java 生成excel （多级表头）导出

依赖工具包 

<dependencies>
    <dependency>
        <groupId>cn.hutool</groupId>
        <artifactId>hutool-all</artifactId>
        <version>5.3.5</version>
    </dependency>
</dependencies>
该工具包是对 Apache POI包的分装

    private void export(HttpServletResponse response, String fileName, List<?> projects, List<SummarizeDownloadColumns> columns) throws IOException {
        ExcelWriter bigWriter = ExcelUtil.getBigWriter();
       //创建一行空表头占个位置
        bigWriter.writeHeadRow(new LinkedList());
       //创建需要展示的的二级表头，{filedName,中文名}
        int lastCol = 0;
        for (int i = 0; i < columns.size(); i++) {
            if (columns.get(i).getChildren() != null) {
                for (int j = 0; j < columns.get(i).getChildren().size(); j++) {
                    bigWriter.addHeaderAlias(columns.get(i).getChildren().get(j).getProp(), columns.get(i).getChildren().get(j).getLabel() + columns.get(i).getProp());
                    bigWriter.setColumnWidth(lastCol++, 30);
                }
            }
        }
       //根据需要合并添加第一列表头
        bigWriter.merge(0, 1, 0, 0, columns.get(0).getLabel(), true);
        bigWriter.merge(0, 0, 1, 14, "第一类（个人）", true);
        bigWriter.merge(0, 0, 15, 28, "第一类（企业）", true);
        bigWriter.merge(0, 0, 29, 42, "第二类（个人）", true);
        bigWriter.merge(0, 0, 43, 56, "第二类（企业）", true);
        bigWriter.merge(0, 0, 57, 64, "总计项", true);

        // 只导出配置好的列名
        bigWriter.setOnlyAlias(true);
        bigWriter.write(projects, true);
        StyleSet styleSet = bigWriter.getStyleSet();
        styleSet.setWrapText();
        response.setContentType("application/vnd.ms-excel;charset=utf-8");
        response.setHeader("filename", URLEncoder.encode(fileName + ".xlsx", "UTF-8"));
        ServletOutputStream out = response.getOutputStream();
        bigWriter.flush(out, true);
        bigWriter.close();
        IoUtil.close(out);
    }

导出效果