[LUCENE-1581] LowerCaseFilter should be able to be configured to use a specific locale.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Digy
• Created: 29/Mar/09 00:13
• Updated: 28/Aug/22 11:59
• Resolved: 01/Dec/09 20:41

Description

//Since I am a .Net programmer, Sample codes will be in c# but I don't think that it would be a problem to understand them.
//

Assume an input text like "İ" and and analyzer like below

	public class SomeAnalyzer : Analyzer
    	{
		public override TokenStream TokenStream(string fieldName, System.IO.TextReader reader)
	        {
            		TokenStream t = new SomeTokenizer(reader);
		        t = new Lucene.Net.Analysis.ASCIIFoldingFilter(t);
			t = new LowerCaseFilter(t);
		        return t;
		}
        
    	}

ASCIIFoldingFilter will return "I" and after, LowerCaseFilter will return
"i" (if locale is "en-US")
or
"ı' if(locale is "tr-TR") (that means,this token should be input to another instance of ASCIIFoldingFilter)

So, calling LowerCaseFilter before ASCIIFoldingFilter would be a solution, but a better approach can be adding
a new constructor to LowerCaseFilter and forcing it to use a specific locale.

    public sealed class LowerCaseFilter : TokenFilter
    {
        /* +++ */System.Globalization.CultureInfo CultureInfo = System.Globalization.CultureInfo.CurrentCulture;

        public LowerCaseFilter(TokenStream in) : base(in)
        {
        }

        /* +++ */  public LowerCaseFilter(TokenStream in, System.Globalization.CultureInfo CultureInfo) : base(in)
        /* +++ */  {
        /* +++ */      this.CultureInfo = CultureInfo;
        /* +++ */  }
		
        public override Token Next(Token result)
        {
            result = Input.Next(result);
            if (result != null)
            {

                char[] buffer = result.TermBuffer();
                int length = result.termLength;
                for (int i = 0; i < length; i++)
                    /* +++ */ buffer[i] = System.Char.ToLower(buffer[i],CultureInfo);

                return result;
            }
            else
                return null;
        }
    }

DIGY