Type Conversion
Some annotated controller method arguments that represent String-based request input (for example,
@RequestParam
, @RequestHeader
, @PathVariable
, @MatrixVariable
, and @CookieValue
)
can require type conversion if the argument is declared as something other than String
.
For such cases, type conversion is automatically applied based on the configured converters.
By default, simple types (such as int
, long
, Date
, and others) are supported. Type conversion
can be customized through a WebDataBinder
(see DataBinder
) or by registering
Formatters
with the FormattingConversionService
(see Spring Field Formatting).
A practical issue in type conversion is the treatment of an empty String source value.
Such a value is treated as missing if it becomes null
as a result of type conversion.
This can be the case for Long
, UUID
, and other target types. If you want to allow null
to be injected, either use the required
flag on the argument annotation, or declare the
argument as @Nullable
.