ArrayList/MySQL数据批量写入Excel表格

ArrayList/MySQL数据集合写入Excel 1.文章概述： 　　写入 Excel 文件通常需要使用一些库或工具，而"EasyExcel"通常是指的阿里巴巴开源的EasyExcel库。这个库可以让我们在Java中简便地进行Excel文件的读写操作。 2.导入配置：

 <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>easyexcel</artifactId>
            <version>3.2.0</version>
</dependency>
 <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.2</version>
</dependency>

3.Excel模板类

package com.ccc.bean.tools_enty;

import com.alibaba.excel.annotation.ExcelProperty;
import lombok.Data;
import lombok.NoArgsConstructor;


@NoArgsConstructor
@Data
public class WriteDataBean  implements Comparable {
　　 // Excel标头名称
    @ExcelProperty("a")
    private String a;
    @ExcelProperty("b")
    private String b;

    public String getA() {
        return a;
    }

    public void setA(String a) {
        this.a = a;
    }

    public String getB() {
        return b;
    }

    public void setB(String b) {
        this.b = b;
    }

    @Override
    public int compareTo(Object o) {
//        //可设置排序
//        if (o instance of WriteDataBean){ 
              // WechatOfficialAccountBean wechatOfficialAccountBean= (WechatOfficialAccountBean) o; 
              // return this.getUpload_time().hashCode()-wechatOfficialAccountBean.getUpload_time().hashCode(); 
       // } 
        throw new ClassCastException("不能转换 WriteDataBean ");

 } 
}

4.工具类示例代码：

package com.ccc.tools;

import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.ExcelWriter;
import com.alibaba.excel.write.metadata.WriteSheet;
import com.felephantst.bean.tools_enty.WriteDataBean;

import java.io.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @ClassName: FileTool
 * @Description TODO 操作文件工具类
 * @Author: 东霖
 * @Date: 2023/9/12 13:19
 * @Version 1.0
 **/
public class FileTool {

    /**
     * 读取指定文件
     *
     * @param filePath
     * @return 返回一个字符串集合
     */
    public static List<String> readFile(String filePath) {
        List<String> stringList = new ArrayList<>();
        try {
            FileReader fr = new FileReader(filePath);
            BufferedReader bf = new BufferedReader(fr);
            String str;
            // 按行读取字符串
            while ((str = bf.readLine()) != null) {
                stringList.add(str);
            }
            bf.close();
            fr.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return stringList;
    }

    /**
     * TODO： 小数据量写出数据到 Excel（2000条左右用这个）
     *
     * @param bean        模板类
     * @param outFilePath 输出路径全称：test.xlsx
     * @param sheetName   excel Sheet 名称
     * @param collect     数据集
     */
    public static void writeMinDataExcel(Class<?> bean, String outFilePath, String sheetName, ArrayList collect) {
        OutputStream outputStream = null;
        try {
            outputStream = new FileOutputStream(outFilePath);
            EasyExcel.write(outputStream, bean).sheet(sheetName).doWrite(collect);
            //写出到文件
            outputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * TODO： 大数据量写出数据到 Excel（2000条左右用这个）
     *
     * @param bean        模板类
     * @param outFilePath 输出路径全称：test.xlsx
     * @param sheetName   excel Sheet 名称
     * @param sizeLimitDataList     数据集
     * @param sizeLimit   设置多少条数据为一个Sheet
     */
    public static void writeMaxDataExcel(Class<?> bean, String outFilePath, String sheetName, ArrayList sizeLimitDataList, Integer sizeLimit) {
        // 总Sheet数
        int num = sizeLimitDataList.size() / sizeLimit + (sizeLimitDataList.size() % sizeLimit > 0 ? 1 : 0);
        // 输出流
        OutputStream outputStream = null;
        try {
            // 以字节流的形式输出响应正文
            outputStream = new FileOutputStream(outFilePath);
            try (ExcelWriter excelWriter = EasyExcel.write(outputStream, bean).build()) {
                // 中间list调用写入
                List<?> partList = null;
                WriteSheet writeSheet =null;
                for (int i = 0; i < num; i++) {
                    // 每次写入都要创建WriteSheet, 这里注意必须指定sheetNo, 并且sheetName必须不一样
                    writeSheet = EasyExcel.writerSheet(i, sheetName + (i + 1)).build();
                    // 截取批次长度的list
                    partList = sizeLimitDataList.subList(0, sizeLimit);
                    // 分批业务逻辑处理- 打印替代
                    excelWriter.write(partList, writeSheet);
                    // 去除已经处理的部分 (Arrays.asList()方式生成的数据不能进行此修改操作，会报错)
                    partList.clear();
                }
                // 获取最后一次截取后的剩余列表数据
                if (!sizeLimitDataList.isEmpty()) {
                    // 业务逻辑数据处理
                    excelWriter.write(sizeLimitDataList, writeSheet);
                }
            }
            } catch (IOException ex) {
                throw new RuntimeException(ex);
            } finally {
                if (outputStream != null) {
                    try {
                        outputStream.close();
                    } catch (IOException ex) {
                        throw new RuntimeException(ex);
                    }
                }
            }
        }

        public static void main (String[]args){
        WriteDataBean writeDataBean = new WriteDataBean();
        writeDataBean.setA("a");
        writeDataBean.setB("b");
        WriteDataBean writeDataBean1 = new WriteDataBean();
        writeDataBean1.setA("ad");
        writeDataBean1.setB("bd");
        objects.add(writeDataBean1);
        objects.add(writeDataBean);

        writeMaxDataExcel(WriteDataBean.class, "D://cdc.xlsx", "test", objects, 1);
        writeMinDataExcel(WriteDataBean.class, "D://cddc.xlsx", "test", objects);
    
    }
}