Output and delivery

Writing to a file and attaching to an e-mail

// To a file: stream method
try (OutputStream out = Files.newOutputStream(Path.of("report.xlsx"))) {
    sheetsmith.generate(sheets, out);
}

// As an attachment: byte method
byte[] file = sheetsmith.generate(sheets);
helper.addAttachment("report.xlsx", new ByteArrayResource(file),
        "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");

Download from a plain servlet

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
    List<SheetData<?>> sheets = List.of(SheetData.of("Customers", CustomerRow.class, loadCustomers()));
    byte[] file = sheetsmith.generate(sheets);   // errors happen here, before the response is touched
    response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
    response.setHeader("Content-Disposition", "attachment; filename=\"customers.xlsx\"");
    response.setContentLength(file.length);
    response.getOutputStream().write(file);
}

For the Spring MVC equivalent see section 2.3.

Large exports

@ExcelSheet(autoSizeColumns = false, freezeHeader = true)
public record MovementRow(
        @ExcelColumn(header = "Id", order = 10, width = 12) long id,
        @ExcelColumn(header = "Date", order = 20, width = 12, format = "dd/mm/yyyy") LocalDate date,
        @ExcelColumn(header = "Description", order = 30, width = 50) String description,
        @ExcelColumn(header = "Amount", order = 40, width = 14, format = "#,##0.00") BigDecimal amount) {
}

Explicit widths and no automatic sizing; a heap sized from the measurements in section 12.3; bounded concurrency; data split across files beyond a few hundred thousand rows.