handleExportXls(fileName) {
    if (!fileName || typeof fileName != 'string') {
        fileName = '导出文件'
    }
    let param = this.getQueryParams()
    param.instanceId = this.instance.id
    if (this.selectedRowKeys && this.selectedRowKeys.length > 0) {
        param['selections'] = this.selectedRowKeys.join(',')
    }
    console.log('导出参数', param)
    downFile(this.url.exportXlsUrl, param).then((data) => {
        if (!data) {
            this.$message.warning('文件下载失败')
            return
        }
        if (typeof window.navigator.msSaveBlob !== 'undefined') {
            window.navigator.msSaveBlob(new Blob([data], { type: 'application/vnd.ms-excel' }), fileName + '.xls')
        } else {
            let url = window.URL.createObjectURL(new Blob([data], { type: 'application/vnd.ms-excel' }))
            let link = document.createElement('a')
            link.style.display = 'none'
            link.href = url
            link.setAttribute('download', fileName + '.xls')
            document.body.appendChild(link)
            link.click()
            document.body.removeChild(link) //下载完成移除元素
            window.URL.revokeObjectURL(url) //释放掉blob对象
        }
    })
}

@RequestMapping(value = "/exportXls")
public void exportXls(HttpServletRequest request, HttpServletResponse response) {
    try {
        List<Map<String,Object>> dataList = new ArrayList<Map<String,Object>>();
        Map<String,Object> map1 = new HashMap<>();
        map1.put("name","小明");
        map1.put("age","21");
        map1.put("degree","36");
        map1.put("link_name","小八");
        map1.put("link_age","33");
        dataList.add(map1);
        Map<String,Object> map2 = new HashMap<>();
        map2.put("name","小王");
        map2.put("age","24");
        map2.put("degree","37");
        map2.put("link_name","小六");
        map2.put("link_age","26");
        dataList.add(map2);
        List<ExcelExportEntity> entityList = new ArrayList<>();
        // 一般表头使用这种两个参数的构造器
        ExcelExportEntity e1 = new ExcelExportEntity("姓名","name");
        ExcelExportEntity e2 = new ExcelExportEntity("年龄","age");
        ExcelExportEntity e3 = new ExcelExportEntity("体温","degree");
        entityList.add(e1);
        entityList.add(e2);
        entityList.add(e3);
        // 需要被设置成子表头的使用这种三个参数的构造器,设置colspan为true
        ExcelExportEntity e5 = new ExcelExportEntity("姓名","link_name",true);
        ExcelExportEntity e6 = new ExcelExportEntity("年龄","link_age", true);
        entityList.add(e5);
        entityList.add(e6);
        // 合并表头也需要设置colspan为true
        ExcelExportEntity e4 = new ExcelExportEntity("紧急联系人","linkman",true);
        List<String> sub = new ArrayList<>();
        sub.add("link_name");
        sub.add("link_age");
        // 还需要设置一个子表头key的集合
        e4.setSubColumnList(sub);
        entityList.add(e4);
        ExcelExportEntity en = new ExcelExportEntity("总分", "total", 30);
        entityList.add(en);
        Workbook workbook = ExcelExportUtil.exportExcel(new ExportParams(null, "sheetName"),entityList,dataList);
        // 重点，导出结果写入流中
        ServletOutputStream out = response.getOutputStream();
        workbook.write(out);
        out.flush();
        out.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

总结：

• 需要注意把Workbook写入response中

To Be Continued！😎