Re: Classloader problem

[Stephen McConnell]

What you need to do is to get Log interface into the initial classloader 
that is created by the jvm.  For the moment you will need to update the 
script that runs merlin (change -jar to -classpath, include a jar 
containing the Log interface, add the main cli jar, and include the Main 
class as a parameter).

I've been thinking about this question of customization of the initial 
classloader and I think we need a specific property containing a list of 
jars that should be loaded before loading merlin.  This could be added 
to the repository package so that the generated classloader chain would 
look like:

    SystemClassLoader
        ^
        |
    Common API ClassLoader <---- this would contain you Log interface
        ^
        |
    Repository Generated ClassLoader
Using this approach we guarantee that the supplementary API classes are 
in a parent classloader relative to both 'system' and 'application' 
classloaders.

Hope that helps.

Cheers, Stephen.



Maksimenko Alexander wrote:
Hi!
I try to describe my problem. I have to use instance of 
org.apache.commons.logging.Log in my components instead of Logger. So 
I've created my implementation of 
org.apache.avalon.logging.provider.LoggingManager. This implementation 
instantiates another LoggingManager implementation and wraps produced 
Logger instance. My wrapper implements both Logger and Log interfaces:

public class LogLogger implements Log, Logger{
  protected Logger logger = null;
  public LogLogger(Logger logger) {
    this.logger = logger;
  }
  public boolean isTraceEnabled() {
    return logger.isDebugEnabled();
  }
  public boolean isDebugEnabled() {
    return logger.isDebugEnabled();
  }
.....
}
So I can cast it to Log in my component:
  Log myLogger;
  public void enableLogging(Logger logger) {
    myLogger = (Log)logger;
  }
But unfortunately a get the following exception:

java.lang.ClassCastException
net.softwarium.commons.logger.avalon.TestComponent.enableLogging(TestComponent.java:47) 

org.apache.avalon.activation.appliance.impl.DefaultAppliance.applyLogger(DefaultAppliance.java:545) 

I discoved the cause of the exception is that Log class for 
LoggingManager and Log class for Component lay in distinct classloaders:

LoggingManager ClassLoader --->  Log ClassLoader ---> Merlin Impl 
ClassLoader --->.....
MyComponent ClassLoader ---> LogClassLoader ---> Merlin Impl ClassLoader 
--> ....

but I can't imagine how I can reapir this situation :(

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