Currently CustomAnalyzer only allows to specify the SPI names of factories. As the fluent builder pattern is mostly used inside Java code, it is better for type safety to optionally also specify the factory class directly (using compile-time safe patterns like .withTokenizer(WhitespaceTokenizerFactory.class)). With the string names, you get the error only at runtime. Of course this does not help with wrong, spelled parameter names, but it also has the side effect that you can click on the class name in your code to get javadocs with the parameter names.
This issue will add this functionality and update the docs/example.
Thanks to Shai Erera for suggesting this!