<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>easyexcel</artifactId>
    <version>3.1.5</version>
</dependency>
<dependency>
    <groupId>cn.hutool</groupId>
    <artifactId>hutool-all</artifactId>
    <version>5.8.4</version>
</dependency>

/**
 * @author wangzhenjun
 * @date 2023/7/4 17:09
 */
@Data
public class TestExcel {

    private String contractNo;

    private String address;
    
	private String dateTime;

    private List<Item> itemList;

    @Data
    public static class Item{

        private String name;

        private BigDecimal price;
    }
}

@SneakyThrows
@GetMapping("/excel")
public void excel (HttpServletResponse response){
    int size = 2;
    List<TestExcel> testExcels = new ArrayList<>();
    for (int i = 0; i < size; i++) {
        TestExcel testExcel = new TestExcel();
        testExcel.setContractNo("HT07040" + (i + 1));
        testExcel.setAddress("青島" + i + "號基地");
        testExcel.setDateTime("2023-07-05");
        testExcels.add(testExcel);
        List<TestExcel.Item> itemList = new ArrayList<>();
        for (int j = 0; j < size; j++) {
            TestExcel.Item item = new TestExcel.Item();
            item.setName("商品" + (j + 1));
            item.setPrice(new BigDecimal("188").multiply(new BigDecimal(j + 1)));
            itemList.add(item);
        }
        testExcel.setItemList(itemList);
    }
    response.setCharacterEncoding("utf-8");
    String fileName = URLEncoder.encode("測試", "UTF-8").replaceAll("\\+", "%20");
    response.setHeader("Content-disposition", "attachment;filename*=utf-8''" + fileName + ".xlsx");
    ClassPathResource classPathResource = new ClassPathResource("template" + File.separator + "測試.xlsx");
    InputStream stream = classPathResource.getStream();
    // 把excel流給這個(gè)對象，后續(xù)可以操作
    XSSFWorkbook workbook = new XSSFWorkbook(stream);
    // 設(shè)置模板的第一個(gè)sheet的名稱，名稱我們使用合同號
    workbook.setSheetName(0, testExcels.get(0).getContractNo());
    for (int i = 1; i < size; i++) {
        // 剩余的全部復(fù)制模板sheet0即可
        workbook.cloneSheet(0, testExcels.get(i).getContractNo());
    }
    // 把workbook寫到流里
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    workbook.write(baos);
    byte[] bytes = baos.toByteArray();
    stream = new ByteArrayInputStream(bytes);
    ExcelWriter excelWriter = EasyExcel.write(response.getOutputStream()).withTemplate(stream).build();

    for (TestExcel testExcel : testExcels) {
        WriteSheet writeSheet = EasyExcel.writerSheet(testExcel.getContractNo()).build();
        // list不是最后一行，下面還有數(shù)據(jù)需要填充 就必須設(shè)置 forceNewRow=true 但是這個(gè)就會(huì)把所有數(shù)據(jù)放到內(nèi)存 會(huì)很耗內(nèi)存
        FillConfig fillConfig = FillConfig.builder().forceNewRow(Boolean.TRUE).direction(WriteDirectionEnum.VERTICAL).build();
        excelWriter.fill(testExcel, writeSheet);
        excelWriter.fill(new FillWrapper("item", testExcel.getItemList()), fillConfig, writeSheet);
    }
    excelWriter.finish();
    baos.close();
    stream.close();
}