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Wudaosoft Commons Library
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/**
 *    Copyright 2009-2018 Wudao Software Studio(wudaosoft.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.wudaosoft.commons.persistence;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaBuilder.In;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Path;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.springframework.data.jpa.domain.Specification;

/**
 * @author Changsoul Wu
 *
 */
public class DynamicSpecifications {

	public static  Specification bySearchFilter(final Collection filters,
			final Class entityClazz) {

		return new Specification() {
			@Override
			public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder builder) {
				if ((filters != null) && !(filters.isEmpty())) {

					List predicates = new ArrayList(30);

					for (SearchFilter filter : filters) {
						Predicate p = buildPredicate(filter, root, builder);

						if (p != null)
							predicates.add(p);
					}

					// 将所有条件用 and 联合起来
					if (!predicates.isEmpty()) {
						return builder.and(predicates.toArray(new Predicate[predicates.size()]));
					}
				}

				return builder.conjunction();
			}
		};
	}

	@SuppressWarnings({ "rawtypes", "unchecked" })
	protected static Predicate buildPredicate(final SearchFilter filter, final Root root,
			final CriteriaBuilder builder) {

		// nested path translate, 如Task的名为"user.name"的filedName,
		// 转换为Task.user.name属性
		String[] names = filter.fieldName.split("\\.");
		Path expression = root.get(names[0]);
		for (int i = 1; i < names.length; i++) {
			expression = expression.get(names[i]);
		}

		Predicate predicate = null;

		// logic operator
		switch (filter.operator) {
		case EQ:
			predicate = builder.equal(expression, filter.value);
			break;
		case LIKE:
			predicate = builder.like(expression, "%" + filter.value + "%");
			break;
		case GT:
			predicate = builder.greaterThan(expression, (Comparable) filter.value);
			break;
		case LT:
			predicate = builder.lessThan(expression, (Comparable) filter.value);
			break;
		case GTE:
			predicate = builder.greaterThanOrEqualTo(expression, (Comparable) filter.value);
			break;
		case LTE:
			predicate = builder.lessThanOrEqualTo(expression, (Comparable) filter.value);
			break;
		case IN:
			predicate = prossIn(filter, builder, expression);
			break;
		case NOTIN:
			In