JPA 手写分页方法2种数据接收方式（实体类接收数据，Map接收数据）

Dear 丶 2022-10-27 14:59 255阅读 0赞

### 1 实体类接收数据 ###

package com.dao;
    import org.hibernate.query.internal.NativeQueryImpl;
    import org.hibernate.transform.Transformers;
    import org.springframework.data.domain.Page;
    import org.springframework.data.domain.PageImpl;
    import org.springframework.data.domain.PageRequest;
    import org.springframework.data.domain.Pageable;
    import org.springframework.stereotype.Repository;
    
    import javax.persistence.EntityManager;
    import javax.persistence.PersistenceContext;
    import javax.persistence.Query;
    
    @Repository
    public class BaseDao {
    
        @PersistenceContext
        private EntityManager entityManager;
    
        /**
         * 分页方法（通用）
         *
         * @param thisClass xx类.class
         * @param selectSql select语句（不能带参数,paramType=1时参数格式为?,paramType=2时参数格式为:xxx
         * @param otherSql
         * @param params
         * @param paramType
         * @param pageNo
         * @param pageSize
         * @param <T>
         * @return
         */
        private <T> Page<T> getListByPage(Class thisClass, String selectSql, String otherSql, Object params, int paramType, int pageNo, int pageSize) {
            String countSelectSql = "select count(*) ";
            //获取数量
            String countSql = countSelectSql + " " + otherSql;
            Query countQuery = null;
            if (pageNo > 0 && pageSize > 0) {
                countQuery = entityManager.createNativeQuery(countSql);
            }
    
            int count = 0;
            if (countQuery != null) {//分页
                //填充参数
                setParameter(params,paramType,countQuery)
                Object result = countQuery.getSingleResult();
                if (null != result && !"".equals(result.toString())) {
                    count = Integer.parseInt(result.toString());
                }
            }
    
            //获取数据
            String sql = selectSql + " " + otherSql;
            Query query = this.entityManager.createNativeQuery(sql);
            //填充参数
            setParameter(params,paramType,query);
            if (countQuery != null) {//分页
                query.setFirstResult((pageNo - 1) * pageSize);
                query.setMaxResults(pageSize);
            }
            query.unwrap(NativeQueryImpl.class).setResultTransformer(Transformers.aliasToBean(thisClass));
            List<T> list = query.getResultList();
            if (countQuery != null) {//分页
                Pageable pageable = PageRequest.of(pageNo - 1, pageSize);
                return new PageImpl<T>(list, pageable, count);
            }
            return new PageImpl<T>(list);
        }
    }

### 2 Map接收数据 ###

用于需要获取动态表的数据，但是动态表没有对应的实体类的情况。

package com.dao;
    import org.hibernate.query.internal.NativeQueryImpl;
    import org.hibernate.transform.Transformers;
    import org.springframework.data.domain.Page;
    import org.springframework.data.domain.PageImpl;
    import org.springframework.data.domain.PageRequest;
    import org.springframework.data.domain.Pageable;
    import org.springframework.stereotype.Repository;
    
    import javax.persistence.EntityManager;
    import javax.persistence.PersistenceContext;
    import javax.persistence.Query;
    
    @Repository
    public class BaseDao {
    
        @PersistenceContext
        private EntityManager entityManager;
    
        /**
         * 分页方法（Map接收数据）
         *
         * @param selectSql select语句（不能带参数,paramType=1时参数格式为?,paramType=2时参数格式为:xxx
         * @param otherSql
         * @param params
         * @param paramType
         * @param pageNo
         * @param pageSize
         * @return
         */
        private Page<Map<String, Object>> getListByMapPage(String selectSql, String otherSql, Object params, int paramType, int pageNo, int pageSize) {
            String countSelectSql = "select count(*) ";
            //获取数量
            String countSql = countSelectSql + " " + otherSql;
            Query countQuery = null;
            if (pageNo > 0 && pageSize > 0) {
                countQuery = entityManager.createNativeQuery(countSql);
            }
    
            int count = 0;
            if (countQuery != null) {//分页
                //填充参数
                setParameter(params,paramType,countQuery)
                Object result = countQuery.getSingleResult();
                if (null != result && !"".equals(result.toString())) {
                    count = Integer.parseInt(result.toString());
                }
            }
    
            //获取数据
            String sql = selectSql + " " + otherSql;
            Query query = this.entityManager.createNativeQuery(sql);
            //填充参数
            setParameter(params,paramType,query);
            if (countQuery != null) {//分页
                query.setFirstResult((pageNo - 1) * pageSize);
                query.setMaxResults(pageSize);
            }
            //设置接收数据类型为Map
            query.unwrap(NativeQueryImpl.class).setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP);
            List<Map<String, Object>> list = query.getResultList();
            if (countQuery != null) {//分页
                Pageable pageable = PageRequest.of(pageNo - 1, pageSize);
                return new PageImpl<Map<String, Object>>(list, pageable, count);
            }
            return new PageImpl<Map<String, Object>>(list);
        }
    }

注：setParameter()的源码请查看以下博客。

[JPA 实现两种参数注入方式（?和:xxx）][JPA _xxx]

[JPA _xxx]: https://blog.csdn.net/qq_38974638/article/details/113714430