RequestParam (Spring Framework 4.3.30.RELEASE API)

```
@Target(PARAMETER)
@Retention(RUNTIME)
@Documented
public @interface RequestParam
```
Annotation which indicates that a method parameter should be bound to a web request parameter.
Supported for annotated handler methods in Servlet and Portlet environments.
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.
从以下版本开始:
2.5
作者:
Arjen Poutsma, Juergen Hoeller, Sam Brannen
另请参阅:
RequestMapping, RequestHeader, CookieValue, RequestMappingHandlerAdapter, AnnotationMethodHandlerAdapter, AnnotationMethodHandlerAdapter

可选元素概要

可选元素
修饰符和类型	可选元素	说明
`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()`.

- 元素详细资料
  - value
```
@AliasFor("name")
String value
```
    Alias for name().
    默认值:
    ""
- - name
```
@AliasFor("value")
String name
```
    The name of the request parameter to bind to.
    从以下版本开始:
    4.2
    默认值:
    ""
- - required
```
boolean required
```
    Whether the parameter is 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.
    默认值:
    true
- - defaultValue
```
String defaultValue
```
    The default value to use as a fallback when the request parameter is not provided or has an empty value.
    Supplying a default value implicitly sets required() to false.
    默认值:
    "\n\t\t\n\t\t\n\ue000\ue001\ue002\n\t\t\t\t\n"