        return q.getSingleResult();
    }

    @Nonnull
    protected abstract Class<T> getEntityClass();

    @Nonnull
    protected abstract List<Predicate> generatePredicateList(@Nonnull CriteriaBuilder builder,
            @Nonnull Root<T> from, @Nonnull CriteriaQuery<?> criteriaQuery);

    @Nonnull
    protected List<Order> generateOrderList(@Nonnull CriteriaBuilder builder, @Nonnull Root<T> from) {
        if (StringUtils.isNotEmpty(sortColumn)) {
            if (!Boolean.FALSE.equals(ascending)) {
                return Collections.singletonList(builder.asc(from.get(sortColumn)));
            }
            return Collections.singletonList(builder.desc(from.get(sortColumn)));
        }
        return getDefaultOrderList(builder, from);
    }

    @SuppressWarnings("unused")
    protected List<Order> getDefaultOrderList(@Nonnull CriteriaBuilder builder, @Nonnull Root<T> from) {
        return Collections.emptyList();
    }

    private Integer offset;
    private Integer limit;
    private String sortColumn;
    private Boolean ascending;

    public AbstractSelector<T> withOffset(Integer offset) {
        this.offset = offset;
        return this;
    }

    public AbstractSelector<T> withLimit(Integer limit) {
        this.limit = limit;
        return this;
    }

    public AbstractSelector<T> withSortColumn(String sortColumn) {
        this.sortColumn = sortColumn;
        return this;
    }

    public AbstractSelector<T> withAscending(Boolean ascending) {
        this.ascending = ascending;
        return this;
    }

}