Spring Boot Controller export an Excel

Question

I have a java/spring boot application where I want to build an API endpoint that creates and returns a downloadable excel file. Here is my controller endpoint:

@         


        

Answer 1

Letting controller know is always better what it is going to write using ReponseEntity. At service level just create and play around the objects. @RestController or @Controller doesn't matter here.

What you are looking forward for in your controller is somewhat like this (sample) -

@GetMapping(value = "/alluserreportExcel")
public ResponseEntity excelCustomersReport() throws IOException {
    List users = (List) userService.findAllUsers();
    ByteArrayInputStream in = GenerateExcelReport.usersToExcel(users);
    // return IO ByteArray(in);
    HttpHeaders headers = new HttpHeaders();
    // set filename in header
    headers.add("Content-Disposition", "attachment; filename=users.xlsx");
    return ResponseEntity.ok().headers(headers).body(new InputStreamResource(in));
}

Generate Excel Class -

public class GenerateExcelReport {

public static ByteArrayInputStream usersToExcel(List users) throws IOException {
...
...
//your list here
int rowIdx = 1;
        for (AppUser user : users) {
            Row row = sheet.createRow(rowIdx++);

            row.createCell(0).setCellValue(user.getId().toString());
            ...
        }

  workbook.write(out);
  return new ByteArrayInputStream(out.toByteArray());

and finally, somewhere, in your view -

Export all users to MS-Excel

For full example, take a peek - here, here and here.