详解mybatis流式查询与分页插件

2022-11-21 14:10:30 作者：花开重日

这篇文章主要介绍了mybatis流式查询与分页插件,本文通过实例代码给大家讲解的非常详细，对大家的学习或工作具有一定的参考借鉴价值，需要的朋友可以参考下

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
 */
@Mapper
public 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<VoteRecord> resultHandler);
}

3、mapper配置

<?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.wanqi.mapper.VoteRecordMapper">

        <select id="all" resultType="com.wanqi.pojo.VoteRecord" resultSetType="FORWARD_ONLY"
                fetchSize="-2147483648">
            select id, user_id as userId, vote_num as voteNum, group_id as groupId, status, create_time as createTime
            from vote_record
        </select>

</mapper>

:::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<VoteRecord> {
    // 这是每批处理的大小
    private final static int BATCH_SIZE = 1000;
    private int size;
    private final List<VoteRecord> list = new ArrayList<>();

    @Override
    public void handleResult(ResultContext<? extends VoteRecord> 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
 */
@Service
public 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

<dependency>
			<groupId>com.github.pagehelper</groupId>
			<artifactId>pagehelper-spring-boot-starter</artifactId>
			<version>1.4.3</version>
		</dependency>

2、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.Driver
mybatis:
  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
 */
@Mapper
public interface VoteRecordMapper {
    List<VoteRecord> one();
}

4、mapper配置

<?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.wanqi.mapper.VoteRecordMapper">

  <select id="one" resultType="com.wanqi.pojo.VoteRecord">
        select id, user_id as userId, vote_num as voteNum, group_id as groupId, status, create_time as createTime
        from vote_record
    </select>

</mapper>

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
 */
@Service
public class VoteRecordService {

    @Autowired
    private VoteRecordMapper voteRecordMapper;

    public void one(){
        PageHelper.startPage(1, 50000);
        List<VoteRecord> list = voteRecordMapper.one();
        PageInfo<VoteRecord> 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());
    }
}

到此这篇关于mybatis流式查询与分页插件的文章就介绍到这了,更多相关mybatis分页插件内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！