Question

I need replace {word} by a regex named group: (?< word >\w++) to future match expressions, i.e.: /{name}/{age}… This code doesn’t work!

String p = "/{name}/{id}";
p = p.replaceAll("\\{(\\w+)\\}", "(?<$1>\\\\\\\\w+)");
Pattern URL_PATTERN = Pattern.compile(p);
CharSequence cs = "/lucas/3";
Matcher m = URL_PATTERN.matcher(cs);
if(m.matches()){
    for(int i=1;i<m.groupCount();++i){
        System.out.println(m.group("name"));
    }
}

Result: nothing 🙁

But when I get the result of replacement: /(?\w+)/(?\w+) and put in Pattern.compile() this works:

String p = "/{name}/{id}";
p = p.replaceAll("\\{(\\w+)\\}", "(?<$1>\\\\\\\\w+)");
Pattern URL_PATTERN = Pattern.compile("/(?<name>\\w+)/(?<id>\\w+)");
System.out.println(p);
CharSequence cs = "/lucas/3";
Matcher m = URL_PATTERN.matcher(cs);
if(m.matches()){
    for(int i=1;i<m.groupCount();++i){
        System.out.println(m.group("name"));
    }
}

Result: “lucas”

What’s wrong?

Answer 1

I think you used too many \ in your replace. Try

p = p.replaceAll("\\{(\\w+)\\}", "(?<$1>\\\\\\w+)");