Web Application Context Logging (log4j) Question

[sstacha]

I have been trying to implement a context listener that will allow me to have different repositories for each web application that is deployed. I was using several examples that I googled and keep getting java Verify errors. When tailoring it down line by line I finally got the following:


java.lang.LinkageError: loader constraints violated when linking org/apache/log4j/Level class
at org.apache.log4j.spi.WebAppRepositorySelector.init(WebAppRepositorySelector.java:36)
at biz.ormia.util.logging.ContextRepositoryListener.contextInitialized(ContextRepositoryListener.java:40


I intend to post more detailed code and such but I was wondering what is the appropriate forum to post this question to for the best response?

OS: OSX 10.5 (on intel mac)
jboss: 4.2.1 GA & 5.0.1 GA


Thanks,

steve

[jaikiran]

This is the right forum :)

Are you packaging any log4j jars with your application?

[sstacha]

Yes, I include log4j-1.2.8 in each webapp's WEB-INF/lib folder. Let me go ahead and post the background code and such then.

First, I was trying to load a context event listener with the following code:

package biz.ormia.util.logging;

/**
* User: sstacha
* Date: May 3, 2009
* Time: 1:22:11 PM
* Attempt to do logging without much effort on the devleopers part.
* Developers will need to add the following the web.xml file
*
* <listener-class>biz.ormia.util.logging.ContextRepositoryListener</listener-class>
*
*
*/

import org.apache.log4j.spi.WebAppRepositorySelector;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import java.util.Enumeration;

public class ContextRepositoryListener implements ServletContextListener
{
public void contextInitialized(ServletContextEvent contextEvent)
{
try
{
System.out.println("Attempting to add a context to the repositorySelector: " + contextEvent.getServletContext().getServletContextName());
Enumeration names=contextEvent.getServletContext().getAttributeNames();
System.out.println("----- attributes -----");
String name;
while (names.hasMoreElements())
{
name = (String)names.nextElement();
System.out.println(" " + name + " - " + contextEvent.getServletContext().getAttribute(name));
}
names=contextEvent.getServletContext().getInitParameterNames();
System.out.println("----- init params -----");
while (names.hasMoreElements())
System.out.println(" " + names.nextElement());
WebAppRepositorySelector.init(contextEvent.getServletContext());

//ContextRepositorySelector.init(contextEvent.getServletContext());

}
catch (Exception ex) {System.err.println(ex);}
}

public void contextDestroyed(ServletContextEvent contextEvent)
{
System.out.println("Attempting to remove a context from the repositorySelector: " + contextEvent.getServletContext());
ContextRepositorySelector.removeContext();
}
}


As you can see mostly I was trying to figure out what I had available to me and make sure it was being called. The only real thing in init is to call the
WebAppRepositorySelector.init(contextEvent.getServletContext());
WebAppRepositorySelector is my implementation which simply tries to take the default respository that jboss sets up and then tries to add a new one for each webapp deployment.

package org.apache.log4j.spi;

import org.apache.log4j.LogManager;
import org.apache.log4j.Hierarchy;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import java.util.Map;
import java.util.HashMap;

/**
* User: sstacha
* Date: May 5, 2009
* Time: 2:58:16 PM
* To change this template use File | Settings | File Templates.
*/
public class WebAppRepositorySelector implements RepositorySelector
{
private static Map<ClassLoader, LoggerRepository> repositories = new HashMap<ClassLoader, LoggerRepository>();
private static LoggerRepository defaultRepository;

public static void init(ServletContext context) throws ServletException
{
System.out.println("in addContext...");
System.out.println("current thread: " + Thread.currentThread().getName());
System.out.println("classloader: " + Thread.currentThread().getContextClassLoader().toString());
System.out.println("context: " + context.getServletContextName());
if (defaultRepository == null)
{
defaultRepository = LogManager.getLoggerRepository();
Object guard = LogManager.getRootLogger();
LogManager.setRepositorySelector(new WebAppRepositorySelector(), guard);
}
System.out.println("defaultRepository: " + defaultRepository.toString());

org.apache.log4j.Logger rootLogger = new RootLogger(org.apache.log4j.Level.DEBUG);
System.out.println("rootLogger: " + rootLogger);
// org.apache.log4j.Hierarchy hierarchy = new Hierarchy(rootLogger);
//
// try {repositories.put(Thread.currentThread().getContextClassLoader(), hierarchy);}
// catch (Exception ex) {System.out.println("Exception while creating new heiarchy for repository: " + ex);}
// if (defaultRepository == null)
// {
// defaultRepository = LogManager.getLoggerRepository();
// Object guard = LogManager.getRootLogger();
// LogManager.setRepositorySelector(new CTXRepositorySelector(), guard);
// }
// // add our thread instance in for lookup later
// Hierarchy hierarchy = new Hierarchy(new RootLogger(Level.DEBUG));
// try {repositories.put(Thread.currentThread().getContextClassLoader(), hierarchy);}
// catch (Exception ex) {System.out.println("Exception while creating new heiarchy for repository: " + ex);}
}

public static synchronized void removeContext()
{
System.out.println("in removeContext...");
System.out.println("current thread: " + Thread.currentThread().getName());
System.out.println("classloader: " + Thread.currentThread().getContextClassLoader().toString());
}


private WebAppRepositorySelector() { }

public LoggerRepository getLoggerRepository()
{
System.out.println("in getLoggerRepository...");
System.out.println("current thread: " + Thread.currentThread().getName());
System.out.println("classloader: " + Thread.currentThread().getContextClassLoader().toString());
ClassLoader cl = Thread.currentThread().getContextClassLoader();
// Hierarchy hierarchy = (Hierarchy) repositories.get(cl);
//
// if (hierarchy == null) {
// hierarchy = new Hierarchy(new RootLogger(org.apache.log4j.Level.DEBUG));
// hierMap.put(cl, hierarchy);
// }
//
// return hierarchy;
LoggerRepository repository = null;
try
{
repository = repositories.get(Thread.currentThread().getContextClassLoader());
}
catch (Exception ex) {System.out.println("Exception in getLoggerRepository getting the repository from the class loader: " + ex);}
if (repository == null)
{
System.out.println("respository is null using default...");
return defaultRepository;
}
else
{
System.out.println("Using repository: " + repository);
return repository;
}
// if (repository == null)
// return defaultRepository;
// return repository;
// if (defaultRepository != null)
// return defaultRepository;
// return null;
}
}


Note that this works as I have it commented here but I am not doing anything aside from saving off the original jboss repository and then resetting the selector to ourselves. If I uncomment the next line:

org.apache.log4j.Hierarchy hierarchy = new Hierarchy(rootLogger);

Then I get the error mentioned above. If I don't put my Selector in the log4j...spi package then I get a generic error:

[ERROR] - Exception sending context initialized event to listener instance of class biz.ormia.util.logging.ContextRepositoryListener
java.lang.VerifyError: (class: biz/ormia/util/logging/ContextRepositorySelector, method: init signature: (Ljavax/servlet/ServletContext;)V) Incompatible argument to function

[sstacha]

So, given the lack of responses... How are others dealing with having custom logging levels for multiple deployed applications?

Is there an easier way to pass a custom RepositorySelector via a parameter at startup or something?

[sstacha]

No one else has this problem or does custom logging for each application?