how to extract variables based on a pattern braces using regex in Java?

Question

Have this data input:

pattern: anyValue{variable1}otherValue{variable2}lastValue

value: anyValuehellootherValueworldlastValue

Expect this output

variable1: hello
variable2: world

can i have any variables with braces, I would like an example using Regex with an implementation in Java or another language,

Answer 1

You can use the following code in java:

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main {
    public static void main(String[] args) {
        String pattern= "anyvalue{variable1}anyvalue{variable2}anyvalue{var3}";
        String input = "anyvaluehelloanyvalueworldanyvaluesomething";

        // Convert the pattern into a regular expression
        String regex = pattern.replaceAll("\\{(.+?)\\}", "(?<$1>.*)");

        Pattern r = Pattern.compile(regex);
        Matcher m = r.matcher(input);
        
        if (m.find()) {
            // Get the names of the capture groups from the pattern
            Pattern groupNamesPattern = Pattern.compile("\\(\\?<(.+?)>");
            Matcher groupNamesMatcher = groupNamesPattern.matcher(regex);
            
            // Print all the variables that were found
            while (groupNamesMatcher.find()) {
                String variableName = groupNamesMatcher.group(1);
                String variableValue = m.group(variableName);
                System.out.println(variableName + ": " + variableValue);
            }
        } else {
            System.out.println("No match found.");
        }
    }
}

I am basically converting your pattern to named groups for any {variable_name} in the pattern. As far as I know, there is no easy way to get the groups' names, so you need a second regex to get those for your output.

However, there seem to be a few alternatives to find the named groups. You can follow this thread if you want to look into other alternatives to find the names of the groups.