springboot将list<Map>集合导出为，固定列名，将map的键和值作为两列内容，自动分配列宽的Excel文件

可以使用Apache POI来实现将List<Map>集合导出为Excel文件。

步骤如下：

1. 创建Excel工作簿和工作表。

Workbook workbook = new XSSFWorkbook();
Sheet sheet = workbook.createSheet("Sheet1");

2. 创建表头，并设置列宽。

Row headerRow = sheet.createRow(0);
CellStyle headerStyle = workbook.createCellStyle();
headerStyle.setAlignment(HorizontalAlignment.CENTER);
headerStyle.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.getIndex());
headerStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);

Font headerFont = workbook.createFont();
headerFont.setBold(true);
headerStyle.setFont(headerFont);

int colNum = 0;
for (String key : dataList.get(0).keySet()) {
    Cell cell = headerRow.createCell(colNum++);
    cell.setCellValue(key);
    cell.setCellStyle(headerStyle);

    sheet.setColumnWidth(colNum, (key.length() + 4) * 256);
}

3. 填充数据。

int rowNum = 1;
for (Map<String, Object> map : dataList) {
    Row row = sheet.createRow(rowNum++);
    int colNum = 0;
    for (String key : map.keySet()) {
        Cell cell = row.createCell(colNum++);
        cell.setCellValue(String.valueOf(map.get(key)));
    }
}

4. 将工作簿写入输出流中。

workbook.write(outputStream);
workbook.close();

完整代码示例：

public void exportExcel(List<Map<String, Object>> dataList, OutputStream outputStream) throws IOException {
    Workbook workbook = new XSSFWorkbook();
    Sheet sheet = workbook.createSheet("Sheet1");

    Row headerRow = sheet.createRow(0);
    CellStyle headerStyle = workbook.createCellStyle();
    headerStyle.setAlignment(HorizontalAlignment.CENTER);
    headerStyle.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.getIndex());
    headerStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND);

    Font headerFont = workbook.createFont();
    headerFont.setBold(true);
    headerStyle.setFont(headerFont);

    int colNum = 0;
    for (String key : dataList.get(0).keySet()) {
        Cell cell = headerRow.createCell(colNum++);
        cell.setCellValue(key);
        cell.setCellStyle(headerStyle);

        sheet.setColumnWidth(colNum, (key.length() + 4) * 256);
    }

    int rowNum = 1;
    for (Map<String, Object> map : dataList) {
        Row row = sheet.createRow(rowNum++);
        int colNum = 0;
        for (String key : map.keySet()) {
            Cell cell = row.createCell(colNum++);
            cell.setCellValue(String.valueOf(map.get(key)));
        }
    }

    workbook.write(outputStream);
    workbook.close();
}