public ValidationResult validate()

in src/main/java/org/apache/nifi/processor/util/StandardValidators.java [928:967]
35 lines of code
12 McCabe index (conditional complexity)

        public ValidationResult validate(final String subject, final String value, final ValidationContext context) {
            if (context.isExpressionLanguageSupported(subject) && context.isExpressionLanguagePresent(value)) {
                return new ValidationResult.Builder().subject(subject).input(value).explanation("Expression Language Present").valid(true).build();
            }

            final String substituted;
            if (allowEL) {
                try {
                    substituted = context.newPropertyValue(value).evaluateAttributeExpressions().getValue();
                } catch (final Exception e) {
                    return new ValidationResult.Builder().subject(subject).input(value).valid(false)
                            .explanation("Not a valid Expression Language value: " + e.getMessage()).build();
                }

                if (substituted.trim().isEmpty() && !value.trim().isEmpty()) {
                    // User specified an Expression and nothing more... assume valid.
                    return new ValidationResult.Builder().subject(subject).input(value).valid(true).build();
                }
            } else {
                substituted = value;
            }

            String reason = null;
            try {
                final File file = new File(substituted);
                if (!file.exists()) {
                    if (!create) {
                        reason = "Directory does not exist";
                    } else if (!file.mkdirs()) {
                        reason = "Directory does not exist and could not be created";
                    }
                } else if (!file.isDirectory()) {
                    reason = "Path does not point to a directory";
                }
            } catch (final Exception e) {
                reason = "Value is not a valid directory name";
            }

            return new ValidationResult.Builder().subject(subject).input(value).explanation(reason).valid(reason == null).build();
        }