public static Validator createRegexValidator()

in src/main/java/org/apache/nifi/processor/util/StandardValidators.java [672:716]
42 lines of code
5 McCabe index (conditional complexity)

    public static Validator createRegexValidator(final int minCapturingGroups, final int maxCapturingGroups, final boolean supportAttributeExpressionLanguage) {
        return new Validator() {
            @Override
            public ValidationResult validate(final String subject, final String value, final ValidationContext context) {
                try {
                    final String substituted;
                    if (supportAttributeExpressionLanguage) {
                        try {
                            substituted = context.newPropertyValue(value).evaluateAttributeExpressions().getValue();
                        } catch (final Exception e) {
                            return new ValidationResult.Builder()
                                    .subject(subject)
                                    .input(value)
                                    .valid(false)
                                .explanation("Failed to evaluate the Attribute Expression Language due to " + e)
                                    .build();
                        }
                    } else {
                        substituted = value;
                    }

                    final Pattern pattern = Pattern.compile(substituted);
                    final int numGroups = pattern.matcher("").groupCount();
                    if (numGroups < minCapturingGroups || numGroups > maxCapturingGroups) {
                        return new ValidationResult.Builder()
                                .subject(subject)
                                .input(value)
                                .valid(false)
                                .explanation("RegEx is required to have between " + minCapturingGroups + " and " + maxCapturingGroups + " Capturing Groups but has " + numGroups)
                                .build();
                    }

                    return new ValidationResult.Builder().subject(subject).input(value).valid(true).build();
                } catch (final Exception e) {
                    return new ValidationResult.Builder()
                            .subject(subject)
                            .input(value)
                            .valid(false)
                            .explanation("Not a valid Java Regular Expression")
                            .build();
                }

            }
        };
    }