How to convert collection to csv with jackson in java spring?

I have a problem to convert a java.util.Collection to a csv file with jackson.

In the following code you can see a method to convert the collection to a csv-string.

But i need a method to convert the collection with com.fasterxml.jackson.
The Enum "DownloadType" get the column and headerlines for csv file.

Do you have an idea to fix them?

@RequestMapping(value = "/csv",
produces = {"text/csv"},
consumes = {"application/json"},
method = RequestMethod.POST)
public ResponseEntity<Object> exportCsv()
{
ResponseEntity<Object> response = null;
try
{
HttpHeaders headers = new HttpHeaders();
headers.add(HttpHeaders.CONTENT_TYPE, "text/csv; charset=UTF-8");
headers.add(HttpHeaders.CACHE_CONTROL, "no-store, must-revalidate");
headers.add(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename="export.csv"");
headers.add(HttpHeaders.EXPIRES, "0");

byte csvBytes = null;
byte headerBytes = null;
byte lineBytes = null;
CsvMapper mapper = new
Collection<User> users = getUsers()
headerBytes = DownloadType.USER.getHeaderLine().getBytes("UTF-8");
lineBytes = mapper.writer(DownloadType.USER.getCsvSchema()).writeValueAsBytes(users);
if (headerBytes != null && lineBytes != null)
{
csvBytes = new byte[headerBytes.length + lineBytes.length];
System.arraycopy(headerBytes, 0, csvBytes, 0, headerBytes.length);
System.arraycopy(lineBytes, 0, csvBytes, headerBytes.length, lineBytes.length);
}
response = new ResponseEntity<>(csvBytes, headers, HttpStatus.OK);


}
catch (Exception e)
{
LOG.error(e.getMessage(), e);
}
return response;
}


1 Answer
1

Maybe try something like this. By writing the data directly to the servlet response the string will get returned directly back to the client as is without formatting or post-processing.

@RequestMapping(value = "/csv",
produces = {"text/csv"},
consumes = {"application/json"},
method = RequestMethod.POST)
public void exportCsv(HttpServletResponse response)
{
...
String headerString = DownloadType.USER.getHeaderLine()
String data = mapper.writer(DownloadType.USER.getCsvSchema()).writeValueAsString(users);
response.setContentType("text/plain; charset=utf-8");
response.getWriter().print(headerString);
response.getWriter().print(data);


Adapted from:
How to Return CSV Data in Browser From Spring Controller

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