pkuwm commented on a change in pull request #1332:
URL: https://github.com/apache/helix/pull/1332#discussion_r480401890



##########
File path: 
zookeeper-api/src/main/java/org/apache/helix/zookeeper/zkclient/annotation/PreFetchChangedData.java
##########
@@ -22,8 +22,25 @@
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 
-
+/**
+ * An annotation used to prefetch changed data for
+ * {@link org.apache.helix.zookeeper.zkclient.IZkDataListener} in ZkClient.
+ * By default, prefetch is enabled: when ZkClient handles a data change event,
+ * ZkClient will read data and pass data object to
+ * {@link 
org.apache.helix.zookeeper.zkclient.IZkDataListener#handleDataChange(String, 
Object)}.
+ * If disabled({@code false}): ZkClient will not read data, so data object is 
passed as null.
+ * <p>
+ * Example:
+ * <pre>
+ * {@code @PreFetch(enabled = false)}
+ *  public class MyCallback implements IZkDataListener
+ * </pre>
+ *
+ * {@code @PreFetch(enabled = false)} means data will not be prefetched in 
ZkClient before
+ * handling data change: data is null in
+ * {@link 
org.apache.helix.zookeeper.zkclient.IZkDataListener#handleDataChange(String, 
Object)}
+ */
 @Retention(RetentionPolicy.RUNTIME)

Review comment:
       `Prefetch` is Helix's logic, should not be involved here in zkClient. 
The javadoc should stay in that interface, not this one.




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