Re: [logback-user] Joran and variable substitution

1 Jan 2011


      If all you are looking for is variable replacement then you could look at commons-lang's StrSubstitutor class.  Commons Configuration's ConfigurationInterpolator provides an example of how it can be used to resolve variables from multiple StrLookup sources, including SLF4J's MDCLookup. 

Ralph

On Dec 30, 2010, at 1:18 PM, Oliver Geishuettner wrote:
...
Thanks for the hint, this lead me in the right direction !
I found out that a simple context.subst in e.g. the begin part of the action is sufficient. To make things easier for me I created a small helper class:
public final class VariableHelper {
final static Logger log = LoggerFactory.getLogger(VariableHelper.class);
private InterpretationContext context = null;
private Attributes attrs = null;
private VariableHelper( InterpretationContext context, Attributes attrs ) {
 this.context = context;
 this.attrs = attrs;  
}
public static String replace(final InterpretationContext ic,
  final String str) {
 String ret = null;
 log.debug("before subst '{}'", str);
 ret = ic.subst(str);
 log.debug("after subst: '{}'", ret);
return ret;
}
public static String replace(final InterpretationContext ic,
  final Attributes attrs, final String attrName) {
 return replace(ic, attrs.getValue(attrName));
}
public String replace( String attrName ) {
 return replace( context, attrs, attrName );
}
public static VariableHelper createInstance( final InterpretationContext context, final Attributes attrs ) {
 return new VariableHelper( context, attrs );
}
}
This class can be used like this:
public class FooBarAction extends Action {
public void begin(InterpretationContext context, String arg1,
  Attributes attributes) throws ActionException {
 VariableHelper vh = VariableHelper.createInstance(context, attributes);
String foo = vh.replace("foo");
 String bar = vh.replace("sbar");
...
This is a replacement for:
String foo = attributes.getValue( "foo" );
foo = context.subst("foo" );
Perhaps this is of help for somebody.
-------- Original-Nachricht --------
...
Datum: Thu, 30 Dec 2010 13:35:37 +0100
Von: Ceki Gulcu <ceki@qos.ch>
An: logback users list <logback-user@qos.ch>
Betreff: Re: [logback-user] Joran and variable substitution
...
Hi Marge,
Variable substitution is done by Joran actions on an individual
basis. Search for usages of the subst() method of the
InterpretationContext class.
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Re: [logback-user] Joran and variable substitution

Ralph Goers