spring mvc不能下载cab包等插件问题

default-servlet-handler

<!-- Handles HTTP GET requests for static resources by efficiently serving up static resources in the ${webappRoot}/resources directory -->

<default-servlet-handler/>

在配置文件中加上这句话。

Spring参考手册 mvc:default-servlet-handler

This tag allows for mapping the DispatcherServlet to "/" (thus overriding the mapping of the container's default Servlet), while still allowing static resource requests to be handled by the container's default Servlet. 
这个标签吧DispatcherServlet 映射到"/"（从而覆盖容器的默认servlet的映射），也允许容器默认的servlet处理静态资源的请求。
//我感觉这句的意思就是：DispatcherServlet把找不到的请求映射到默认的servlet，从而实现处理静态资源的请求。不知理解的对不对？

It configures a DefaultServletHttpRequestHandler with a URL mapping (given a lowest precedence order) of "/**". 
This handler will forward all requests to the default Servlet.
配置了DefaultServletHttpRequestHandler最后来处理"/**"的请求。
这个处理器会把所有的请求跳转到容器默认servlet。

To enable this feature using the default setup, simply include the tag in the form:
标签的默认设置就可以实现这个功能：
<mvc:default-servlet-handler/>
The caveat to overriding the "/" Servlet mapping is that the RequestDispatcher for the default Servlet must be retrieved by name rather than by path. 
覆盖"/"映射会导致默认servlet的RequestDispatcher必须用名字取回而不是路径。（不知道什么意思，是不是跟下一句有关联呐，使用名字找默认servlet）

The DefaultServletHttpRequestHandler will attempt to auto-detect the default Servlet for the container at startup time, using a list of known names for most of the major Servlet containers (including Tomcat, Jetty, Glassfish, JBoss, Resin, WebLogic, and WebSphere). 
DefaultServletHttpRequestHandler在容器启动是会使用主流web容器默认servlet的名称列表自动查找容器的默认servlet，包括Tomcat, Jetty, Glassfish, JBoss, Resin, WebLogic, and WebSphere。

If the default Servlet has been custom configured with a different name, or if a different Servlet container is being used where the default Servlet name is unknown, then the default Servlet's name must be explicitly provided as in the following example:
如果为默认servlet配置了新的名称，或者这个容器servlet名字不在spring列表中是，必须显式配置默认servlet的名字，如下：
<mvc:default-servlet-handler default-servlet-name="myCustomDefaultServlet"/>