java - 如何使用 pattern tokenizer 仅索引在 lucene 中以大写字母开头的单词

Question

我正在使用 Lucene 5.1.0，我希望我的索引编写器仅索引以大写字母开头的术语。 我研究了自定义分析器和模式分词器，但我不明白如何使用它们来仅索引以大写字母开头的单词(或所有字母)。 任何帮助将不胜感激

Answer 1

我发现此链接有助于深入了解自定义分词器/分析器/过滤器: http://www.citrine.io/blog/2015/2/14/building-a-custom-analyzer-in-lucene

但是，在您的情况下，我认为扩展 org.apache.lucene.analysis.util.FilteringTokenFilter 而不是 TokenFilter 更容易:

public class StartsWithCapitalTokenFilter extends FilteringTokenFilter {

    private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);

    public StartsWithCapitalTokenFilter(TokenStream tokenStream) {
        super(tokenStream);
    }

    @Override
    public boolean accept() {
        // When accept() is called, my understanding is that termAtt.buffer() will
        // contain the particular string (in char[] form) of whichever token
        // is under consideration. This call gets the Unicode code point of the
        // first character and checks if it's uppercase.
        return Character.isUpperCase(Character.codePointAt(termAtt.buffer(),0));

        // Or if you don't want to care about Unicode about U+FFFF, use the below.
        //return Character.isUpperCase(termAtt.buffer()[0]);
    }
}

然后您将需要某种自定义分析器来使用过滤器。这个只使用新的过滤器:

public class StartswithCapitalAnalyzer extends Analyzer {
    @Override
    protected TokenStreamComponents createComponents(String field, Reader reader) {
        Tokenizer tokenizer = new StandardTokenizer();
        TokenStream filter = new StartsWithCapitalTokenFilter(tokenizer);

        // chain any other filters you want in here, like so:
        //filter = new LowerCaseFilter(filter);

        return new TokenStreamComponents(tokenizer, filter);
    }
}

虽然我现在没有测试它的环境，但它们应该都可以正常工作。 祝你好运!