## org.springframework.web.util
Class WebAppRootListener

    java.lang.Object
      org.springframework.web.util.WebAppRootListener

All Implemented Interfaces:
  EventListener, ServletContextListener

    public class WebAppRootListener

extends Object
implements ServletContextListener

Listener that sets a system property to the web application root directory. The key of the system property can be defined with the "webAppRootKey" init parameter at the servlet context level (i.e. context-param in web.xml), the default key is "webapp.root".

Can be used for toolkits that support substition with system properties (i.e. System.getProperty values), like log4j's "${key}" syntax within log file locations.

Note: This listener should be placed before ContextLoaderListener in `web.xml`, at least when used for log4j. Log4jConfigListener sets the system property implicitly, so there's no need for this listener in addition to it.

WARNING: Some containers, e.g. Tomcat, do NOT keep system properties separate per web app. You have to use unique "webAppRootKey" context-params per web app then, to avoid clashes. Other containers like Resin do isolate each web app's system properties: Here you can use the default key (i.e. no "webAppRootKey" context-param at all) without worrying.

WARNING: The WAR file containing the web application needs to be expanded to allow for setting the web app root system property. This is by default not the case when a WAR file gets deployed to WebLogic, for example. Do not use this listener in such an environment!

Since:
  18.04.2003
Author:
  Juergen Hoeller
See Also:
  `WebUtils.setWebAppRootSystemProperty(javax.servlet.ServletContext)`, `Log4jConfigListener`, `System.getProperty(java.lang.String)`

Constructor Summary
`WebAppRootListener()`

Method Summary
`void` `contextDestroyed(ServletContextEvent event)`
`void` `contextInitialized(ServletContextEvent event)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### WebAppRootListener

    public WebAppRootListener()

Method Detail

### contextInitialized

    public void contextInitialized(ServletContextEvent event)

  Specified by:
    `contextInitialized` in interface `ServletContextListener`

### contextDestroyed

    public void contextDestroyed(ServletContextEvent event)

  Specified by:
    `contextDestroyed` in interface `ServletContextListener`