[GitHub] [kafka] mjsax commented on a change in pull request #9000: KAFKA-10036 Improve handling and documentation of Suppliers

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

mjsax commented on a change in pull request #9000:
URL: https://github.com/apache/kafka/pull/9000#discussion_r516239935



##########
File path: streams/src/main/java/org/apache/kafka/streams/kstream/ValueTransformerSupplier.java
##########
@@ -33,12 +38,17 @@
  * @see TransformerSupplier
  * @see KStream#transform(TransformerSupplier, String...)
  */
-public interface ValueTransformerSupplier<V, VR> extends ConnectedStoreProvider {
+public interface ValueTransformerSupplier<V, VR> extends ConnectedStoreProvider, Supplier<ValueTransformer<V, VR>> {

Review comment:
       This seems to be a public API change that we cannot do without a KIP. Seem you added it so you can pass the different suppliers into `checkSupplier` ? Also not sure if `checkSupplier` must be as "complicated" as proposed.

##########
File path: streams/src/main/java/org/apache/kafka/streams/internals/ApiUtils.java
##########
@@ -75,4 +81,31 @@ public static long validateMillisecondInstant(final Instant instant, final Strin
     public static String prepareMillisCheckFailMsgPrefix(final Object value, final String name) {
         return format(MILLISECOND_VALIDATION_FAIL_MSG_FRMT, name, value);
     }
+
+    /**
+     * @throws IllegalArgumentException if the same instance is obtained each time
+     */
+    public static void checkSupplier(final Supplier<?> supplier) {
+        if (supplier.get() == supplier.get()) {
+            final String supplierClass = getAllImplementedInterfaces(supplier.getClass()).stream()

Review comment:
       Do we really need to try to extract the concrete interface name?




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