de.tudarmstadt.ukp.csniper.webapp.security.dao.AbstractDao.java Source code

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/*******************************************************************************
 * Copyright 2013
 * Ubiquitous Knowledge Processing (UKP) Lab
 * Technische Universitt Darmstadt
 * 
 * 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 de.tudarmstadt.ukp.csniper.webapp.security.dao;

import java.beans.PropertyDescriptor;
import java.util.ArrayList;
import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.springframework.beans.BeanWrapper;
import org.springframework.beans.PropertyAccessorFactory;
import org.springframework.transaction.annotation.Transactional;

public abstract class AbstractDao<T, K> {
    @PersistenceContext
    protected EntityManager entityManager;

    @Transactional
    public void create(final T aModel) {
        entityManager.persist(aModel);
        entityManager.flush();
    }

    @Transactional
    public T update(final T aModel) {
        return entityManager.merge(aModel);
    }

    public abstract int delete(final K aId);

    @Transactional
    public <TT> List<TT> getUnique(Class<?> aType, String aProperty, Class<TT> aPropertyType) {
        return entityManager.createQuery(
                "SELECT DISTINCT o." + aProperty + " FROM " + aType.getName() + " o ORDER BY o." + aProperty,
                aPropertyType).getResultList();
    }

    /**
     * Finds all entities that have the same type as the given example and all fields are equal to
     * non-null fields in the example.
     */
    protected <TT> CriteriaQuery<TT> queryByExample(TT aExample, String aOrderBy, boolean aAscending) {
        CriteriaBuilder cb = entityManager.getCriteriaBuilder();
        @SuppressWarnings("unchecked")
        CriteriaQuery<TT> query = cb.createQuery((Class<TT>) aExample.getClass());
        @SuppressWarnings("unchecked")
        Root<TT> root = query.from((Class<TT>) aExample.getClass());
        query.select(root);

        List<Predicate> predicates = new ArrayList<Predicate>();
        BeanWrapper a = PropertyAccessorFactory.forBeanPropertyAccess(aExample);

        // Iterate over all properties
        for (PropertyDescriptor d : a.getPropertyDescriptors()) {
            Object value = a.getPropertyValue(d.getName());

            // Only consider writeable properties. This filters out e.g. the "class" (getClass())
            // property.
            if (value != null && a.isWritableProperty(d.getName())) {
                predicates.add(cb.equal(root.get(d.getName()), value));
            }
        }

        if (!predicates.isEmpty()) {
            query.where(predicates.toArray(new Predicate[predicates.size()]));
        }

        if (aOrderBy != null) {
            if (aAscending) {
                query.orderBy(cb.asc(root.get(aOrderBy)));
            } else {
                query.orderBy(cb.desc(root.get(aOrderBy)));
            }
        }

        return query;
    }
}