If a default value is set, "required" is implicitly false.
See :
/**
* Whether the parameter is required.
* <p>Defaults to {@code true}, leading to an exception being thrown
* if the parameter is missing in the request. Switch this to
* {@code false} if you prefer a {@code null} value if the parameter is
* not present in the request.
* <p>Alternatively, provide a {@link #defaultValue}, which implicitly
* sets this flag to {@code false}.
*/
boolean required() default true;
/**
* The default value to use as a fallback when the request parameter is
* not provided or has an empty value.
* <p>Supplying a default value implicitly sets {@link #required} to
* {@code false}.
*/
String defaultValue() default ValueConstants.DEFAULT_NONE;
If a default value is set, "required" is implicitly false.
See :