如何在Lucene Analyzer上使用多个过滤器(Lucene 4.4)

Question

我正在尝试在我的自定义分析器中的TokenStream上应用多个过滤器.以下是代码:

public class CustomizeAnalyzer extends Analyzer {
//code omitted

@Override
protected TokenStreamComponents createComponents(String fieldName, Reader reader) {
    Tokenizer source = new LetterTokenizer(Version.LUCENE_44, reader);              
    TokenStream filter = new LowerCaseFilter(Version.LUCENE_44, source);                
    filter = new StopFilter(Version.LUCENE_44, filter, stopWords);                  
    return new TokenStreamComponents(source, new PorterStemFilter(source));
}                                              
}

但是,不会使用LowerCaseFilter.我真的按照这里的文档.有人可以解释一下如何让它发挥作用吗？

非常感谢,

Answer 1

你的问题在最后一行.你创建了一个过滤器链,然后通过传回来在return语句中将其短路new PorterStemFilter(source),这是一个直接位于标记器上的干式过滤器,而不是链中较早的过滤器.这应该是:

@Override
protected TokenStreamComponents createComponents(String fieldName, Reader reader) {
    Tokenizer source = new LetterTokenizer(Version.LUCENE_44, reader);              
    TokenStream filter = new LowerCaseFilter(Version.LUCENE_44, source);                
    filter = new StopFilter(Version.LUCENE_44, filter, stopWords);                  
    filter = new PorterStemFilter(filter);
    return new TokenStreamComponents(source, filter);
}