public Class<ContentType> get(String contentTypeName) {
        final Class<ContentType> contentTypeClass = contentTypes.get(contentTypeName);
        if (contentTypeClass == null) {
            throw new RuntimeException("Content type with name " + contentTypeName + " not registered.");
        }
        return contentTypeClass;
    }
Content type handler class factory

@author <a href="mailto:wangyuxuan@dangdang.com">Yuxuan Wang</a>
config-toolkit/src/main/java/com/dangdang/config/service/file/contenttype/ContentTypes.java