@Target(value=PARAMETER) @Retention(value=RUNTIME) @Documented public @interface RequestParam
Supported for annotated handler methods in Spring MVC and Spring WebFlux as follows:
ModelAttribute.
 If the method parameter type is Map and a request parameter name
 is specified, then the request parameter value is converted to a Map
 assuming an appropriate conversion strategy is available.
 
If the method parameter is Map<String, String> or
 MultiValueMap<String, String>
 and a parameter name is not specified, then the map parameter is populated
 with all request parameter names and values.
RequestMapping, 
RequestHeader, 
CookieValue| Modifier and Type | Optional Element and Description | 
|---|---|
String | 
defaultValue
The default value to use as a fallback when the request parameter is
 not provided or has an empty value. 
 | 
String | 
name
The name of the request parameter to bind to. 
 | 
boolean | 
required
Whether the parameter is required. 
 | 
String | 
value
Alias for  
name(). | 
public abstract boolean required
Defaults to true, leading to an exception being thrown
 if the parameter is missing in the request. Switch this to
 false if you prefer a null value if the parameter is
 not present in the request.
 
Alternatively, provide a defaultValue(), which implicitly
 sets this flag to false.
public abstract String defaultValue
Supplying a default value implicitly sets required() to
 false.