Java Hutool 包工具类推荐 ExcelUtil详解

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

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

    /**
     * 导出或下载 Excel 公用方法
     *
     * @param response 当前请求的 HttpServletResponse
     * @param rows     需要写入的数据 List
     * @param fileName 最终文件名
     */
    public static void export(HttpServletResponse response, List<Map<String, Object>> rows, List<String> headers, String fileName) {
        // 获取 Writer
        ExcelWriter writer = ExcelUtil.getWriter(true);
        // 写入表头
        writer = writer.writeHeadRow(headers);
        // 若是有数据 则写入数据
        if (CollectionUtils.isNotEmpty(rows)) {
            writer.write(rows);
        }
        Workbook workbook = writer.getWorkbook();
        CellStyle defaultCellStyle = StyleUtil.createDefaultCellStyle(workbook);
        DataFormat format = writer.getWorkbook().createDataFormat();
        // 默认为 文本格式
        defaultCellStyle.setDataFormat(format.getFormat("@"));
        // 默认为 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);
            // 默认宽度为 3 * 表头字符数
            writer.setColumnWidth(i, 3 * h.length());
        }
        try {
            // 弹出下载对话框的文件名，不能为中文，中文请自行编码
            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);
            // 输出
            ServletOutputStream out = response.getOutputStream();
            writer.flush(out, true);
            // 关闭writer，释放内存
            writer.close();
            //此处记得关闭输出Servlet流
            IoUtil.close(out);
        } catch (IOException e) {
            e.printStackTrace();
            throw new RRException(BaseErrorEnum.COMMON_ERROR, "下载文件失败!\n" + e.getMessage());
        }
    }

    /**
     * 读取上传到后台的excel
     *
     * @param file MultipartFile 上传的文件
     * @return 数据列表
     * @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)
	/**
	 * 合并某行的单元格，并写入对象到单元格<br>
	 * 如果写到单元格中的内容非null，行号自动+1，否则当前行号不变<br>
	 * 样式为默认标题样式，可使用{@link #getHeadCellStyle()}方法调用后自定义默认样式
	 *
	 * @param firstRow         起始行，0开始
	 * @param lastRow          结束行，0开始
	 * @param firstColumn      起始列，0开始
	 * @param lastColumn       结束列，0开始
	 * @param content          合并单元格后的内容
	 * @param isSetHeaderStyle 是否为合并后的单元格设置默认标题样式，只提取边框样式
	 * @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);
	}