String className = Appender.class.getName();
className = className.replace('.', '/');
String resource = "/" + className + ".class";
URL url = Appender.class.getResource(resource);
System.out.println(url.getFile());

//输出结果：

//file:/E:/JavaLib/log4j/log4j-1.2.14.jar!/org/apache/log4j/Appender.class