Re: [logback-user] Context selectors useful?

27 Nov 2008

      Hello Lars,

You might want to check out logback 0.9.12-SNAPSHOT. It can be downloaded from

   http://logback.qos.ch/dist/logback-0.9.12-SNAPSHOT.tar.gz

I have tested logging separation in a Enterprise Application consisting of a 
stateless session and a web-app under JBoss 5.

In this version of logback, if you set up a env-entry for "logback/context-name" 
in JNDI, you no longer have to set an additional entry for the configuration 
file. For example, if "logback/context-name" is set to "MANGO", then the 
associated configuration file is named logback-MANGO.xml by convention. This 
makes things a bit easier, especially if you need to configure several EJBs or 
several web-apps.

The ejb-jar.xml file in my example reads

<?xml version="1.0"?>
<ejb-jar
  xmlns="http://java.sun.com/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd"
  version="3.0">

   <enterprise-beans>
     <session>
       <ejb-name>Echo</ejb-name>
       <env-entry>
         <description>JNDI logging context for this app</description>
         <env-entry-name>logback/context-name</env-entry-name>
         <env-entry-type>java.lang.String</env-entry-type>
         <env-entry-value>vader</env-entry-value>
       </env-entry>
     </session>
   </enterprise-beans>
</ejb-jar>

and web.xml reads

<web-app id="kenobi" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

   <display-name>kenobi</display-name>

   <servlet>
     <servlet-name>KenobiServlet</servlet-name>
     <servlet-class>ch.qos.KenobiServlet</servlet-class>
   </servlet>

   <servlet-mapping>
     <servlet-name>KenobiServlet</servlet-name>
     <url-pattern>/kenobi/*</url-pattern>
   </servlet-mapping>

   <env-entry>
     <description>JNDI logging context for this app</description>
     <env-entry-name>logback/context-name</env-entry-name>
     <env-entry-type>java.lang.String</env-entry-type>
     <env-entry-value>star</env-entry-value>
   </env-entry>

   <!-- To refer local EJB's  -->
   <ejb-local-ref>
     <ejb-ref-name>ejb/Echo</ejb-ref-name>
     <ejb-ref-type>Session</ejb-ref-type>
     <local-home></local-home>
     <local>ch.qos.IEcho</local>
   </ejb-local-ref>

</web-app>

While it was easy to get jndi context selector to work in JBoss, I was not able 
to make it work under Geronimo. Ironically, because it uses SLF4J internally.

HTH,

Lars Ködderitzsch wrote:
...
Hello Ceki,
thanks for the heads up on this issue on the mailing list.
Starting off I'd like to mention that for me the most wanted feature is
separation of logging from different contexts (e.g. war's, ejb) of of an
enterprise application (ear), without needing to resort to classloader
stunts, multiple repeated logging configurations etc.
That means that the contexts of an enterprise app should be able to use
the same logging implementation (that is placed in the ear classloader)
and the same logging configuration, but ultimately the log into
different log files.
This way it can be truely sorted out, which context logged which message.
To my knowledge such a thing is supported in neither logging
implementations.
Currently I am running this as a hack on log4j, based on a specialized
appender which switches the underlying log file based on some thread
local, which in turn is set by a special servlet filter in each web context.
At the time trying logback I thought that context selectors could
achieve that in a better, more standardized and less hacky way.
Ultimately I failed at the time and haven't looked back yet at logback.
So back to the question, yes, I would be very much interested in such a
feature - be it contexts selectors or something else.
If your're interested I can elaborate more on the problem, so you can
get a better understanding what would actually be needed.
Best regards,
Lars
Ceki Gulcu schrieb:
...
Hello all,
I am in the process of fixing bugs related to context selectors in logback. 
However, while sometime ago I thought that context selectors were the wave of 
the future, I am increasingly skeptical about their usefulness (of context 
selectors).
If you are using context selectors, could you please explain why?
-- 
Ceki Gülcü
Logback: The reliable, generic, fast and flexible logging framework for Java.
http://logback.qos.ch