[GitHub] [pulsar] yuruguo commented on a change in pull request #12961: [Broker] Fix NPE in `PersistentTopic.checkSubscriptionTypesEnable`

[GitBox <gi...@apache.org>]

yuruguo commented on a change in pull request #12961:
URL: https://github.com/apache/pulsar/pull/12961#discussion_r756174863



##########
File path: pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java
##########
@@ -3218,7 +3219,7 @@ public boolean checkSubscriptionTypesEnable(SubType subType) throws Exception {
                 if (topicPolicies == null) {
                     return checkNsAndBrokerSubscriptionTypesEnable(topicName, subType);
                 } else {
-                    if (topicPolicies.getSubscriptionTypesEnabled().isEmpty()) {
+                    if (CollectionUtils.isEmpty(topicPolicies.getSubscriptionTypesEnabled())) {

Review comment:
       `topicPolicies.getSubscriptionTypesEnabled()` default value is `empty list`, when can it become `null`?
   https://github.com/apache/pulsar/blob/94736a43f1b9a6d1db75936032b94eb9a11b9c0d/pulsar-common/src/main/java/org/apache/pulsar/common/policies/data/TopicPolicies.java#L47-L48
   In addition, it is recommended to combine the two judgments as below:
   ```
   if (topicPolicies == null || CollectionUtils.isEmpty(topicPolicies.getSubscriptionTypesEnabled())) {
       return checkNsAndBrokerSubscriptionTypesEnable(topicName, subType);
   } else {
       return topicPolicies.getSubscriptionTypesEnabled().contains(subType);
   }
   ```




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