Log4j SocketAppender. Logstash : tcp input --> OK, log4j input --> KO - SOLVED

Guess what... It works !
I used this tool to find the CordysLogger & Severity classes among the hundreds of jar files...
I found that the managementlib.jar file contains them and I have added the following entry in the log4j.rb file :

def register
    require "java"
    require "jruby/serialization"
    ################### ADDED LINE : ####################
    require "E:\\App\\ELK\\CordysLogger\\managementlib.jar"
    #####################################################

    begin
      Java::OrgApacheLog4jSpi.const_get("LoggingEvent")
    rescue
      raise(LogStash::PluginLoadingError, "Log4j java library not loaded")
    end

I am now correctly receiving and de-serializing the received objects.

Thank you wiibaa for your precious help on this topic !