web.xml 中的 Java 项目未知枚举

Question

我正在学习过滤器。所以我的 web.xml 中有以下代码：

    <filter>
    <filter-name>asyncFilter</filter-name>
    <filter-class>el.test.AnyRequestFilter</filter-class>
    <async-supported>true</async-supported>
</filter>

<filter-mapping>
    <filter-name>asyncFilter</filter-name>
    <url-pattern>/*</url-pattern>
    <dispatcher>ASYNC</dispatcher>
</filter-mapping>

当我写是自动完成我ASYNC，但之后它变成红色，IntelliJ 告诉我错误是unknown enum。 这是为什么？ 感谢您的关注。

附：我也有以下代码的问题：

<error-page>
    <location>/WEB-INF/jsp/view/badRequest.jsp</location>
    <error-code>404</error-code>
</error-page>

在<error-code> 上写的是no child element expected at this point，但代码正在运行（我可以运行它）。

Answer 1

来自https://docs.oracle.com/cd/E19879-01/819-3669/bnagf/index.html

4.In the Add Filter Mapping dialog, select one of the following dispatcher types:

REQUEST: Only when the request comes directly from the client
FORWARD: Only when the request has been forwarded to a component (see Transferring Control to Another Web Component)
INCLUDE: Only when the request is being processed by a component that has been included (see Including Other Resources in the Response)
ERROR: Only when the request is being processed with the error page mechanism (see Handling Servlet Errors)

所以 ASYNC 不是有效值。

编辑：它似乎是在 javaee 6 中添加的：http://docs.oracle.com/javaee/6/tutorial/doc/bnagb.html

所以你的项目和 IDE 可能存在 JRE/JDK 版本的配置问题。