MongoTemplate分页参数工具类

缺乏、安全感 2023-02-25 11:26 5阅读 0赞

我们在使用mongodb的java代码的时候，分页获取数据是很常见的代码，但并没有mongo的java的工具类提供出来。这里封装一个比较简单分页工具类供大家参考。

public class MongoPageHelper {
    
        private static final int FIRST_PAGE_NUM = 1;
    
        private static final String ID = "_id";
    
        private final MongoTemplate mongoTemplate;
    
    
        public MongoPageHelper(MongoTemplate mongoTemplate) {
            this.mongoTemplate = mongoTemplate;
        }
    
        /**
         * 分页查询，直接返回集合类型的结果
         */
        public <T> PageResult<T> pageQuery(Query query, Class<T> entityClass, Integer pageSize, Integer pageNum,String collectionName) {
            return pageQuery(query, entityClass, pageSize, pageNum, Function.identity(), 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 ,确定集合
         * @param pageSize  每页大小
         * @param pageNum  当前页
         * @param mapper   映射器 collection 定义的entityClass,如要转化为另一个对象
         * @param lastId  上一页的主键id
         * @param <T>   mongo映射实体类
         * @param <R>   响应实体类
         * @return     分页参数
         */
        public <T, R> PageResult<R> pageQuery(Query query, Class<T> entityClass, Integer pageSize,
                                               Integer pageNum, Function<T, R> mapper, 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 = FIRST_PAGE_NUM;
            }
    
            if (!StringUtils.isEmpty(lastId)) {
                Criteria criteria = new Criteria();
                if (pageNum != FIRST_PAGE_NUM) {
                    criteria.and(ID).gt(new ObjectId(lastId));
                }
                query.addCriteria(criteria);
                query.limit(pageSize);
            }else {
                int skip = pageSize * (pageNum - 1);
                query.skip(skip).limit(pageSize);
            }
            List<T> entityList = mongoTemplate.find(query, entityClass, collectionName);
    
           final PageResult<R> 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;
        }
    
    }

下面演示工具类的使用

1、先查看一下原数据  
![在这里插入图片描述][20200712215658908.png]

2、代码分页工具类演示

@Autowired
        private MongoTemplate mongoTemplate;
    
    @GetMapping("/testMongoPage")
        public String testMongoPage() {
    
            MongoPageHelper mongoPageHelper = new MongoPageHelper(mongoTemplate);
            Query query = new Query();
            Sort sort = Sort.by(Sort.Direction.DESC, "valueInt");
            query.with(sort);
            Criteria criteria = new Criteria();
            criteria.and("valueInt").lt(14);
            query.addCriteria(criteria);
            PageResult<MongoTestEntity> pageResult = mongoPageHelper.pageQuery(query, MongoTestEntity.class,
                    3, 1, "mongoTest");
    
    
    
            PageResult<MongoTestEntity> pageResult2 = mongoPageHelper.pageQuery(query, MongoTestEntity.class,
                    3, 2, "mongoTest");
    
            PageResult<String> pageResult3 = mongoPageHelper.pageQuery(query, MongoTestEntity.class,
                    3, 2,MongoTestEntity::getValueStr , null, "mongoTest");
    
            System.out.println(pageResult);
            System.out.println("------------------------------");
            System.out.println(pageResult2);
            System.out.println("===============================");
            System.out.println(pageResult3);
            return “success”;
        }

3、查看结果  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZhamluZ19mZWl5dWU_size_16_color_FFFFFF_t_70]

[20200712215658908.png]: /images/20230209/aa1a2f1f18ec442aab4a81ad0248e89b.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZhamluZ19mZWl5dWU_size_16_color_FFFFFF_t_70]: /images/20230209/88d2d9ee4f2f4f828fadc4e321dce02c.png