spring data jpa(四)封装数据库关键字（EQ, L

package com.vanhr.hro.util;


import java.util.Map;
import java.util.Map.Entry;
import org.apache.commons.lang3.StringUtils;
import com.google.common.collect.Maps;

/**
 * @Auther: CHENGKEDONG
 * @Date: 2019/1/16 13:38
 * @Description:
 */
public class SearchFilter {
    public enum Operator {EQ, LIKE, GT, LT, GTE, LTE, NEQ}

    public String fieldName;
    public Object value;
    public Operator operator;

    public SearchFilter(String fieldName, Operator operator, Object value) {
        this.fieldName = fieldName;
        this.value = value;
        this.operator = operator;
    }

    /**
     * searchParams中key的格式为OPERATOR_FIELDNAME
     */
    public static Map<String, SearchFilter> parse(Map<String, Object> searchParams) {
        Map<String, SearchFilter> filters = Maps.newHashMap();
        for (Entry<String, Object> entry : searchParams.entrySet()) {
            //过滤掉空值
            String key = entry.getKey();
            Object value = entry.getValue();
            //拆分operator与filedAttribute
            String[] names = StringUtils.split(key, "_");
            if (names.length != 2) {
                throw new IllegalArgumentException(key + " is not a valid search filter name");
            }
            String filedName = names[1];
            Operator operator = Operator.valueOf(names[0]);
            //创建searchFilter
            SearchFilter filter = new SearchFilter(filedName, operator, value);
            filters.put(key, filter);
        }
        return filters;
    }

}

package com.vanhr.hro.util;

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;
import org.springside.modules.utils.Collections3;

/**
 * @Auther: CHENGKEDONG
 * @Date: 2019/1/16 13:43
 * @Description:
 */
public class DynamicSpecifications {
    public static <T> Specification<T> bySearchFilter(final Collection<SearchFilter> filters, final Class<T> entityClazz) {
        return new Specification<T>() {
            @Override
            public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
                if (Collections3.isNotEmpty(filters)) {
                    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 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 NEQ:
                                predicates.add(builder.notEqual(expression, filter.value));
                                break;
                        }
                    }
                    //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();
            }
        };
    }
}