fun.bigtable.kraken.helper.MongoPageHelper Maven / Gradle / Ivy

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package fun.bigtable.kraken.helper;

import org.apache.commons.lang3.StringUtils;
import org.bson.types.ObjectId;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Sort;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.query.Criteria;
import org.springframework.data.mongodb.core.query.Query;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.function.Function;
import java.util.stream.Collectors;

/**
 */
@Component
public class MongoPageHelper {

        public static final int FIRST_PAGE_NUM = 1;
        public static final String ID = "_id";
        private final MongoTemplate mongoTemplate;


        @Autowired
        public MongoPageHelper(MongoTemplate mongoTemplate) {
            this.mongoTemplate = mongoTemplate;
        }

        /**
         * 分页查询，直接返回集合类型的结果.
         *
         * @see MongoPageHelper#pageQuery(Query,
         * Class, Function, Integer, Integer,
         * String)
         */
        public  PageResult pageQuery(Query query, Class entityClass, Integer pageSize,
                                           Integer pageNum, String collectionName) {
            return pageQuery(query, entityClass, Function.identity(), pageSize, pageNum, null, collectionName);
        }

        /**
         * 分页查询，不考虑条件分页，直接使用skip-limit来分页.
         *
         * @see MongoPageHelper#pageQuery(Query,
         * Class, Function, Integer, Integer,
         * String)
         */
        public  PageResult pageQuery(Query query, Class entityClass, Function mapper,
                                              Integer pageSize, Integer pageNum, String collectionName) {
            return pageQuery(query, entityClass, mapper, pageSize, pageNum, null, collectionName);
        }

        /**
         * 分页查询.
         *
         * @param query Mongo Query对象，构造你自己的查询条件.
         * @param entityClass Mongo collection定义的entity class，用来确定查询哪个集合.
         * @param mapper 映射器，你从db查出来的list的元素类型是entityClass, 如果你想要转换成另一个对象，比如去掉敏感字段等，可以使用mapper来决定如何转换.
         * @param pageSize 分页的大小.
         * @param pageNum 当前页.
         * @param lastId 条件分页参数, 区别于skip-limit，采用find(_id>lastId).limit分页.
         * 如果不跳页，像朋友圈，微博这样下拉刷新的分页需求，需要传递上一页的最后一条记录的ObjectId。 如果是null，则返回pageNum那一页.
         * @param  collection定义的class类型.
         * @param  最终返回时，展现给页面时的一条记录的类型。
         * @return PageResult，一个封装page信息的对象.
         */
        public  PageResult pageQuery(Query query, Class entityClass, Function mapper,
                                              Integer pageSize, Integer pageNum, String lastId, String collectionName) {
            //分页逻辑
            long total = mongoTemplate.count(query, entityClass, collectionName);
            final Integer pages = (int) Math.ceil(total / (double) pageSize);
            if (pageNum <= 0 || pageNum > pages) {
                pageNum = FIRST_PAGE_NUM;
            }
            final Criteria criteria = new Criteria();
            if (StringUtils.isNotBlank(lastId)) {
                if (pageNum != FIRST_PAGE_NUM) {
                    criteria.and(ID).gt(new ObjectId(lastId));
                }
                query.limit(pageSize);
            } else {
                int skip = pageSize * (pageNum - 1);
                query.skip(skip).limit(pageSize);
            }

            final List entityList = mongoTemplate
                    .find(query.addCriteria(criteria)
                                    .with(Sort.by(new Sort.Order(Sort.Direction.ASC, ID))),
                            entityClass,collectionName);

            final PageResult pageResult = new PageResult<>();
            pageResult.setTotal(total);
            pageResult.setPages(pages);
            pageResult.setPageSize(pageSize);
            pageResult.setPageNum(pageNum);
            pageResult.setList(entityList.stream().map(mapper).collect(Collectors.toList()));
            return pageResult;
        }

    }