WebArgumentResolver (Spring Framework 5.2.12.RELEASE API)

函数接口:
这是一个函数接口, 因此可用作 lambda 表达式或方法引用的赋值目标。
```
@FunctionalInterface
public interface WebArgumentResolver
```
SPI for resolving custom arguments for a specific handler method parameter. Typically implemented to detect special parameter types, resolving well-known argument values for them.
A typical implementation could look like as follows:
```
 public class MySpecialArgumentResolver implements WebArgumentResolver {

   public Object resolveArgument(MethodParameter methodParameter, NativeWebRequest webRequest) {
     if (methodParameter.getParameterType().equals(MySpecialArg.class)) {
       return new MySpecialArg("myValue");
     }
     return UNRESOLVED;
   }
 }
```
从以下版本开始:
2.5.2
作者:
Juergen Hoeller
另请参阅:
RequestMappingHandlerAdapter.setCustomArgumentResolvers(java.util.List<org.springframework.web.method.support.HandlerMethodArgumentResolver>)

字段概要
字段
修饰符和类型字段说明
static Object UNRESOLVED
Marker to be returned when the resolver does not know how to handle the given method parameter.

方法概要

所有方法实例方法抽象方法
修饰符和类型	方法	说明
`Object`	`resolveArgument(MethodParameter methodParameter, NativeWebRequest webRequest)`	Resolve an argument for the given handler method parameter within the given web request.

- 字段详细资料
  - UNRESOLVED
```
static final Object UNRESOLVED
```
    Marker to be returned when the resolver does not know how to handle the given method parameter.
- 方法详细资料
  - resolveArgument
```
@Nullable
Object resolveArgument(MethodParameter methodParameter,
                       NativeWebRequest webRequest)
                throws Exception
```
    Resolve an argument for the given handler method parameter within the given web request.
    参数:
    methodParameter - the handler method parameter to resolve
    webRequest - the current web request, allowing access to the native request as well
    返回:
    the argument value, or UNRESOLVED if not resolvable
    抛出:
    Exception - in case of resolution failure