Custom Object as a #RequestParam - spring

Question

I have a paginated endpoint that looks like this /api/clients?range=0-25.
I'd like the getClients() method in my ClientController to directly receive an instance of a custom Range object rather than having to validate a "0-25" String but I'm having trouble figuring this out.
#Getter
final class Range {
#Min(0)
private Integer offset = 0;
#Min(1)
private Integer limit = 25;
}
#ResponseBody
#GetMapping(params = { "range" })
public ResponseEntity<?> getAllClients(#RequestParam(value = "range", required = false) QueryRange queryRange, final HttpServletResponse response) {
...
}
I'm not sure how to instruct the Controller to correctly deserialize the "0-25" string into the Range...

Answer 1

You can use a Converter<S, T>, as shown below:
#Component
public class RangeConverter implements Converter<String, Range> {
#Override
public Range convert(String source) {
String[] values = source.split("-");
return new Range(Integer.valueOf(values[0]), Integer.valueOf(values[1]));
}
}
You also could handle invalid values according to your needs. If you use the above converter as is, the attempt to convert an invalid value such as 1-x will result in a ConversionFailedException.

Answer 2

You can also do the following it seems :
public class QueryRangeEditor extends PropertyEditorSupport {
private static final Pattern PATTERN = Pattern.compile("^([1-9]\\d*|0)-([1-9]\\d*|0)$");
#Override
public void setAsText(String text) throws IllegalArgumentException {
final QueryRange range = new QueryRange();
Matcher matcher = PATTERN.matcher(text);
if (matcher.find()) {
range.setOffset(Integer.valueOf(matcher.group(1)));
range.setLimit(Integer.valueOf(matcher.group(2)));
} else {
throw new IllegalArgumentException("OI"); // todo - replace
}
setValue(range);
}
}
#InitBinder
public void initBinder(WebDataBinder binder) {
binder.registerCustomEditor(QueryRange.class, new QueryRangeEditor());
}
But #cassiomolin's looks cleaner...