这个注解是/** * Mapped onto a entity bean property that represents the user id of * who created the entity> * <p> * To use this annotation you need to implement CurrentUserProvider. * The type of the bean property should match the type returned by * CurrentUserProvider. * </p> * <h3>Example:</h3> * <pre>{@code * * @WhoCreated * String whoCreated; * * }</pre> */ @Target({ElementType.FIELD}) @Retention(RetentionPolicy.RUNTIME) public @interface WhoCreated { }

根据您提供的代码，`@WhoCreated` 是一个自定义注解，用于标记实体类中表示创建者的属性。根据注解的描述，它需要与 `CurrentUserProvider` 接口一起使用，并且被标记的属性的类型应该与 `CurrentUserProvider` 返回的类型相匹配。

以下是使用 `@WhoCreated` 注解的示例代码：

public class MyEntity {
    // 其他字段...

    @WhoCreated
    private String whoCreated;

    // 其他方法...
}

在上述示例中，`whoCreated` 属性被标记为 `@WhoCreated` 注解，表示它是用于保存创建者信息的字段。

要正确使用 `@WhoCreated` 注解，您需要实现一个 `CurrentUserProvider` 接口，并确保返回的类型与被标记属性的类型相匹配。`CurrentUserProvider` 接口负责提供当前用户的信息，以便在创建实体对象时将其赋值给被标记的属性。

请注意，以上代码只是示例，并且假设您已经实现了 `CurrentUserProvider` 接口。实际情况可能因您所使用的框架或库而有所不同。

如果您需要进一步的帮助，请提供有关 `CurrentUserProvider` 接口的细节或相关代码的信息，我将尽力协助您解决问题。

相关问题

You are creating a Web application for the book shop by using Spring MVC. When a user sends a request for theURL, /SearchBook.htm page in this Web application, the request needs to be handled by theSearchBookController class defined in the controller package of the Web application. For this, you used thefollowing code snippet:<beans> <bean id="ControllerHandlerMapping" class=org.springframework.web.servlet.mvcsupport,SimpleUrlHandlerMapping"/><bean class="controller SearchBookController"></beans> However, the preceding code snippet does not forward the request to the SearchBookController class. Analyze theproblem and provide the correct code snippet.

The code snippet provided in the question is incorrect because the `SimpleUrlHandlerMapping` bean is not properly configured to handle the URL mapping for the `SearchBookController`. To correctly map the URL `/SearchBook.htm` to the `SearchBookController`, you should use the following code snippet:

<beans>
    <bean id="handlerMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
        <property name="mappings">
            <props>
                <prop key="/SearchBook.htm">searchBookController</prop>
            </props>
        </property>
    </bean>
    
    <bean id="searchBookController" class="controller.SearchBookController"/>
</beans>

In this code snippet, we are using the `SimpleUrlHandlerMapping` bean to map the URL `/SearchBook.htm` to the `searchBookController` bean, which is an instance of the `SearchBookController` class. The `handlerMapping` bean is configured with a `mappings` property that contains a `props` element with a single URL mapping for `/SearchBook.htm`. The `searchBookController` bean is defined as an instance of the `SearchBookController` class and is mapped to the `searchBookController` bean ID. This configuration ensures that requests to the `/SearchBook.htm` URL are handled by the `SearchBookController` class.

## Problem 6: Deep Map Implement `deep_map`, which takes a function `f` and a `link`. It returns a *new* linked list with the same structure as `link`, but with `f` applied to any element within `link` or any `Link` instance contained in `link`. The `deep_map` function should recursively apply `fn` to each of that `Link`'s elements rather than to that `Link` itself. *Hint*: You may find the built-in `isinstance` function useful. You can also use the `type(link) == Link` to check whether an object is a linked list. ```python def deep_map(f, link): """Return a Link with the same structure as link but with fn mapped over its elements. If an element is an instance of a linked list, recursively apply f inside that linked list as well. >>> s = Link(1, Link(Link(2, Link(3)), Link(4))) >>> print(deep_map(lambda x: x * x, s)) <1 <4 9> 16> >>> print(s) # unchanged <1 <2 3> 4> >>> print(deep_map(lambda x: 2 * x, Link(s, Link(Link(Link(5)))))) <<2 <4 6> 8> <<10>>> """ "*** YOUR CODE HERE ***"

以下是`deep_map`函数的实现：

class Link:
    empty = ()
    def __init__(self, first, rest=empty):
        assert rest is Link.empty or isinstance(rest, Link)
        self.first = first
        self.rest = rest

    def __repr__(self):
        if self.rest is not Link.empty:
            rest_str = ' ' + repr(self.rest)
        else:
            rest_str = ''
        return '<' + str(self.first) + rest_str + '>'

    def __len__(self):
        return 1 + len(self.rest)

    def __getitem__(self, i):
        if i == 0:
            return self.first
        else:
            return self.rest[i-1]

    def __setitem__(self, i, value):
        if i == 0:
            self.first = value
        else:
            self.rest[i-1] = value


def deep_map(f, link):
    """
    Return a Link with the same structure as link but with f mapped over
    its elements. If an element is an instance of a linked list, recursively
    apply f inside that linked list as well.
    """
    if link is Link.empty:
        return Link.empty
    elif isinstance(link, Link):
        return Link(deep_map(f, link.first), deep_map(f, link.rest))
    else:
        return f(link)

我们首先处理递归基，如果传入的`link`为空链表，则直接返回空链表。然后判断`link`是否是链表类型，如果是，则对`link`的第一个元素和剩余部分递归调用`deep_map`函数，并用它们创建一个新的链表返回。如果`link`不是链表类型，则直接将`f(link)`的结果返回。

我们可以测试`deep_map`函数的正确性：

s = Link(1, Link(Link(2, Link(3)), Link(4)))
print(deep_map(lambda x: x * x, s)) # <1 <4 9> 16>
print(s) # <1 <2 3> 4>
t = Link(s, Link(Link(Link(5))))
print(deep_map(lambda x: 2 * x, t)) # <<2 <4 6> 8> <<10>>