Request params Optional<List<String> and List<String> are inconsistent [SPR-15676]

[spring-projects-issues]

Ayush Kumar opened SPR-15676 and commented

When using List<String> as the request parameter, both key=val1,val2 and key=val1&key=val2 end up mapping to key = [val1, val2]

When using Optional<List<String>> as the request parameter
key=val1,val2 maps to key = Optional([val1,val2])
but key=val1&key=val2 maps to Optional([val1])

This makes RequestParam(..., required = false) List<String> behave differently from RequestParam(...) Optional<List<String>>, which seems unfortunate.

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Affects: 4.3.4

Issue Links:

• @RequestParam Optional<List<?>> not handling multiple params of the same name correctly [SPR-15857] #20412 @RequestParam Optional<List<?>> not handling multiple params of the same name correctly ("is duplicated by")
• Request parameters cannot bind to Optional<List<String>> [SPR-13418] #17997 Request parameters cannot bind to Optional<List>
• java.util.Optional MultipartFile[] @RequestParam argument is null in multipart/form-data POST [SPR-15918] #20472 java.util.Optional MultipartFile[] @RequestParam argument is null in multipart/form-data POST
• only one MultipartFile object populated when using an java.util.Optional MutipartFile array or list @RequestParam [SPR-15919] #20473 only one MultipartFile object populated when using an java.util.Optional MutipartFile array or list @RequestParam

Backported to: 4.3.12

1 votes, 3 watchers

[spring-projects-issues]

Ayush Kumar commented

Linked to #17997

[spring-projects-issues]

Juergen Hoeller commented

This turns out to be addressed by the fix for #20473. I've added dedicated tests for regular parameter values as well now.