I'm not sure if the problem you're having is with uima, but the regular expression you posted seems to be fine for me when working with plain java. I'm using java 1.7.0_45. I modified your regular expression just slightly to allow for multiple spaces around the number. Here is an SSCCE that when run the output is '445566553'
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexExample {
public static void main(String[] args) {
String test = "Numéro de réservation 445566553 \tCode";
Pattern pattern = Pattern.compile("(?<=Num\\u00E9ro\\sde\\sr\\u00E9servation)\\s+(.*?)\\s+(?=Code)");
Matcher matcher = pattern.matcher(test);
while(matcher.find()) {
System.out.println("'"+matcher.group(1)+"'");
}
}
}
If this isn't what you're looking for then providing an SSCCE that contains a test case you would like to fix would be helpful.