WebApproot in Spring

Question

I get this error message

[ SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.util.Log4jConfigL

Answer 1

<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

Answer 2

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:

• Log4jWebConfigurer

Answer 3

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.

Answer 4

Just in case anyone else has done the above without getting rid of the problem:

Our webapp had the webAppRootKey set correctly, but I still got the exception above. Restarting Glassfish and redeploying the same war-file worked, go figure.

Answer 5

If you use logback instead of log4j and get the same error, this solves it:

<context-param>
 <param-name>logbackExposeWebAppRoot</param-name>
 <param-value>false</param-value>
</context-param>