【Java】【33】分页处理

前言：

数据量太大时，前端就需要做翻页显示了，即点击第几页就拉取第几页的数据

正文：

1，在xml中写查询语句

Service层

注：用了rowBounds其实就是假分页了，会把数据查到内存里来，再去对应的数据集合给到前端。真分页的话，数据库查询XML里Oracle和MySQL写法不同，要注意

@Autowired TheDao theDao;  public PageModel<UserVo> getClerkListByBlur(QueryVo query) {     RowBounds rowBounds = new RowBounds((query.getPage() - 1) * query.getRows(), query.getRows());     int total = this.theDao.getCount(query);      PageModel<UserVo> pageModel = new PageModel<UserVo>();     pageModel.setPageNo(query.getPage());     pageModel.setPageSize(query.getRows());     pageModel.setTotalRecords(total);      List<UserVo> list = this.theDao.getList(query, rowBounds); //rowBounds     pageModel.setList(list);      return pageModel; }

Dao层

int getCount(QueryVo info);  List<UserVo> getList(QueryVo info, RowBounds rowBounds);

数据库查询XML

<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" > <mapper namespace="com.bf.dnh.dao.ClerkDao" >     <resultMap id="UserVoMap" type="com.bf.xx.params.base.UserVo" >         <id column="Id" property="id" jdbcType="VARCHAR" />              <result column="Name" property="name" jdbcType="VARCHAR" />         <result column="Province" property="province" jdbcType="VARCHAR" />         <result column="City" property="city" jdbcType="VARCHAR" />         <result column="Gender" property="gender" jdbcType="SMALLINT" />         <result column="Create_Time" property="createTime" jdbcType="TIMESTAMP" />     </resultMap>      <select id="getCount" resultType="int">         select count(1) from (           <include refid="sql_getList" />         ) T     </select>      <select id="getList" resultMap="UserVoMap">         <include refid="sql_getList" />         ORDER BY T.CREATE_TIME DESC     </select>      -- mysql 真分页写法     <select id="getTestList" resultMap="UserVoMap">         SELECT T.*          FROM USER T         ORDER BY T.NAME DESC         <if test="page != 0">             LIMIT #{start}, #{rows}         </if>     </select>      <sql id="sql_getList">         SELECT T.*           FROM USER T          WHERE T.STATUS = 1         <if test="keyword != null and keyword != ''">            AND T.NAME LIKE '%${keyword}%'         </if>     </sql>  </mapper>

2，mybatis的映射查询

Service层

@Autowired TheMapper theMapper;  public PageModel<UserVo> getClerkListByBlur(QueryVo query) {     Example example = new Example(QueryVo.class);     example.createCriteria()         .andEqualTo("status", 1)         .andLike("name", query.getKeyword());      PageModel<UserVo> pageModel = new PageModel<UserVo>();     pageModel.setPageNo(query.getPage());     pageModel.setPageSize(query.getRows());      int total = this.theMapper.selectCountByExample(query);     pageModel.setTotalRecords(total);      RowBounds rowBounds = new RowBounds((query.getPage() - 1) * query.getRows(), query.getRows());     List<UserVo> list = this.theMapper.selectByExampleAndRowBounds(example, rowBounds);     pageModel.setList(list);      return pageModel; }

Dao层

import com.bf.base.entity.QueryVo; import org.springframework.stereotype.Repository; import tk.mybatis.mapper.common.Mapper;  @Repository public interface TheMapper extends Mapper<QueryVo> { }

3，基础类

QueryVo类

public class QueryVo {     private int page; //页数      private int rows; //每页显示条数      private String keyword;      public int getPage() {         return page;     }      public void setPage(int page) {         this.page = page;     }      public int getRows() {         return rows;     }      public void setRows(int rows) {         this.rows = rows;     }      public String getKeyword() {         return keyword;     }      public void setKeyword(String keyword) {         this.keyword = keyword;     } }

-- 真分页的话，需要增加一个参数start，开始条数

private int start; //由page*rows计算得来  public int getStart() {     start = (page - 1) * rows;     return start; }  public void setStart(int start) {     this.start = start; }

PageModel类

package com.bf.base.params;  import java.util.List;  /**  * 封装分页信息  *  */ public class PageModel<E> {      //结果集     private List<E> list;      //查询记录数     private int totalRecords;      //每页多少条数据     private int pageSize;      //第几页     private int pageNo;      @Override     public String toString() {         return "PageModel [list=" + list + ", totalRecords=" + totalRecords + ", pageSize=" + pageSize + ", pageNo="                 + pageNo + "]";     }      /**      * 总页数      * @return      */     public int getTotalPages() {         return (totalRecords + pageSize - 1) / pageSize;     }      /**      * 取得首页      * @return      */     public int getTopPageNo() {         return 1;     }      /**      * 上一页      * @return      */     public int getPreviousPageNo() {         if (pageNo <= 1) {             return 1;         }         return pageNo - 1;     }      /**      * 下一页      * @return      */     public int getNextPageNo() {         if (pageNo >= getBottomPageNo()) {             return getBottomPageNo();         }         return pageNo + 1;     }      /**      * 取得尾页      * @return      */     public int getBottomPageNo() {         return getTotalPages();     }      public List<E> getList() {         return list;     }      public void setList(List<E> list) {         this.list = list;     }      public int getTotalRecords() {         return totalRecords;     }      public void setTotalRecords(int totalRecords) {         this.totalRecords = totalRecords;     }      public int getPageSize() {         return pageSize;     }      public void setPageSize(int pageSize) {         this.pageSize = pageSize;     }      public int getPageNo() {         return pageNo;     }      public void setPageNo(int pageNo) {         this.pageNo = pageNo;     } }