private Class<?> injectClass0(ClassLoader classLoader, String className) throws IllegalArgumentException {
        if (isDebug) {
            logger.debug("Inject class className:{} cl:{}", className, classLoader);
        }
        final String pluginJarPath = pluginConfig.getPluginJarURLExternalForm();
        final ClassLoaderAttachment attachment = getClassLoaderAttachment(classLoader, pluginJarPath);
        final Class<?> findClazz = attachment.getClass(className);
        if (findClazz != null) {
            return findClazz;
        }

        if (logger.isInfoEnabled()) {
            logger.info("can not find class : {} {} ", className, pluginConfig.getPluginJarURLExternalForm());
        }
        // fallback
        return loadClass(classLoader, className);
    }
@author Woonduk Kang(emeroad)
@author jaehong.kim
agent-module/profiler/src/main/java/com/navercorp/pinpoint/profiler/instrument/classloading/PlainClassLoaderHandler.java