Poison

关于 web.xml 中的通配符匹配问题

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临近下班，帮同事查了个路径匹配的问题，在此简单记录。问题简化后如下，同事在 web.xml 中配置的路径匹配如下：

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<servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/pc/*</url-pattern>
</servlet-mapping>

在 Spring MVC 中配置的注解为：@RequestMapping("/pc/**")，请求接口 /pc/index.htm 时服务器响应状态码为 404，经过调试，调用栈帧如下：

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getPathWithinServletMapping:192, UrlPathHelper (org.springframework.web.util)
getLookupPathForRequest:169, UrlPathHelper (org.springframework.web.util)
getHandlerInternal:310, AbstractHandlerMethodMapping (org.springframework.web.servlet.handler)
getHandlerInternal:62, AbstractHandlerMethodMapping (org.springframework.web.servlet.handler)
getHandler:350, AbstractHandlerMapping (org.springframework.web.servlet.handler)
getHandler:1188, DispatcherServlet (org.springframework.web.servlet)
doDispatch:964, DispatcherServlet (org.springframework.web.servlet)
doService:925, DispatcherServlet (org.springframework.web.servlet)
processRequest:974, FrameworkServlet (org.springframework.web.servlet)
doPost:877, FrameworkServlet (org.springframework.web.servlet)
service:652, HttpServlet (javax.servlet.http)
service:851, FrameworkServlet (org.springframework.web.servlet)
service:733, HttpServlet (javax.servlet.http)
internalDoFilter:231, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:109, HttpPutFormContentFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilter:52, WsFilter (org.apache.tomcat.websocket.server)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:200, CharacterEncodingFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
invoke:199, StandardWrapperValve (org.apache.catalina.core)
invoke:97, StandardContextValve (org.apache.catalina.core)
invoke:543, AuthenticatorBase (org.apache.catalina.authenticator)
invoke:143, StandardHostValve (org.apache.catalina.core)
invoke:81, ErrorReportValve (org.apache.catalina.valves)
invoke:690, AbstractAccessLogValve (org.apache.catalina.valves)
invoke:78, StandardEngineValve (org.apache.catalina.core)
service:343, CoyoteAdapter (org.apache.catalina.connector)
service:616, Http11Processor (org.apache.coyote.http11)
process:65, AbstractProcessorLight (org.apache.coyote)
process:818, AbstractProtocol$ConnectionHandler (org.apache.coyote)
doRun:1626, NioEndpoint$SocketProcessor (org.apache.tomcat.util.net)
run:49, SocketProcessorBase (org.apache.tomcat.util.net)
runWorker:1149, ThreadPoolExecutor (java.util.concurrent)
run:624, ThreadPoolExecutor$Worker (java.util.concurrent)
run:61, TaskThread$WrappingRunnable (org.apache.tomcat.util.threads)
run:748, Thread (java.lang)

关键的方法源码为：

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/**
 * Return the path within the servlet mapping for the given request,
 * i.e. the part of the request's URL beyond the part that called the servlet,
 * or "" if the whole URL has been used to identify the servlet.
 * <p>Detects include request URL if called within a RequestDispatcher include.
 * <p>E.g.: servlet mapping = "/*"; request URI = "/test/a" -> "/test/a".
 * <p>E.g.: servlet mapping = "/"; request URI = "/test/a" -> "/test/a".
 * <p>E.g.: servlet mapping = "/test/*"; request URI = "/test/a" -> "/a".
 * <p>E.g.: servlet mapping = "/test"; request URI = "/test" -> "".
 * <p>E.g.: servlet mapping = "/*.test"; request URI = "/a.test" -> "".
 * @param request current HTTP request
 * @return the path within the servlet mapping, or ""
 */
public String getPathWithinServletMapping(HttpServletRequest request) {
  String pathWithinApp = getPathWithinApplication(request);
  String servletPath = getServletPath(request);
  String sanitizedPathWithinApp = getSanitizedPath(pathWithinApp);
  String path;

  // If the app container sanitized the servletPath, check against the sanitized version
  if (servletPath.contains(sanitizedPathWithinApp)) {
    path = getRemainingPath(sanitizedPathWithinApp, servletPath, false);
  }
  else {
    path = getRemainingPath(pathWithinApp, servletPath, false);
  }

  if (path != null) {
    // Normal case: URI contains servlet path.
    return path;
  }
  else {
    // Special case: URI is different from servlet path.
    String pathInfo = request.getPathInfo();
    if (pathInfo != null) {
      // Use path info if available. Indicates index page within a servlet mapping?
      // e.g. with index page: URI="/", servletPath="/index.html"
      return pathInfo;
    }
    if (!this.urlDecode) {
      // No path info... (not mapped by prefix, nor by extension, nor "/*")
      // For the default servlet mapping (i.e. "/"), urlDecode=false can
      // cause issues since getServletPath() returns a decoded path.
      // If decoding pathWithinApp yields a match just use pathWithinApp.
      path = getRemainingPath(decodeInternal(request, pathWithinApp), servletPath, false);
      if (path != null) {
        return pathWithinApp;
      }
    }
    // Otherwise, use the full servlet path.
    return servletPath;
  }
}

根据注释即可看出在我们的场景中到 Spring MVC 去查询 handler 方法使用的 path 为 index.htm，导致匹配不到对应的 handler 方法。