在java中将正则表达式模式替换为小写

Question

I'm trying to replace a url string to lowercase but wanted to keep the certain pattern string as it is.

eg: for input like:

http://BLABLABLA?qUERY=sth&macro1=${MACRO_STR1}&macro2=${macro_str2}

The expected output would be lowercased url but the multiple macros are original:

http://blablabla?query=sth&macro1=${MACRO_STR1}&macro2=${macro_str2}

I was trying to capture the strings using regex but didn't figure out a proper way to do the replacement. Also it seemed using replaceAll() doesn't do the job. Any hint please?

Answer 1

It looks like you want to change any uppercase character which is not inside ${...} to its lowercase form.

With construct

Matcher matcher = ...

StringBuffer buffer = new StringBuffer();
while (matcher.find()){
    String matchedPart = ...
    ...
    matcher.appendReplacement(buffer, replacement); 
}
matcher.appendTail(buffer);
String result = buffer.toString();

or since Java 9 we can use Matcher#replaceAll​(Function<MatchResult,String> replacer) and rewrite it like

String replaced = matcher.replaceAll(m -> {
    String matchedPart = m.group();
    ...
    return replacement;
});

you can dynamically build replacement based on matchedPart .

So you can let your regex first try to match ${...} and later (when ${..} will not be matched because regex cursor will not be placed before it) let it match [AZ] . While iterating over matches you can decide based on match result (like its length or if it starts with $ ) if you want to use use as replacement its lowercase form or original form.

BTW regex engine allows us to place in replacement part $x (where x is group id) or ${name} (where name is named group) so we could reuse those parts of match. But if we want to place ${..} as literal in replacement we need to escape \\$ . To not do it manually we can use Matcher.quoteReplacement .

Demo:

String yourUrlString = "http://BLABLABLA?qUERY=sth&macro1=${MACRO_STR1}&macro2=${macro_str2}";

Pattern p = Pattern.compile("\\$\\{[^}]+\\}|[A-Z]");
Matcher m = p.matcher(yourUrlString);

StringBuffer sb = new StringBuffer();
while(m.find()){
    String match = m.group();
    if (match.length() == 1){
        m.appendReplacement(sb, match.toLowerCase());
    } else {
        m.appendReplacement(sb, Matcher.quoteReplacement(match));
    }
}
m.appendTail(sb);
String replaced = sb.toString();
System.out.println(replaced);

or in Java 9

String replaced = Pattern.compile("\\$\\{[^}]+\\}|[A-Z]")
        .matcher(yourUrlString)
        .replaceAll(m -> {
            String match = m.group();
            if (match.length() == 1)
                return match.toLowerCase();
            else
                return Matcher.quoteReplacement(match); 
        });
System.out.println(replaced);

Output: http://blablabla?query=sth&macro1=${MACRO_STR1}&macro2=${macro_str2}

Answer 2

This regex will match all the characters before the first &macro , and put everything between http:// and the first &macro in its own group so you can modify it.

http://(.*?)&macro

Tested here

UPDATE: If you don't want to use groups, this regex will match only the characters between http:// and the first &macro

(?<=http://)(.*?)(?=&macro)

Tested here

Answer 3

As simple this need some coding . split whole url into parts till marcos and tolower the string 1 variable and append all other remaing macros string to it.