EasyExcel 写Excel超过限制自动切换sheet

EasyExcel 写Excel超过限制自动切换sheet

查询数据库超多表超百W数据量写Excel，这里有一个小常识，Excel 2007后版本，单个工作表的记录条数最多为1048576行，最大列数为16384列。如果多于单个sheet后自动切换新sheet

步骤描述

1. 查数据：查询待写入Excel的数据，并将待写的数据放在一个List对象中
2. 实例化sheet：判断总记录数，超过单sheet最大限制1048576行，计算sheet个数，否则写在一个sheet中
3. 写Excel： EasyExcel.write方法写数据到Excel中
4. 关闭： 写完后调用写相关操作 excelWriter.finsh

参考代码信息

1. 写入Excel中的对象

package com.test.zhanglu
import com.alibaba.excel.annotation.ExcelProperty;
import com.alibaba.excel.annotation.write.style.ColumnWidth;
import com.alibaba.excel.annotation.write.style.HeadRowHeight;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
@ColumnWidth(30)
@HeadRowHeight(30)
public class ExcelBean {
    @ExcelProperty("测点类型")
    private String deviceNameStr;
    @ExcelProperty("测点编码")
    private String deviceNo;
    @ExcelProperty("实时值")
    private double value;
    @ExcelProperty("安装地址")
    private String deviceAddr;
    @ExcelProperty("实时时间")
    private String realTime;

2 Excel 写入方法逻辑

package com.test.zhanglu

import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.ExcelWriter;
import com.alibaba.excel.util.DateUtils;
import com.alibaba.excel.write.metadata.WriteSheet;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.query.Criteria;
import org.springframework.data.mongodb.core.query.Query;
import org.springframework.test.context.junit4.SpringRunner;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;

import java.util.List;

@SpringBootTest
@RunWith(SpringRunner.class)
public class WriteExcelTest {
    @Autowired
    private MongoTemplate mongoTemplate;

    @Test
    public void getList() {
        String path = "D:\\001document\\04\\01\\09\\数据样本集\\" + "data_" + DateUtils.format(new Date(), "yyyyMMdd") + ".xlsx";
        //单表最多存储数
        int sheetMaxNum = 1048576;
        //跑去表头，单页数据最大行数为限制减一条
        int pageSize = 1048575;
        //获取查询的数据库表名
        List<String> tableNames = getTableName(2023, 11);
        //创建ExceWriter对象
        ExcelWriter excelWriter = EasyExcel.write(path).build();
        //所有查询出来的数据放在一个对象中
        List<ExcelBean> result = new ArrayList<>(10000000);
        for (String tableName : tableNames) {
            List<ExcelBean> list = new ArrayList<>();
            boolean isExists = mongoTemplate.collectionExists(tableName);
            if (!isExists) {
                continue;
            }
            Query query = new Query();
            //mongoTemplate 模糊查询
            query.addCriteria(Criteria.where("deviceAddr").regex("zhanglu"));
            query.addCriteria(Criteria.where("deviceNo").regex("A"));
            query.fields().include("deviceNo").include("deviceNameStr").include("deviceAddr").include("realTime").include("value").exclude("_id");

            list = mongoTemplate.find(query, ExcelBean.class, tableName);
            System.out.println(tableName + ":" + list.size());
            result.addAll(list);

        }
        int sheetCount = 0;
        int total = result.size();
        System.out.println("===数据总量==" + total);
        //根据总数计算需要多少个sheet页
        if (total > sheetMaxNum) {
            sheetCount = total % pageSize == 0 ? total / pageSize : (total / pageSize) + 1;
        } else {
            sheetCount = 1;
        }
        int currentIndex = 0;
        //按sheet页写数据
        for (int num = 1; num <= sheetCount; num++) {
            String stName = "测试数据-" + num;
            //实例化sheet对象，写个sheetNo,sheetName。这里敲黑板，需要写sheetNo，不然只有一个sheet没切换
            WriteSheet writeSheet = EasyExcel.writerSheet(num,stName).head(ExcelBean.class).build();
            System.out.println(stName);
            //计算当前sheet从第几条记录开始写。和分页是一个道理
            int fromIndex = pageSize * num;
            if (fromIndex >= total) {
                fromIndex = total;
            }
            //调用写的方法
            excelWriter.write(result.subList(currentIndex, fromIndex), writeSheet);
            //赋值给下一个sheet页的开始索引
            currentIndex = fromIndex;
        }
        //关闭写操作
        excelWriter.finish();

    }


  /**以下是查询表名的方法，查询多个数据表，表名规则是日期为后缀**/
  
   public static List<String> getTableName(int year, int month) {
        List<String> dates = new ArrayList<>();

        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month - 1, 1); // 设置为当前月的第一天

        int maxDay = calendar.getActualMaximum(Calendar.DAY_OF_MONTH); // 获取当前月的最大天数

        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMdd");
        for (int i = 1; i <= maxDay; i++) {
            calendar.set(Calendar.DAY_OF_MONTH, i);
            String date = dateFormat.format(calendar.getTime());
            String talbeName = "zhanglu.test_" + date + "_his_value";
            dates.add(talbeName);
        }

        return dates;
    }

知识小总结

1. sheet没切换，每次都写一个sheet中，超限报错

原因： WriteSheet writeSheet = EasyExcel.writerSheet(num,stName).head(ExcelBean.class).build();
这行代码中 EasyExcel.writerSheet(num,stName).只给了一个sheetName参数，没给sheetNo。 如下所示：EasyExcel.writerSheet(stName)

2. Bean中常用注解说明

可参考官网：
https://easyexcel.opensource.alibaba.com/docs/current/api/write#%E6%B3%A8%E8%A7%A3