Lucene 7.5.0 how to set lowercase expanded terms to true - lucene

Question

I have implemented my own Analyzer, QueryParser and PerFieldAnalyzerWrapper to implement the ElasticSearch ${field}.raw feature. Everything seems to be working ok, except for when I test using wildcards, etc on StringField types.
I understand this is because these queries don't use the analyzer at all.
In previous versions of lucene, there was a config option to enable the lowercasing of these queries.
I can't find how to do this in the latest version 7.5.0. Can anyone shed some light on this?

Answer 1

Expanded terms are processed by Analyzer.normalize. Since you have implemented your own Analyzer, add an implementation of the normalize method which runs the tokenStream through a LowerCaseFilter.
It can be as simple as:
public class MyAnalyzer extends Analyzer {
protected TokenStreamComponents createComponents(String fieldName) {
//Your createComponents implementation
}
protected TokenStream normalize(String fieldName, TokenStream in) {
return new LowerCaseFilter(in);
}
}

Answer 2

You can set up an analyzer like this for more details you can check out this link
Git link for CJK Bigram Plugin
#BeforeClass
public static void setUp() throws Exception {
analyzer = new Analyzer() {
#Override
protected TokenStreamComponents createComponents(String fieldName) {
Tokenizer source = new IcuTokenizer(AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY,
new DefaultIcuTokenizerConfig(false, true));
TokenStream result = new CJKBigramFilter(source);
return new TokenStreamComponents(source, new StopFilter(result, CharArraySet.EMPTY_SET));
}
};
analyzer2 = new Analyzer() {
#Override
protected TokenStreamComponents createComponents(String fieldName) {
Tokenizer source = new IcuTokenizer(AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY,
new DefaultIcuTokenizerConfig(false, true));
TokenStream result = new IcuNormalizerFilter(source,
Normalizer2.getInstance(null, "nfkc_cf", Normalizer2.Mode.COMPOSE));
result = new CJKBigramFilter(result);
return new TokenStreamComponents(source, new StopFilter(result, CharArraySet.EMPTY_SET));
}
};