tomcat_errorpage

scalatra 自定义404文件

在scalatra中，如果访问servlet不存在的路由时，默认为返回
Requesting "%s %s" on servlet "%s" but only have: %s

那么我就去源码看了看，发现如下代码：

protected var doNotFound: Action = () => {
    serveStaticResource() getOrElse resourceNotFound()
  }

  /**
   * Attempts to find a static resource matching the request path.  Override
   * to return None to stop this.
   */
  protected def serveStaticResource(): Option[Any] =
    servletContext.resource(request) map { _ =>
      servletContext.getNamedDispatcher("default").forward(request, response)
    }

  /**
   * Called by default notFound if no routes matched and no static resource
   * could be found.
   */
  protected def resourceNotFound(): Any = {
    response.setStatus(404)
    if (isDevelopmentMode) {
      val error = "Requesting \"%s %s\" on servlet \"%s\" but only have: %s"
      response.getWriter println error.format(
        request.getMethod,
        Option(request.getPathInfo) getOrElse "/",
        request.getServletPath,
        routes.entryPoints.mkString("<ul><li>", "</li><li>", "</li></ul>"))
    }
  }protected var doNotFound: Action = () => {
    serveStaticResource() getOrElse resourceNotFound()
  }

  /**
   * Attempts to find a static resource matching the request path.  Override
   * to return None to stop this.
   */
  protected def serveStaticResource(): Option[Any] =
    servletContext.resource(request) map { _ =>
      servletContext.getNamedDispatcher("default").forward(request, response)
    }

  /**
   * Called by default notFound if no routes matched and no static resource
   * could be found.
   */
  protected def resourceNotFound(): Any = {
    response.setStatus(404)
    if (isDevelopmentMode) {
      val error = "Requesting \"%s %s\" on servlet \"%s\" but only have: %s"
      response.getWriter println error.format(
        request.getMethod,
        Option(request.getPathInfo) getOrElse "/",
        request.getServletPath,
        routes.entryPoints.mkString("<ul><li>", "</li><li>", "</li></ul>"))
    }
  }

发现它如果没找到路由时，会尝试通过defaultServlet找静态资源，如果还找不到那么就会进入resourceNotFound方法，

如果是开发模式下，那么就会返回一开始提到的内容。。

如果我们通过在web.xml中配置：

<context-param>
        <param-name>org.scalatra.environment</param-name>
        <param-value>production</param-value>
    </context-param>

就不会显示配置的404页面，那是怎么回事呢？

我们来看看response.setStatus(404)

/**
     * Sets the status code for this response.
     *
     * <p>This method is used to set the return status code when there is
     * no error (for example, for the SC_OK or SC_MOVED_TEMPORARILY status
     * codes).
     *
     * <p>If this method is used to set an error code, then the container's
     * error page mechanism will not be triggered. If there is an error and
     * the caller wishes to invoke an error page defined in the web
     * application, then {@link #sendError} must be used instead.
     *
     * <p>This method preserves any cookies and other response headers.
     *
     * <p>Valid status codes are those in the 2XX, 3XX, 4XX, and 5XX ranges.
     * Other status codes are treated as container specific.
     *
     * @param	sc	the status code
     *
     * @see #sendError
     */
    public void setStatus(int sc);

有这么段话：
If this method is used to set an error code, then the container’s

error page mechanism（机制） will not be triggered.

参考资料：
Default Servlet
Tomcat use DefaultServlet for static content in external directory
Tomcat处理静态文件DefaultServlet分析
 Configuration
Configuring Web Application Components