spring boot send username in email html template

1@Bean 
2public FreeMarkerConfigurer freemarkerClassLoaderConfig() {
3    Configuration configuration = new Configuration(Configuration.VERSION_2_3_27);
4    TemplateLoader templateLoader = new ClassTemplateLoader(this.getClass(), "/mail-templates");
5    configuration.setTemplateLoader(templateLoader);
6    FreeMarkerConfigurer freeMarkerConfigurer = new FreeMarkerConfigurer();
7    freeMarkerConfigurer.setConfiguration(configuration);
8    return freeMarkerConfigurer; 
9}