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This API allows you to construct Query By Example using the JPA 2 Criteria API.

There is a newer version: 1.0.1

/*
 * Copyright 2015 JAXIO http://www.jaxio.com
 *
 * 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 com.jaxio.jpa.querybyexample;

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Singleton;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.Expression;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;
import javax.persistence.metamodel.EntityType;
import javax.persistence.metamodel.SingularAttribute;
import java.util.List;

import static com.google.common.collect.Lists.newArrayList;
import static javax.persistence.metamodel.Attribute.PersistentAttributeType.MANY_TO_ONE;
import static javax.persistence.metamodel.Attribute.PersistentAttributeType.ONE_TO_ONE;

@Named
@Singleton
public class ByPatternUtil {
    @PersistenceContext
    private EntityManager em;
    @Inject
    private JpaUtil jpaUtil;

    /*
     * Lookup entities having at least one String attribute matching the passed sp's pattern
     */
    @SuppressWarnings("unchecked")
    public  Predicate byPattern(Root root, CriteriaBuilder builder, SearchParameters sp, Class type) {
        if (!sp.hasSearchPattern()) {
            return null;
        }

        List predicates = newArrayList();
        EntityType entity = em.getMetamodel().entity(type);
        String pattern = sp.getSearchPattern();

        for (SingularAttribute attr : entity.getSingularAttributes()) {
            if (attr.getPersistentAttributeType() == MANY_TO_ONE || attr.getPersistentAttributeType() == ONE_TO_ONE) {
                continue;
            }

            if (attr.getJavaType() == String.class) {
                predicates.add(jpaUtil.stringPredicate((Expression) root.get(jpaUtil.attribute(entity, attr)), pattern, sp, builder));
            }
        }

        return jpaUtil.orPredicate(builder, predicates);
    }
}