PluginClassLoader pluginClassLoader(String name) {
        if (!PluginUtils.shouldLoadInIsolation(name)) {
            return null;
        }
        SortedMap<PluginDesc<?>, ClassLoader> inner = pluginLoaders.get(name);
        if (inner == null) {
            return null;
        }
        ClassLoader pluginLoader = inner.get(inner.lastKey());
        return pluginLoader instanceof PluginClassLoader
               ? (PluginClassLoader) pluginLoader
               : null;
    }
Retrieve the PluginClassLoader associated with a plugin class
@param name The fully qualified class name of the plugin
@return the PluginClassLoader that should be used to load this, or null if the plugin is not isolated.
connect/runtime/src/main/java/org/apache/kafka/connect/runtime/isolation/DelegatingClassLoader.java