page 分页工具

package utils;

import java.io.Serializable;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * @author 类此够
 * @Description 分页工具类，贼好用的分页工具类
 */
public class PageUtils implements Serializable {
    public static void main(String[] args) {
//        PageUtils p = new PageUtils();
//        p.setPageIndex(1); // 当前页
//        // p.setStart(0); // 起始条数
//        p.setLimit(10); // 每页条数
//        p.setParam("name", "xiaohei");
//        /*
//         * 只需要根据param查询总条数设置一下, 其他字段:例如共多少页,是否有下一页,是否有上一页,当前页多少条,字段自动会根据totalCount算出;
//         */
//        p.setTotalCount(20);
//
//        p.clearParam();
//        System.out.println(JSON.toJSONString(p));
    }

    private static final long   serialVersionUID = 1L;

    private int                 pageIndex;                                       // 当前页
    private int                 start;                                           // 起始条数
    private int                 limit;                                           // 每页显示条数
    private int                 totalCount;                                      // 总条数

    // 以下参数只能算, 不能有setXX方法---start
    // 根据param参数查询出totalCount, 计算设置
    private int                 totalPage;                                       // 总页数
    private int                 totalCountPageIndex;                             // 当前页有多少条
    private boolean             hasNextPage;                                     // 是否有下一夜
    private boolean             hasLastPage;                                     // 是否有上一夜
    // 以下参数只能算, 不能有setXX方法---end

    private String              sortName;                                        // 排序字段
    private String              sortOrder;                                       // 排序方式:(ASC/DESC)
    private Map<String, Object> queryParam       = new HashMap<String, Object>();
    private List<?>             data;

    public Map<String, Object> getParam() {
        // 校验部分参数合理性
        if ((this.start < 0) || (this.pageIndex <= 0) || (this.limit <= 0)) {// 参数错误, (为最首页准备)
            throw new RuntimeException("请检查入参 start / pageIndex / limit !");
        }
        
        // 如果既有start且start>0, 又有pageIndex, 则优先取start, 且不再做分页处理(已传start, 则本意就是指定查多少条)
        if (this.start == 0) {
            this.start = (this.pageIndex - 1) * this.limit;
        } else {
            queryParam.put("pageIndex", "-999"); // 已传start>0
        }
        
        queryParam.put("start", this.start);
        queryParam.put("limit", this.limit);
        queryParam.put("sortName", this.sortName);
        queryParam.put("sortOrder", this.sortOrder);
        return queryParam;
    }

    public int getTotalCount() {
        return totalCount;
    }

    /**
     * @author 类此够
     * @param
     * @return 
     * @description 
     * 设置总条数, 同时计算是否有上下页
     */
    public void setTotalCount(int totalCount) {
        if (totalCount == 0) {
            return;
        }

        if ((totalCount > 0) && (this.start >= totalCount)) {
            System.out.println("start: " + start + ", pageIndex: " + pageIndex + ", limit: " + limit + ", totalCount: " + totalCount);
            throw new RuntimeException("请检查入参!");
        }
        this.totalCount = totalCount;
        // 参数 有start且start>0, 则优先取start, 且不再做分页处理
        if ("-999".equals(queryParam.get("pageIndex"))) {
            queryParam.remove("pageIndex");
            return;
        }
        if (totalCount <= this.limit) { // 首页即总页
            this.pageIndex = 1;
            this.totalCountPageIndex = totalCount;
            return;
        }
        // 总页数
        this.totalPage = (totalCount % this.limit == 0) ? (totalCount / this.limit) : (totalCount / this.limit + 1);
        /* 根据起始条数,算出当前页; */
        this.pageIndex = (this.start == 0) ? pageIndex : (start / limit + 1);

        if (pageIndex == 1) {// 首页
            this.totalCountPageIndex = limit;
            this.hasNextPage = true;
        } else if ((pageIndex > 1) && (pageIndex == totalPage)) { // 末页
            this.totalCountPageIndex = (totalCount - (pageIndex - 1) * limit);
            this.hasLastPage = true;
        } else {// 中间页
            this.totalCountPageIndex = limit;
            this.hasLastPage = true;
            this.hasNextPage = true;
        }
    }

    public void setParam(Map<String, Object> param) {
        queryParam.putAll(param);
    }

    public void setParam(String key, Object value) {
        queryParam.put(key, value);
    }

    public void setParam(String key, String value) {
        queryParam.put(key, value);
    }

    public void removeParam(String key) {
        queryParam.remove(key);
    }

    public void clearParam() {
        queryParam.clear();
        sortName = null;
        sortOrder = null;
    }

    public PageUtils() {
        // 不设置页数和条数的话;默认显示第一页,每页10条数据,
        this.start = 0;
        this.pageIndex = 1;
        this.limit = 10;
    }

    public PageUtils(int pageIndex, int limit) {
        this.pageIndex = pageIndex;
        this.limit = limit;
    }

    public String getSortName() {
        return sortName;
    }

    public void setSortName(String sortName) {
        this.sortName = sortName;
    }

    public String getSortOrder() {
        return sortOrder;
    }

    public void setSortOrderASC() {
        this.sortOrder = "ASC";
    }

    public void setSortOrderDESC() {
        this.sortOrder = "DESC";
    }

    public List<?> getData() {
        return data;
    }

    public void setData(List<?> data) {
        this.data = data;
    }

    public int getPageIndex() {
        return pageIndex;
    }

    public void setPageIndex(int pageIndex) {
        this.pageIndex = pageIndex;
    }

    public int getLimit() {
        return limit;
    }

    public void setLimit(int limit) {
        this.limit = limit;
    }

    public int getTotalPage() {
        return totalPage;
    }

    public int getTotalCountPageIndex() {
        return totalCountPageIndex;
    }

    public void setStart(int start) {
        this.start = start;
    }

    public boolean getHasNextPage() {
        return hasNextPage;
    }

    public boolean getHasLastPage() {
        return hasLastPage;
    }
}

• dao层的Mapper文件方法:

• <?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.stu.dao.StuMapper">
      <resultMap id="BaseResultMap" type="com.stu.model.StuVo">
          <result column="id" jdbcType="INTEGER" property="id" />
          <result column="stu_id" jdbcType="VARCHAR" property="stuId" />
          <result column="name" jdbcType="VARCHAR" property="name" />
          <result column="sex" jdbcType="INTEGER" property="sex" />
          <result column="creat_time" jdbcType="TIMESTAMP" property="creatTime" />
          <result column="update_Time" jdbcType="VARCHAR" property="updateTime" />
          <result column="score" jdbcType="DECIMAL" property="score" />
      </resultMap>
  
      <insert id="insert" parameterType="com.stu.dto.StuDto">
          INSERT INTO stu
          <trim prefix="(" suffix=")" suffixOverrides=",">
              <if test="id != null">id,</if>
              <if test="stuId != null">stu_id,</if>
              <if test="name != null">name,</if>
              <if test="sex != null">sex,</if>
              <if test="creatTime != null">creat_time,</if>
              <if test="updateTime != null">update_Time,</if>
              <if test="score != null">score,</if>
          </trim>
          VALUES
          <trim prefix="(" suffix=")" suffixOverrides=",">
              <if test="id != null">#{id},</if>
              <if test="stuId != null">#{stuId},</if>
              <if test="name != null">#{name},</if>
              <if test="sex != null">#{sex},</if>
              <if test="creatTime != null">#{creatTime},</if>
              <if test="updateTime != null">#{updateTime},</if>
              <if test="score != null">#{score},</if>
          </trim>
      </insert>
  
      <delete id="deleteById">
          DELETE FROM stu WHERE
          id = #{id}
      </delete>
  
      <update id="update" parameterType="com.stu.dto.StuDto">
          UPDATE stu SET
          <trim prefixOverrides=",">
              <if test="stuId != null">,stu_id=#{stuId}</if>
              <if test="name != null">,name=#{name}</if>
              <if test="sex != null">,sex=#{sex}</if>
              <if test="creatTime != null">,creat_time=#{creatTime}</if>
              <if test="updateTime != null">,update_Time=#{updateTime}</if>
              <if test="score != null">,score=#{score}</if>
          </trim>
          WHERE id = #{id}
      </update>
  
      <select id="queryById" resultMap="BaseResultMap">
          SELECT
          id, stu_id, name, sex, creat_time, update_Time, score
          FROM stu
          WHERE id = #{id}
      </select>
  
      <select id="queryListCount" parameterType="java.util.Map" resultType="Integer">
          SELECT COUNT(1) FROM stu
          <include refid="Base_Where_Clause" />
      </select>
  
      <select id="queryList" parameterType="java.util.Map" resultMap="BaseResultMap">
          SELECT
          id, stu_id, name, sex, creat_time, update_Time, score
          FROM stu
          <include refid="Base_Where_Clause" />
          <if test="sortName != null and sortName !=''">
              ORDER BY ${sortName}
              <if test="sortOrder != null and sortOrder !=''">
                  ${sortOrder}
              </if>
          </if>
          <if test="start != null and limit != null and limit !=0">
              LIMIT #{start}, #{limit}
          </if>
      </select>
  
      <sql id="Base_Where_Clause">
          <where>
              <trim prefixOverrides="and">
                  <if test="id != null and id != ''"> AND id = #{id}</if>
                  <if test="stuId != null and stuId != ''"> AND stu_id = #{stuId}</if>
                  <if test="name != null and name != ''"> AND name = #{name}</if>
                  <if test="sex != null and sex != ''"> AND sex = #{sex}</if>
                  <if test="creatTime != null and creatTime != ''"> AND creat_time = #{creatTime}</if>
                  <if test="updateTime != null and updateTime != ''"> AND update_Time = #{updateTime}</if>
                  <if test="score != null and score != ''"> AND score = #{score}</if>
              </trim>
          </where>
      </sql>
  </mapper>

  • Dao接口

    package com.stu.dao;
    
    import java.util.List;
    import java.util.Map;
    
    import org.apache.ibatis.annotations.Param;
    
    import com.stu.dto.StuDto;
    import com.stu.model.StuVo;
    
    public interface StuMapper {
        // 插入
        int insert(StuDto dto);
    
        // 删除
        int deleteById(@Param("id") String id);
    
        // 更新
        int update(StuDto dto);
    
        // 查询单条
        StuVo queryById(@Param("id") String id);
    
        // 查询条数
        int queryListCount(Map<String, Object> param);
    
        // 查询集合
        List<StuVo> queryList(Map<String, Object> param);
    }

    • 实体类（入参/反参）对象

    • package com.stu.model;
      
      import java.io.Serializable;
      import java.sql.Timestamp;
      
      public class StuVo implements Serializable {
          private static final long    serialVersionUID    = 1L;
      
          private String                id;                            // 
          private String                stuId;                        // 学生号
          private String                name;                        // 姓名
          private String                sex;                        // 性别(1男,2女)
          private Timestamp            creatTime;                    // 创建时间
          private String                updateTime;                    // 修改时间
          private Long                score;                        // 
      
          public void setId(String id) {
              this.id = id;
          }
      
          public String getId() {
              return id;
          }
      
          public void setStuId(String stuId) {
              this.stuId = stuId;
          }
      
          public String getStuId() {
              return stuId;
          }
      
          public void setName(String name) {
              this.name = name;
          }
      
          public String getName() {
              return name;
          }
      
          public void setSex(String sex) {
              this.sex = sex;
          }
      
          public String getSex() {
              return sex;
          }
      
          public void setCreatTime(Timestamp creatTime) {
              this.creatTime = creatTime;
          }
      
          public Timestamp getCreatTime() {
              return creatTime;
          }
      
          public void setUpdateTime(String updateTime) {
              this.updateTime = updateTime;
          }
      
          public String getUpdateTime() {
              return updateTime;
          }
      
          public void setScore(Long score) {
              this.score = score;
          }
      
          public Long getScore() {
              return score;
          }
      
      }

      package com.stu.dto;
      
      import java.io.Serializable;
      
      public class StuDto implements Serializable {
          private static final long    serialVersionUID    = 1L;
      
          private String                id;                            // 
          private String                stuId;                        // 学生号
          private String                name;                        // 姓名
          private String                sex;                        // 性别(1男,2女)
          private String                creatTime;                    // 创建时间
          private String                updateTime;                    // 修改时间
          private String                score;                        // 
      
          public void setId(String id) {
              this.id = id;
          }
      
          public String getId() {
              return id;
          }
      
          public void setStuId(String stuId) {
              this.stuId = stuId;
          }
      
          public String getStuId() {
              return stuId;
          }
      
          public void setName(String name) {
              this.name = name;
          }
      
          public String getName() {
              return name;
          }
      
          public void setSex(String sex) {
              this.sex = sex;
          }
      
          public String getSex() {
              return sex;
          }
      
          public void setCreatTime(String creatTime) {
              this.creatTime = creatTime;
          }
      
          public String getCreatTime() {
              return creatTime;
          }
      
          public void setUpdateTime(String updateTime) {
              this.updateTime = updateTime;
          }
      
          public String getUpdateTime() {
              return updateTime;
          }
      
          public void setScore(String score) {
              this.score = score;
          }
      
          public String getScore() {
              return score;
          }
      
      }

      package zweb.service;
      
      import java.util.List;
      import java.util.Map;
      
      import org.springframework.beans.factory.annotation.Autowired;
      import org.springframework.stereotype.Service;
      
      import com.stu.dao.StuMapper;
      import com.stu.model.StuVo;
      
      import utils.PageUtils;
      
      @Service
      public class StuService {
      
          @Autowired
          private StuMapper stuMapper;
      
          public PageUtils queryList(PageUtils p) {
              Map<String, Object> param = p.getParam();
              int total = stuMapper.queryListCount(param);
              if (total != 0) {
                  p.setTotalCount(total);
                  List<StuVo> dataList = stuMapper.queryList(param);
                  p.setData(dataList);
              }
              p.clearParam();
              return p;
          }
      }

          /**
           * @author 类此够
           * 获取列表
           */
          @ResponseBody
          @RequestMapping("/getStuList")
          public JSONObject getStuList(HttpServletRequest request, HttpServletResponse response) {
              JSONObject ret = new JSONObject();
              ret.put("success", true);
              ret.put("errorCode", 200);
              ret.put("errorMsg", "");
              PageUtils page = new PageUtils();
      
              try {
                  if (StringUtils.isNotEmpty(request.getParameter("pageIndex"))) {
                      page.setPageIndex(Integer.parseInt(request.getParameter("pageIndex")));
                  }
                  if (StringUtils.isNotEmpty(request.getParameter("limit"))) {
                      page.setLimit(Integer.parseInt(request.getParameter("limit")));
                  }
                  page = stuService.queryList(page);
                  ret.put("data", page);
              } catch (Exception e) {
                  ret.put("success", false);
                  ret.put("errorCode", 500);
                  ret.put("errorMsg", "服务器异常,请联系管理员!");
                  e.printStackTrace();
              } finally {
                  return ret;
              }
      
          }

      主要关注点：
      1。controller层的request入参
      2。service层调用dao时候先查条数，
      |----条数为0直接返回！！
      |----条数不为0，设置页数总条数（此时PageUtils会自动计算：是否有上/下一页、总页数、当前页条数等），并继续查询集合返回分页对象出去(注意清空查询参数)
      ————————————————
      版权声明：本文为CSDN博主「昵称同学」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
      原文链接：https://blog.csdn.net/qq_37001743/article/details/122000333