SpringDataJpa使用原生sql(EntityManager)動態拼接,分頁查詢

SpringDataJpa

Spring Data JPA是較大的Spring Data系列的一部分，可輕鬆實現基於JPA的存儲庫。該模塊處理對基於JPA的數據訪問層的加強支持。它使構建使用數據訪問技術的Spring支持的應用程序變得更加容易。

實現應用程序的數據訪問層已經很長一段時間了。爲了執行簡單查詢以及執行分頁和審覈，必須編寫太多樣板代碼。Spring Data JPA旨在經過將工做量減小到實際須要的數量來顯着改善數據訪問層的實現。做爲開發人員，您將編寫包括自定義finder方法在內的存儲庫接口，Spring會自動提供實現。

使用EntityManager 來建立原生查詢語句

在service層的代碼:

@PersistenceContext
    EntityManager entityManager;

 @Override
 public Object findMeetingSignRecoredPage(Long meetingId, Integer pageIndex, Integer pageSize) {

        MeenoAssert.notNull(meetingId, ErrEnum.MEETING_ID_IS_EMPTY);
        Meeting meeting = this.meetingRepository.getOne(meetingId);
        MeenoAssert.notNull(meeting,ErrEnum.MEETING_IS_NOT_EXIST);

        Pageable pageable = PageUtils.getPageable(pageIndex,pageSize);

        StringBuilder sql = new StringBuilder();
        sql.append(" select ep.name,MAX(r.sign) from mnt_emp_rel_meeting as e ");
        sql.append(" left join mnt_sign_record as r on(r.employee_id=e.employee_id) ");
        sql.append(" left join mnt_employee as ep on(ep.id = e.employee_id) ");
        sql.append(" where e.meeting_id = ? ");
        sql.append(" order by r.sign desc,r.create_date asc ");


        Query query = entityManager.createNativeQuery(sql.toString());

        query.setFirstResult(pageable.getOffset());
        query.setMaxResults(pageable.getPageSize());
        query.setParameter(1,meetingId);

        List<Object[]> list = query.getResultList();
        List<SignRecordView> listView = Lists.newArrayList();

        if(list != null && !list.isEmpty()){
            for (Object[] objects : list) {
                String empName = objects[0]==null?null:objects[0].toString();
                Integer sign = objects[1]==null?Constants.SIGN_RECORD_NO:Integer.parseInt(objects[1].toString());
                SignRecordView view = new SignRecordView();
                view.setEmployeeName(empName);
                view.setSign(sign);
                listView.add(view);
            }
        }

        //count
        StringBuilder countSql = new StringBuilder();
        countSql.append(" select count(distinct e.id) from mnt_emp_rel_meeting as e ");
        countSql.append(" left join mnt_sign_record as r on(r.employee_id=e.employee_id) ");
        countSql.append(" left join mnt_employee as ep on(ep.id = e.employee_id) ");
        countSql.append(" where e.meeting_id = ? ");
        countSql.append(" order by r.sign desc,r.create_date asc ");

        Query countQuery = entityManager.createNativeQuery(countSql.toString());
        countQuery.setParameter(1,meetingId);
        Object singleResult = countQuery.getResultList().get(0);
        Integer count = singleResult==null?0:Integer.valueOf(singleResult.toString());


        Map<String, Object> resultPage = PageUtils.getResultPage(count, listView);

        return resultPage;
    }

PageUtils工具類代碼以下:

package com.meeno.framework.page.utils;

import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import lombok.Data;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

/** * @description: 分頁工具類 * @author: Wzq * @create: 2019-12-26 20:19 */
@Data
public class PageUtils {



    /** *@Description 獲取集合分頁對象 *@Param [list, pageIndex, pageSize] *@Return void *@Author Wzq *@Date 2020/1/6 *@Time 14:07 */
    public static  <T> Map<String,Object> getCollectionPage(List<T> list, Pageable pageable){
        if(list==null||list.isEmpty()){
            return PageUtils.getResultPage(0,null );
        }

        int offset = pageable.getOffset();
        int pageSize = pageable.getPageSize();

        List<T> listView = Lists.newArrayList();

        if(list!=null && !list.isEmpty()){
            if(list.size() < offset){
                return PageUtils.getResultPage(0,null );
            }
            for(;list.size() > offset && pageSize != 0 ; offset++,pageSize--){
                listView.add(list.get(offset));
            }
            return PageUtils.getResultPage(list.size(),listView);
        }
        return PageUtils.getResultPage(0,null );
    }




    /** *@Description 根據pageIndex和pageSize獲取Pageable *@Param [pageIndex, pageSize] *@Return org.springframework.data.domain.Pageable *@Author Wzq *@Date 2019/12/27 *@Time 11:12 */
    public static Pageable getPageable(Integer pageIndex, Integer pageSize){
        if(pageIndex==null){
            pageIndex = 0;
        }else{
            pageIndex--;
        }
        if(pageSize==null){
            pageSize = 10;
        }
        PageRequest pageRequest = new PageRequest(pageIndex, pageSize);
        return pageRequest;
    }

    /** *@Description 獲取分頁返回對象 *@Param [totalCount, list] *@Return java.util.Map<java.lang.String,java.lang.Object> *@Author Wzq *@Date 2019/12/26 *@Time 20:22 */
    public  static  Map<String,Object> getResultPage(Page<?> page, List<?> list){
        Map<String,Object> resultPageMap = Maps.newHashMap();
        resultPageMap.put("totalCount",page.getTotalElements());
        resultPageMap.put("list",list);
        return resultPageMap;
    }

    public  static  Map<String,Object> getResultPage(Integer count, List<?> list){
        Map<String,Object> resultPageMap = Maps.newHashMap();
        resultPageMap.put("totalCount",count);
        resultPageMap.put("list",list);
        return resultPageMap;
    }


}

我的微信公衆，常常更新一些實用的乾貨: