jsgkj/gkaq/yjpt-java/trunk/java_src/com/jtgh/yjpt/common/DynamicSpecifications.java

package com.jtgh.yjpt.common;

import java.util.Collection;
import java.util.List;

import javax.persistence.criteria.CriteriaBuilder;
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;

@SuppressWarnings({ "rawtypes", "unchecked" })
public class DynamicSpecifications {
	public static <T> Specification<T> bySearchFilter(final Collection<SearchFilter> filters,
			final Class<T> clazz) {
		return new Specification<T>() {
			@Override
			public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query,
					CriteriaBuilder builder) {
				if (filters != null && !(filters.isEmpty())) {

					List<Predicate> predicates = Lists.newArrayList();
					for (SearchFilter filter : filters) {
						// 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]);
						}
						// logic operator
						switch (filter.operator) {
						case EQ:
							predicates.add(builder.equal(expression, filter.value));
							break;
						case LIKE:
							predicates.add(builder.like(expression, "%" + filter.value + "%"));
							break;
						case LIKE_L:
							predicates.add(builder.like(expression, "%" + filter.value));
							break;
						case LIKE_R:
							predicates.add(builder.like(expression, filter.value + "%"));
							break;
						case GT:
							predicates.add(builder.greaterThan(expression,
									(Comparable) filter.value));
							break;
						case LT:
							predicates.add(builder.lessThan(expression, (Comparable) filter.value));
							break;
						case GTE:
							predicates.add(builder.greaterThanOrEqualTo(expression,
									(Comparable) filter.value));
							break;
						case LTE:
							predicates.add(builder.lessThanOrEqualTo(expression,
									(Comparable) filter.value));
							break;
						case NL:
							predicates.add(builder.isNull(expression));
							break;
						}
					}

					// 将所有条件用 and 联合起来
					if (predicates.size() > 0) {
						return builder.and(predicates.toArray(new Predicate[predicates.size()]));
					}
				}

				return builder.conjunction();
			}
		};
	}
}