←  filter.scala 

package ru.circumflex.web

import java.lang.reflect.InvocationTargetException
import javax.servlet._
import javax.servlet.http.{HttpServletResponse, HttpServletRequest}
import java.io._
import java.net.URLDecoder
import ru.circumflex.core._

Circumflex Filter

CircumflexFilter is an entry point of your web application. It handles context lifecycle (initializes context before the request is processed and finalizes context after the response is sent), serves static files and executes main request router.

To setup your web application place following snippet into your WEB-INF/web.xml:

<filter>
  <filter-name>Circumflex Filter</filter-name>
  <filter-class>ru.circumflex.web.CircumflexFilter</filter-class>
</filter>

<filter-mapping>
  <filter-name>Circumflex Filter</filter-name>
  <url-pattern>*</url-pattern>
</filter-mapping>

You can also include <dispatcher>REQUEST</dispatcher>, <dispatcher>FORWARD</dispatcher>, <dispatcher>INCLUDE</dispatcher> and <dispatcher>ERROR</dispatcher> under filter-mapping if your application requires so (for example, include ERROR dispatcher if you wish to serve error pages with Circumflex; beware of infinite loops, however).

The filter configuration is saved into the cx.filterConfig configuration parameter and is available throughout your configuration via the filterConfig method of the ru.circumflex.web package.

 
class CircumflexFilter extends Filter {

  def init(filterConfig: FilterConfig) = {
    WEB_LOG.info("Circumflex 2.0.1")
    cx("cx.filterConfig") = filterConfig
  }

  def destroy = {}

Serving static

Static files are images, stylesheets, javascripts and all other application assets which do not require special processing and can be served to clients “as is”.

By default static files are served from /public location of your webapp root, but you can specify different location by setting the cx.public configuration parameter.

 
  def serveStatic(req: HttpServletRequest,
                  res: HttpServletResponse,
                  chain: FilterChain): Boolean = {
    if (req.getMethod.equalsIgnoreCase("get") || req.getMethod.equalsIgnoreCase("head")) {
      val publicUri = cx.getOrElse("cx.public", "/public").toString
      val contextPath = servletContext.getContextPath
      if (req.getRequestURI.startsWith(contextPath + publicUri)) {
        chain.doFilter(req, res)
        return true
      }
      val relativeUri = req.getRequestURI.substring(contextPath.length)
      val uri = URLDecoder.decode(publicUri + relativeUri, "UTF-8")
      val path = filterConfig.getServletContext.getRealPath(uri)
      if (path == null) return false
      val resource = new File(path)
      if (resource.isFile) {
        req.getRequestDispatcher(uri).forward(req, res)
        return true
      }
    }
    return false
  }

Main Lifecycle

The lifecycle of CircumflexFilter involves following actions:

  1. try to serve static context and immediately exit on success;

  2. initialize Context and fill it with following variables:

    • cx.request will hold current HttpRequest;
    • cx.response will hold current HttpResponse;
    • cx.filterChain will hold current FilterChain;
    • other variables from prepareContext;
  3. the main router is instantiated (it's class should be specified via the cx.router configuration parameter;
  4. depending on the result of router's execution, either the response or the error is flushed to the client;
  5. the Context is destroyed.
 
  def doFilter(req: ServletRequest,
               res: ServletResponse,
               chain: FilterChain): Unit = (req, res) match {
    case (req: HttpServletRequest, res: HttpServletResponse) =>
      // try to serve static first
      if (serveStatic(req, res, chain)) return
      // initialize context
      Context.executeInNew { ctx =>
        ctx("cx.request") = new HttpRequest(req)
        ctx("cx.response") = new HttpResponse(res)
        ctx("cx.filterChain") = chain
        ctx("cx.locale") = req.getLocale
        prepareContext(ctx)
        try {
          WEB_LOG.trace(req)
          // execute main router
          try {
            cx.instantiate("cx.router") // ResponseSentException must be thrown
            onNoMatch()
          } catch {
            case e: InvocationTargetException => e.getCause match {
              case ex: ResponseSentException => throw ex
              case ex: FileNotFoundException => onNotFound(ex)
              case ex => onRouterError(ex)
            }
          }
        } catch {
          case e: ResponseSentException => WEB_LOG.trace(res)
        }
      }
    case _ =>
  }

The prepareContext method populates current context with various useful shortcuts (from web package):

  • param — the param object;
  • request — the request object;
  • session — the session object;
  • cookies — the cookies object;
  • headers — the headers object;
  • flash — the flash object;
  • cfg — the cx object;
  • msg — the msg object.

If you use custom filter implementation, you are can override this method to populate current context with global variables of your application.

 
  def prepareContext(ctx: Context): Unit = {
    'param := param
    'request := request
    'session := session
    'cookies := cookies
    'headers := headers
    'flash := flash
    'cfg := cx
    'msg := msg
  }

Callbacks

CircumflexFilter allows you to override following callbacks:

  • onNoMatch is executed if no routes match current request;
  • onNotFound is executed if a FileNotFoundException is thrown from a router;
  • onRouterError is executed if a general exception is thrown from a router;
 
  def onNoMatch(): Unit = {
    WEB_LOG.debug("No routes matched: " + request)
    sendError(404)
  }

  def onRouterError(e: Throwable): Unit = {
    WEB_LOG.error("Router threw an exception, see stack trace for details.", e)
    sendError(500)
  }

  def onNotFound(e: Throwable): Unit = {
    WEB_LOG.debug("Resource not found, see stack trace for details.", e)
    sendError(404)
  }

}