WebApproot in Spring
The webAppRootKey is a context parameter that Spring uses in a couple of places. In this case, it's being used by the Log4jWebConfigurer. It exposes the webapp root as a system property that can be used in log4j configuration files, something like this:
log4j.appender.testfile.File=${webapp.root}/WEB-INF/testlog.log You would use this if you, for some reason, wanted to locate your logs relative to your webapp root.
The problem that you're running into is that some containers (notably Tomcat) don't maintain a per-webapp mapping of system properties. When you don't specify a webAppRootKey, Spring defaults it to webapp.root. Since you're running two apps in the same container, the second app you're trying to start up sees that the webAppRootKey is already set (via the default), and throws an error. Otherwise, the webAppRootKey would be set incorrectly, and you could end up with logs from one webapp in another webapp.
You can specify a different webAppRootKey using context parameters in your web.xml like so:
<context-param> <param-name>webAppRootKey</param-name> <param-value>webapp.root.one</param-value></context-param>And
log4j.appender.testfile.File=${webapp.root.one}/WEB-INF/testlog.log in your log4j. This should take care of the conflict.
<context-param> <param-name>log4jExposeWebAppRoot</param-name> <param-value>false</param-value></context-param>...
This solved the problem for me. Credit to:-http://forum.springsource.org/archive/index.php/t-32873.html
It looks like you have several webapps with default Log4jConfigListener configuration in your application server.
Default behaviour for Log4jConfigurationListener is to expose webapp root as a system property named webapp.root, to allow you to use it when specifying log file locations. However, if system property with the same name already exists, it throws an exception.
You can either configure per-application names for that system property using <context-param> named webAppRootKey, or disable exposing of the system property by setting Log4jConfigListener's <init-param> named log4jExposeWebAppRoot to false.
See also: