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

    Constructors
    Constructor and Description
    `WebAppRootListener()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `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`