1、流式查询
1、实体类
package com.wanqi.pojo;import java.util.Date;/** * @Description TODO * @Version 1.0.0 * @Date 2022/9/12 * @Author wandaren */public class VoteRecord { private int id; private String userId; private int voteNum; private int groupId; private boolean status; private Date createTime; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getUserId() { return userId; } public void setUserId(String userId) { this.userId = userId; } public int getVoteNum() { return voteNum; } public void setVoteNum(int voteNum) { this.voteNum = voteNum; } public int getGroupId() { return groupId; } public void setGroupId(int groupId) { this.groupId = groupId; } public boolean isStatus() { return status; } public void setStatus(boolean status) { this.status = status; } public Date getCreateTime() { return createTime; } public void setCreateTime(Date createTime) { this.createTime = createTime; } @Override public String toString() { return "VoteRecord{" + "id=" + id + ", userId='" + userId + '\'' + ", voteNum=" + voteNum + ", groupId=" + groupId + ", status=" + status + ", createTime=" + createTime + '}'; }}2、mapper
package com.wanqi.mapper;import com.wanqi.pojo.VoteRecord;import org.apache.ibatis.annotations.Mapper;import org.apache.ibatis.annotations.Options;import org.apache.ibatis.annotations.ResultType;import org.apache.ibatis.annotations.Select;import org.apache.ibatis.cursor.Cursor;import org.apache.ibatis.mapping.ResultSetType;import org.apache.ibatis.session.ResultHandler;import java.util.List;/** * @Description TODO * @Version 1.0.0 * @Date 2022/9/12 * @Author wandaren */@Mapperpublic interface VoteRecordMapper {// @Select("select id, user_id as userId, vote_num as voteNum, group_id as groupId, status, create_time as createTime from vote_record")// @Options(resultSetType = ResultSetType.FORWARD_ONLY, fetchSize = Integer.MIN_VALUE)// @ResultType(VoteRecord.class) void all(ResultHandler resultHandler);}3、mapper配置
select id, user_id as userId, vote_num as voteNum, group_id as groupId, status, create_time as createTime from vote_record 
:::info
this.query.getResultType() == Type.FORWARD_ONLY
this.query.getResultFetchSize() == Integer.MIN_VALUE�
:::
- fetchSize必须设置成-2147483648
4、自定义处理结果集
package com.wanqi.handler;import com.wanqi.pojo.VoteRecord;import org.apache.ibatis.session.ResultContext;import org.apache.ibatis.session.ResultHandler;import org.springframework.util.ObjectUtils;import java.util.ArrayList;import java.util.List;/** * @Description TODO * @Version 1.0.0 * @Date 2022/9/12 * @Author wandaren */public class VoteRecordHandler implements ResultHandler { // 这是每批处理的大小 private final static int BATCH_SIZE = 1000; private int size; private final List list = new ArrayList(); @Override public void handleResult(ResultContext resultContext) { VoteRecord voteRecord = resultContext.getResultObject(); list.add(voteRecord); size++; if (size == BATCH_SIZE) { handle(); } } private void handle() { try { if (ObjectUtils.isEmpty(list)) { return; } // 在这里可以对你获取到的批量结果数据进行需要的业务处理// list.parallelStream().forEach(s -> System.out.println(s.getId())); } finally { // 处理完每批数据后后将临时清空 size = 0; list.clear(); } } // 这个方法给外面调用，用来完成最后一批数据处理 public void end(){ handle();// 处理最后一批不到BATCH_SIZE的数据 }}5、service层
package com.wanqi.service;import com.github.pagehelper.PageHelper;import com.wanqi.handler.VoteRecordHandler;import com.wanqi.mapper.VoteRecordMapper;import com.wanqi.pojo.VoteRecord;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import java.util.List;/** * @Description TODO * @Version 1.0.0 * @Date 2022/9/12 * @Author wandaren */@Servicepublic class VoteRecordService { @Autowired private VoteRecordMapper voteRecordMapper; public String allVoteRecord(){ VoteRecordHandler voteRecordHandler = new VoteRecordHandler(); voteRecordMapper.all(voteRecordHandler); System.out.println("--------------------------------------------------------"); voteRecordHandler.end(); return "处理结束！！！"; }}2、分页插件1、引入依赖
com.github.pagehelperpagehelper-spring-boot-starter1.4.32、配置文件
spring: redis: host: 172.16.156.139 password: qifeng database: 2 port: 6379 datasource: type: com.alibaba.druid.pool.DruidDataSource url: jdbc:mysql://172.16.156.139:3306/test?allowPublicKeyRetrieval=true username: wq password: qifeng driver-class-name: com.mysql.cj.jdbc.Drivermybatis: type-aliases-package: com.wanqi.pojo mapper-locations: classpath:mapper/*.xml#分页插件的配置pagehelper: #配置四項 hprs helper-dialect: mysql #分页助手方言：mysql params: count=countSql #为了支持 startPage(Object params) 方法 support-methods-arguments: true #支持通过 Mapper 接口参数来传递分页参数，默认值 false reasonable: true #分页合理化参数，默认值为 false,页码不为负，不超总页码3、mapper接口
package com.wanqi.mapper;import com.wanqi.pojo.VoteRecord;import org.apache.ibatis.annotations.Mapper;import org.apache.ibatis.session.ResultHandler;import java.util.List;/** * @Description TODO * @Version 1.0.0 * @Date 2022/9/12 * @Author wandaren */@Mapperpublic interface VoteRecordMapper { List one();}4、mapper配置
select id, user_id as userId, vote_num as voteNum, group_id as groupId, status, create_time as createTime from vote_record 5、servlce层
package com.wanqi.service;import com.github.pagehelper.PageHelper;import com.wanqi.handler.VoteRecordHandler;import com.wanqi.mapper.VoteRecordMapper;import com.wanqi.pojo.VoteRecord;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;import java.util.List;/** * @Description TODO * @Version 1.0.0 * @Date 2022/9/12 * @Author wandaren */@Servicepublic class VoteRecordService { @Autowired private VoteRecordMapper voteRecordMapper; public void one(){ PageHelper.startPage(1, 50000); List list = voteRecordMapper.one(); PageInfo pageInfo = new PageInfo(list); System.out.println("getTotal: "+pageInfo.getTotal()); System.out.println("getPages: "+pageInfo.getPages()); System.out.println("getPageNum: "+pageInfo.getPageNum()); System.out.println("getPageSize: "+pageInfo.getPageSize()); System.out.println("getEndRow: "+pageInfo.getEndRow()); }}