Hi, I'm sorry for the earlier posts, my keyboard enter key was malfunctioning. I'm using weblogic 10, and deployed my application as EAR. My custom appender is located in the WEB-INF/lib. I am getting this ClassNotFoundException. app.ear - web1.war - WEB-INF/lib customAppenderPackage.jar So I've tried the following but still it can't find it: - deploying customAppenderPackage.jar as a shared library - putting in APP-INF/lib/customAppenderPackage.jar - adding in the MANIFEST Class-Path - adding as "library-ref" in weblogic.xml and weblogic-application.xml The only one that worked is when I moved the customAppenderPackage.jar in my weblogic server domain library directory. But I don't want this... I want it to be inside my EAR package. Any ideas how to solve this? How does class loading in logback works? Caused by: ch.qos.logback.core.util.DynamicClassLoadingException: Failed to instantiate type com.mycompany.CustomeAppender at at ch.qos.logback.core.util.OptionHelper.instantiateByClassName(OptionHelper.java:45) at at ch.qos.logback.core.util.OptionHelper.instantiateByClassName(OptionHelper.java:23) at at ch.qos.logback.core.joran.action.AppenderAction.begin(AppenderAction.java:50) at ... 51 common frames omitted Caused by: java.lang.ClassNotFoundException: com.mycompany.CustomeAppender at at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at at java.security.AccessController.doPrivileged(Native Method) at at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at at java.lang.ClassLoader.loadClass(ClassLoader.java:306)