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/* 
 * Copyright(c)2010-2014 WUDAOSOFT.COM
 * 
 * Email:[email protected]
 * 
 * QQ:275100589
 */ 
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.apache.commons.lang3.StringUtils;
import org.springframework.data.jpa.domain.Specification;

import com.google.common.collect.Lists;

/**
 * @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 = Lists.newArrayList();
					
					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 = StringUtils.split(filter.fieldName, ".");
		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