[GitHub] [nifi] bbende commented on a change in pull request #3450: NIFI-1642 : Kafka Processors Topic Name Validations

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bbende commented on a change in pull request #3450: NIFI-1642 : Kafka Processors Topic Name Validations
URL: https://github.com/apache/nifi/pull/3450#discussion_r277371399
 
 

 ##########
 File path: nifi-nar-bundles/nifi-kafka-bundle/nifi-kafka-0-10-processors/src/main/java/org/apache/nifi/processors/kafka/pubsub/KafkaProcessorUtils.java
 ##########
 @@ -257,6 +288,54 @@
         return results;
     }
 
+
+    static final class KafkaConsumerTopicNameValidator implements Validator {
+
+        final Class<?> classType;
+
+        public KafkaConsumerTopicNameValidator(final Class<?> classType) {
+            this.classType = classType;
+        }
+
+        @Override
+        public ValidationResult validate(final String subject, final String value, final ValidationContext context) {
+            final String topicType = context.getProperty(CONSUMER_TOPIC_TYPE).evaluateAttributeExpressions().getValue();
+            final String topicListing = context.getProperty(CONSUMER_TOPICS).evaluateAttributeExpressions().getValue();
+            boolean isValidTopicName = true;
+            String topicName = "";
+            if (topicListing != null && topicType.equals(TOPIC_NAME.getValue())) {
+                for (final String topic : topicListing.split(",", 100)) {
+                    if(topic.isEmpty() || TOPIC_NAME_PATTERN.matcher(topic).replaceAll("").length() != 0 ) {
+                        isValidTopicName = false;
+                        topicName = topic;
+                    }
+                }
+            }
+            return new ValidationResult.Builder().subject(subject).explanation(topicName + " is not a valid topic name.").valid(isValidTopicName).build();
+        }
+    };
+
+    static final class KafkaProducerTopicNameValidator implements Validator {
+
+        final Class<?> classType;
+
+        public KafkaProducerTopicNameValidator(final Class<?> classType) {
+            this.classType = classType;
+        }
+
+        @Override
+        public ValidationResult validate(final String subject, final String value, final ValidationContext context) {
+            final String topicName = context.getProperty(PRODUCER_TOPIC).evaluateAttributeExpressions().getValue();
 
 Review comment:
   I'm not sure if we can validate the producer topic like this due to the fact that it supports EL from flow files. When EL from flow files is supported, flow files attributes are checked before variable registry. So there could be a variable name "kafka.topic" that is invalid, but at runtime the flow files have an attribute named kafka.topic that is valid, but you can't know that until the processor is running.

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