org.ehcache.jsr107.ConfigurationMerger.mergeConfigurations(String, Configuration<K, V>)
...
String templateName = jsr107Service.getTemplateNameForCache(cacheName);

org.ehcache.jsr107.internal.DefaultJsr107Service.getTemplateNameForCache(String cacheAlias) {
    final Jsr107Configuration cfg = configuration;
    if (cfg == null) {
      return null;
    }
    String template = cfg.getTemplates().get(cacheAlias);
    if (template != null) {
      return template;
    }
    return cfg.getDefaultTemplate();
}