<dependency>
    <groupId>cn.hutool</groupId>
    <artifactId>hutool-all</artifactId>
    <version>5.8.4.M1</version>
</dependency>

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>5.0.0</version>
</dependency>
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml-full</artifactId> 
    <version>5.0.0</version>
</dependency>

package io.supers.common.utils;

import cn.hutool.core.io.IoUtil;
import cn.hutool.core.util.URLUtil;
import cn.hutool.poi.excel.ExcelUtil;
import cn.hutool.poi.excel.ExcelWriter;
import cn.hutool.poi.excel.style.StyleUtil;
import io.supers.framework.em.BaseErrorEnum;
import io.supers.framework.exception.RRException;
import org.apache.commons.collections.CollectionUtils;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.DataFormat;
import org.apache.poi.ss.usermodel.HorizontalAlignment;
import org.apache.poi.ss.usermodel.Workbook;
import org.springframework.web.multipart.MultipartFile;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
import java.util.Map;

/**
 * Excel 工具類
 *
 * @author guoc
 * @date 2022年05月31日 下午 17:21
 */
public class ExcelUtils {

    /**
     * 下載 Excel 模板 (只有表頭的 Excel)
     *
     * @param response response
     * @param headers  表頭
     * @param fileName 文件名
     */
    public static void exportHeaders(HttpServletResponse response, List<String> headers, String fileName) {
        export(response, null, headers, fileName);
    }

    /**
     * 導(dǎo)出或下載 Excel 公用方法
     *
     * @param response 當(dāng)前請求的 HttpServletResponse
     * @param rows     需要寫入的數(shù)據(jù) List
     * @param fileName 最終文件名
     */
    public static void export(HttpServletResponse response, List<Map<String, Object>> rows, List<String> headers, String fileName) {
        // 獲取 Writer
        ExcelWriter writer = ExcelUtil.getWriter(true);
        // 寫入表頭
        writer = writer.writeHeadRow(headers);
        // 若是有數(shù)據(jù) 則寫入數(shù)據(jù)
        if (CollectionUtils.isNotEmpty(rows)) {
            writer.write(rows);
        }
        Workbook workbook = writer.getWorkbook();
        CellStyle defaultCellStyle = StyleUtil.createDefaultCellStyle(workbook);
        DataFormat format = writer.getWorkbook().createDataFormat();
        // 默認(rèn)為 文本格式
        defaultCellStyle.setDataFormat(format.getFormat("@"));
        // 默認(rèn)為 居中
        defaultCellStyle.setAlignment(HorizontalAlignment.CENTER);
        for (int i = 0; i < headers.size(); i++) {
            String h = headers.get(i);
            h = h == null ? " " : h;
            writer.setColumnStyle(i, defaultCellStyle);
            // 默認(rèn)寬度為 3 * 表頭字符數(shù)
            writer.setColumnWidth(i, 3 * h.length());
        }
        try {
            // 彈出下載對話框的文件名，不能為中文，中文請自行編碼
            fileName = URLUtil.encode(fileName);
            response.setHeader("Access-Control-Expose-Headers", "Content-Disposition");
            response.setHeader("Content-Disposition", "attachment;filename=" + fileName + ".xlsx");
            response.setContentType(ExcelUtil.XLSX_CONTENT_TYPE);
            // 輸出
            ServletOutputStream out = response.getOutputStream();
            writer.flush(out, true);
            // 關(guān)閉writer，釋放內(nèi)存
            writer.close();
            //此處記得關(guān)閉輸出Servlet流
            IoUtil.close(out);
        } catch (IOException e) {
            e.printStackTrace();
            throw new RRException(BaseErrorEnum.COMMON_ERROR, "下載文件失敗!\n" + e.getMessage());
        }
    }

    /**
     * 讀取上傳到后臺的excel
     *
     * @param file MultipartFile 上傳的文件
     * @return 數(shù)據(jù)列表
     * @throws IOException e
     */
    public static List<Map<String, Object>> readExcelRows(MultipartFile file) throws IOException {
        return ExcelUtil.getReader(file.getInputStream()).readAll();
    }
}

// cn.hutool.poi.excel.ExcelWriter#merge(int, int, int, int, java.lang.Object, boolean)
	/**
	 * 合并某行的單元格，并寫入對象到單元格<br>
	 * 如果寫到單元格中的內(nèi)容非null，行號自動+1，否則當(dāng)前行號不變<br>
	 * 樣式為默認(rèn)標(biāo)題樣式，可使用{@link #getHeadCellStyle()}方法調(diào)用后自定義默認(rèn)樣式
	 *
	 * @param firstRow         起始行，0開始
	 * @param lastRow          結(jié)束行，0開始
	 * @param firstColumn      起始列，0開始
	 * @param lastColumn       結(jié)束列，0開始
	 * @param content          合并單元格后的內(nèi)容
	 * @param isSetHeaderStyle 是否為合并后的單元格設(shè)置默認(rèn)標(biāo)題樣式，只提取邊框樣式
	 * @return this
	 * @since 4.0.10
	 */
    public ExcelWriter merge(int firstRow, int lastRow, int firstColumn, int lastColumn, Object content, boolean isSetHeaderStyle) {
		Assert.isFalse(this.isClosed, "ExcelWriter has been closed!");

		CellStyle style = null;
		if (null != this.styleSet) {
			style = styleSet.getStyleByValueType(content, isSetHeaderStyle);
		}

		return merge(firstRow, lastRow, firstColumn, lastColumn, content, style);
	}