regex thoughts

RegexPractice.java

/*

Regex is interesting because I found out the following:
* It's pretty easy to translate patterns into actual variables.
* Even if you have repeated patterns, those can easily go into variables. (e.g: `(<some_pattern>)+` can be translated into an infinite number of variables)
* Some languages have a multiline mode that allow you to apply regex line-by-line. That has the benefit
of giving you more easily readable options.

To see a better example, look at the following code.

Java double backslashes can be annoying but the IDE coloring helps with that a lot.

 */
public class RegexPractice {
  @Test
  public void testThis() {
    System.out.println("test THIS start");
    String testString = "# HELP jetty_requests_total Number of requests\n" +
      "# TYPE jetty_requests_total counter\n" +
      "jetty_requests_total 0.0\n" +
      "# HELP jetty_requests_active Number of requests currently active\n" +
      "# TYPE jetty_requests_active gauge\n" +
      "jetty_requests_active 0.0\n" +
      "jetty_responses_total{code=\"1xx\",test=\"true\",} 0.0\n";

    Pattern regex = Pattern.compile("^(?!#)(\\w+)(\\{.*\\})? (\\d*\\.?\\d*)$", Pattern.MULTILINE);
    Matcher regexMatcher = regex.matcher(testString);
    while (regexMatcher.find()) {
      String metric = regexMatcher.group(1);
      String labels = regexMatcher.group(2);
      if(labels != null) {
        labels = labels.substring(1, labels.length() - 1); // Strip braces
        Pattern labelPattern = Pattern.compile("(\\p{Alnum}+)=\"(\\p{Alnum}+)\",");
        Matcher labelsMatcher = labelPattern.matcher(labels);
        while(labelsMatcher.find()) {
          System.out.println("label");
          System.out.println(labelsMatcher.group(1));
          System.out.println(labelsMatcher.group(2));
        }
      }
      String value = regexMatcher.group(3);
      System.out.println(metric);
      System.out.println(labels);
      System.out.println(value);
    }
    System.out.println("test THIS end");
  }

  @Test
  public void testLabels() {
    String labels = "code=\"hi\",blah=\"4xx\",";
    Pattern labelPattern = Pattern.compile("(\\p{Alnum}+)=\"(\\p{Alnum}+)\",");
    Matcher labelsMatcher = labelPattern.matcher(labels);
    while(labelsMatcher.find()) {
      System.out.println("label");
      System.out.println(labelsMatcher.group(1));
      System.out.println(labelsMatcher.group(2));
    }
  }
}

Context: This was for regex parsing on prometheus but you really don't need it in this case. Just learned a few useful points while using it.

I try to avoid regex unless it's necessary to make things easier because well, new developers and things.