java将poi生成的excel文件以流的形式通过请求返回给前端

可以通过以下步骤将poi生成的excel文件以流的形式通过请求返回给前端：

1. 使用poi创建excel文件并将其写入OutputStream中：

Workbook workbook = new XSSFWorkbook();
Sheet sheet = workbook.createSheet("Sheet1");
Row row = sheet.createRow(0);
Cell cell = row.createCell(0);
cell.setCellValue("Hello World!");
OutputStream outputStream = new ByteArrayOutputStream();
workbook.write(outputStream);

2. 将OutputStream转换为ByteArrayInputStream：

ByteArrayInputStream inputStream = new ByteArrayInputStream(((ByteArrayOutputStream) outputStream).toByteArray());

3. 在返回响应时，将ByteArrayInputStream中的内容写入response的输出流中：

response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-Disposition", "attachment;filename=test.xlsx");
byte[] buffer = new byte[1024];
int len;
while ((len = inputStream.read(buffer)) != -1) {
    response.getOutputStream().write(buffer, 0, len);
}
inputStream.close();

完整代码示例：

@RequestMapping("/downloadExcel")
public void downloadExcel(HttpServletResponse response) throws IOException {
    Workbook workbook = new XSSFWorkbook();
    Sheet sheet = workbook.createSheet("Sheet1");
    Row row = sheet.createRow(0);
    Cell cell = row.createCell(0);
    cell.setCellValue("Hello World!");
    OutputStream outputStream = new ByteArrayOutputStream();
    workbook.write(outputStream);
    ByteArrayInputStream inputStream = new ByteArrayInputStream(((ByteArrayOutputStream) outputStream).toByteArray());
    response.setContentType("application/vnd.ms-excel");
    response.setHeader("Content-Disposition", "attachment;filename=test.xlsx");
    byte[] buffer = new byte[1024];
    int len;
    while ((len = inputStream.read(buffer)) != -1) {
        response.getOutputStream().write(buffer, 0, len);
    }
    inputStream.close();
}