ElLikeSubstitutionUtils.java

public class ElLikeSubstitutionUtils {

    private static final Pattern MATCH_PATTERN = Pattern.compile("\\$\\{([^}]+)\\}");

    /**
     * Replace ${name} with the appropriate template value retrieved from the map.
     * Does not gracefully handle nested or mismatched brace patterns
     */
    public static Verified<String> substitute(String string, Map<String, String> parameters) {
        List<SyndicationVerificationError> errors = Lists.newArrayList();
        Matcher m = MATCH_PATTERN.matcher(string);

        StringBuffer result = new StringBuffer();

        while (m.find()) {
            String parameterName = m.group(1);
            String replacement = parameters.get(parameterName);
            if (replacement == null) {
                replacement = "";
                errors.add(new SyndicationVerificationError("Parameter " + parameterName + " not present in map"));
            }
            m.appendReplacement(result, replacement);
        }
        m.appendTail(result);

        if (!errors.isEmpty()) {
            return new VerifiedFailure<String>(errors);
        }

        return new VerifiedSuccess<String>(result.toString());
    }
}