Jackson YAML: mapping a regex Pattern with flags

Question

In Jackson, I can map a string in YAML:

regexField: "(\\d{2}):(\\d{2})"

to a Pattern field on a class:

final class MappedFromYaml {
    private Pattern regexField;
    // ... accessors
}

Jackson's ObjectMapper will create a Pattern with default flags. Is it possible to make it create it with specific flags set, such as Pattern.MULTILINE ? Ideally I would like to be able to specify those flags in YAML, but failing that a solution that specifies the flags for a specific field in Java code would also be appreciated.

Answer 1

There are two ways. The first is embedding flags directly into the regex :

regexField: "(\\d{2}):(\\d{2})(?m)"

Otherwise don't map directly to Pattern , but introduce a custom type like a PatternBuilder

public class PatternBuilder {
  public String regex;
  public boolean multiline;
  public Pattern pattern() {
    int flags = 0;
    if (multiline) flags |= Pattern.MULTILINE;
    return Pattern.compile(regex, flags);
  }
}

that can be built from the YAML

pattern:
  regex: "(\\d{2}):(\\d{2})"
  multiline: true