[Kotlin] java POI 를 이용한 write / download

@GetMapping(value = ["/excel"])
fun excel(res: HttpServletResponse,excelReq: ExcelReq/*, excelForm: ExcelForm*/) {

    val savePath = "/Users/jwkim_macbook/Desktop/exceltest.xlsx"

    try {
        XSSFWorkbook().use { wb2 ->
            ByteArrayOutputStream().use { fileOut ->
                FileOutputStream(savePath).use { fos ->
                    val sheet1: Sheet = wb2.createSheet("Sheet1")
                    val style: CellStyle = wb2.createCellStyle()
                    style.setBorderBottom(BorderStyle.THIN)

                    val header: Row = sheet1.createRow(0);
                    var headerCell: Cell = header.createCell(0)
                    headerCell.cellStyle = style
                    headerCell.setCellValue("no")
                    headerCell = header.createCell(1)
                    headerCell.cellStyle = style
                    headerCell.setCellValue("no1")
                    headerCell = header.createCell(2)
                    headerCell.cellStyle = style
                    headerCell.setCellValue("no2")
                    headerCell = header.createCell(3)
                    headerCell.cellStyle = style
                    headerCell.setCellValue("no3")
                    //Write Excel File

                    val excelList = excelManager.abnormal()
                    excelList.forEachIndexed { index, excelInfo ->
                        val row: Row = sheet1.createRow(index+1)
                        var cell: Cell = row.createCell(0)
                        cell.setCellValue(excelInfo.num1)
                        cell = row.createCell(1)
                        cell.setCellValue(excelInfo.num2)
                        cell = row.createCell(2)
                        cell.setCellValue(excelInfo.num3)
                        cell = row.createCell(3)
                        cell.setCellValue(excelInfo.num4)

                    }
                    wb2.write(fileOut)
                    val filein: InputStream = ByteArrayInputStream(fileOut.toByteArray())
                    val opc: OPCPackage = OPCPackage.open(filein)
                    val fileSystem = POIFSFileSystem()
                    val encryptionInfo = EncryptionInfo(EncryptionMode.agile)
                    val encryptor: Encryptor = encryptionInfo.encryptor
                    encryptor.confirmPassword(excelReq.pw)
                    opc.save(encryptor.getDataStream(fileSystem))
                    fileSystem.writeFilesystem(fos)
                }
            }
        }
    } catch (e: IOException) {
        logger.error(e.message, e)
    } catch (e: InvalidFormatException) {
        logger.error(e.message, e)
    } catch (e: GeneralSecurityException) {
        logger.error(e.message, e)
    }

    val attachFile = File(savePath)
    val inputStream: InputStream = FileInputStream(attachFile)

    try{
        val encodedFileName = 
        "${URLEncoder.encode("exceltest", "UTF-8").replace("+", "%20")}.xlsx"
        //val encodedFileName = "exceltest.xlsx"

        //val ext = ".${attachFile.extension}"
        res.addHeader(HttpHeaders.CONTENT_DISPOSITION, 
                     "attachment; filename=\"$encodedFileName\"; 
                     filename*=utf-8''$encodedFileName"
        )
        res.setContentLengthLong(attachFile.length())
        res.addHeader(HttpHeaders.PRAGMA, "No-cache") //HTTP 1.0
        res.addDateHeader(HttpHeaders.EXPIRES, 0)
        res.addHeader(HttpHeaders.CACHE_CONTROL, "no-cache")
        res.contentType = Files.probeContentType(attachFile.toPath())

        IOUtils.copy(inputStream, res.outputStream)
    }catch(e: IOException){
        e.printStackTrace()
        throw ErrorResp.getInternalServerError().apply {
            addError("attachFile", "e", e.localizedMessage)
        }
    }finally {
        IOUtils.closeQuietly(inputStream)
        res.flushBuffer()
    }

}

별다른 설명 필요없는 간단한 excel 쓰기 및 다운로드.