public Converter newInternalConverter(boolean isKey, String className, Map<String, String> converterConfig) {
        Class<? extends Converter> klass;
        try {
            klass = pluginClass(delegatingLoader, className, Converter.class);
        } catch (ClassNotFoundException e) {
            throw new ConnectException("Failed to load internal converter class " + className);
        }

        Converter plugin;
        try (LoaderSwap loaderSwap = withClassLoader(klass.getClassLoader())) {
            plugin = newPlugin(klass);
            plugin.configure(converterConfig, isKey);
        }
        return plugin;
    }
Load an internal converter, used by the worker for (de)serializing data in internal topics.

@param isKey           whether the converter is a key converter
@param className       the class name of the converter
@param converterConfig the properties to configure the converter with
@return the instantiated and configured {@link Converter}; never null
@throws ConnectException if the {@link Converter} implementation class could not be found
connect/runtime/src/main/java/org/apache/kafka/connect/runtime/isolation/Plugins.java