Currently trying, without success, to configure the AUTH-METHOD element of the web.xml externally (through system properties loaded during JBoss 7.1.1 startup).

I thought this would do the job : 

```
<login-config>
    <auth-method>${prest_authMethod}</auth-method>
    <realm-name>PREST Authentication</realm-name>
</login-config>

```

But it crashes during deployment : 

```
12:56:01,773 ERROR [org.apache.catalina.startup.ContextConfig] (MSC service thread 1-4) Cannot configure an authenticator for method ${prest_authMethod}

```

Is there a way to access system properties from web.xml ? Or any other way to configure the AUTH-METHOD with external configuration ?
Thanks for any help.