pkuwm commented on a change in pull request #1332:
URL: https://github.com/apache/helix/pull/1332#discussion_r480384049
##########
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:
@kaisun2000 It tells the Java compiler and JVM that the annotation
should be available via reflection at runtime/class/source code. More details
you could check jdk javadoc.
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