servlet 过滤器如何识别下一个目标是另一个过滤器还是 servlet/jsp? [英] How does a servlets filter identify next destination is another filter or a servlet/jsp?

问题描述

我们通常会在 web.xml 中为 servlet 中的任何过滤器编写 <url-pattern>/*</url-pattern>.

We usually end up with writing <url-pattern>/*</url-pattern> in web.xml for any Filter in servlets.

<filter-mapping>
    <filter-name>requestRedirectorFilter</filter-name>
    <url-pattern>/action</url-pattern>
</filter-mapping>`.  

现在我的疑问是 java 如何识别下一个 servlet/jsp 是哪个?因为我们通过

Now my doubt is how java identifies which is next servlet/jsp is? Because any request we make through

request.getRequestDispatcher("/ABCXYZ").forward(request, (HttpServletResponse)servletResponse);

要在下一个 servlet/jsp 上导航，默认情况下容器将在 web.xml 中搜索.在 web.xml 中，/* 已经存在于我们使用的过滤器中.正是在这里，实际问题开始了.

to navigate on next servlet/jsp, container by default is going to search in web.xml. And in web.xml <url-pattern>/*</url-pattern> is already there for the filter we use. Exactly here actual problem begins.

如果 <url-pattern>/*</url-pattern> [它充当任何请求的通用接收器] 已经存在于 web.xml 中，那么容器如何知道遵循 /ABCXYZ 而不是 /* ?请分享您对这方面的看法和知识.

If <url-pattern>/*</url-pattern> [which is acting like a universal receiver for any request] is already there in web.xml then How the heck container knows to follow <url-pattern>/ABCXYZ</url-pattern> instead <url-pattern>/*</url-pattern> ? Please share your views and knowledge on this front.

推荐答案

Servlet 匹配过程

一个请求可能在给定的上下文中匹配多个 servlet-mapping.servlet 容器使用简单的匹配过程来确定最佳匹配.

A request may match more than one servlet-mapping in a given context. The servlet container uses a straightforward matching procedure to determine the best match.

匹配过程有四个简单的规则.

• 首先，与通配符路径匹配相比，容器更喜欢精确路径匹配.

其次，容器更喜欢匹配最长的模式.

Second, the container prefers to match the longest pattern.

第三，容器更喜欢路径匹配而不是文件类型匹配.

Third, the container prefers path matches over filetype matches.

最后，模式 / 总是匹配任何没有其他模式匹配的请求.

Finally, the pattern <url-pattern>/</url-pattern> always matches any request that no other pattern matches.

例如，上下文 web.xml 文件可以将在线目录的主页映射到一种模式，将目录的搜索页面映射到不同的模式，如下所示:

For example, a context web.xml file can map the home page for an online catalog to one pattern and the search page for the catalog to a different pattern, as shown below:

<servlet-mapping>
  <servlet-name>catalogBrowse</servlet-name>
  <url-pattern>/Catalog/*</url-pattern>
</servlet-mapping>

<servlet-mapping>
  <servlet-name>catalogSearch</servlet-name>
  <url-pattern>/Catalog/search/*</url-pattern>
</servlet-mapping>

下图说明了上下文的匹配过程.由于容器更喜欢匹配最长模式，因此包含 /Catalog/search/ 的 URL 始终匹配 catalogSearch 的映射，而不是 catalogBrowse 的映射.

Below figure illustrates the matching process for a context. Since the container prefers to match the longest pattern, a URL that includes /Catalog/search/ always matches the mapping for catalogSearch rather than the mapping for catalogBrowse.

网址格式匹配

如果您不感兴趣，请从以下链接复制.

请查看 URL 模式，其中详细描述了示例.

Please have a look at URL Patterns where it is described in detail with examples.

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