GH-4054: Fix missing Nullable in deserialize methods

Fixes #4054

Signed-off-by: Soby Chacko <[email protected]>

Author: sobychacko

spring-kafka/src/main/java/org/springframework/kafka/support/serializer/DelegatingByTopicDeserializer.java

@@ -22,6 +22,7 @@
 
 import org.apache.kafka.common.header.Headers;
 import org.apache.kafka.common.serialization.Deserializer;
+import org.jspecify.annotations.Nullable;
 
 /**
  * A {@link Deserializer} that delegates to other deserializers based on the topic name.
@@ -74,12 +75,12 @@ public Object deserialize(String topic, byte[] data) {
 	}
 
 	@Override
-	public Object deserialize(String topic, Headers headers, byte[] data) {
+	public @Nullable Object deserialize(String topic, Headers headers, byte[] data) {
 		return findDelegate(topic).deserialize(topic, headers, data);
 	}
 
 	@Override
-	public Object deserialize(String topic, Headers headers, ByteBuffer data) {
+	public @Nullable Object deserialize(String topic, Headers headers, ByteBuffer data) {
 		return findDelegate(topic).deserialize(topic, headers, data);
 	}
 

spring-kafka/src/main/java/org/springframework/kafka/support/serializer/DelegatingDeserializer.java

@@ -167,13 +167,13 @@ public Object deserialize(String topic, byte[] data) {
 	}
 
 	@Override
-	public Object deserialize(String topic, Headers headers, byte[] data) {
+	public @Nullable Object deserialize(String topic, Headers headers, byte[] data) {
 		Deserializer<?> deserializer = getDeserializerByHeaders(headers);
 		return deserializer == null ? data : deserializer.deserialize(topic, headers, data);
 	}
 
 	@Override
-	public Object deserialize(String topic, Headers headers, ByteBuffer data) {
+	public @Nullable Object deserialize(String topic, Headers headers, ByteBuffer data) {
 		Deserializer<?> deserializer = getDeserializerByHeaders(headers);
 		return deserializer == null ? data : deserializer.deserialize(topic, headers, data);
 	}

spring-kafka/src/main/java/org/springframework/kafka/support/serializer/RetryingDeserializer.java

@@ -68,17 +68,17 @@ public void configure(Map<String, ?> configs, boolean isKey) {
 	}
 
 	@Override
-	public T deserialize(String topic, byte[] data) {
+	public @Nullable T deserialize(String topic, byte[] data) {
 		return this.retryOperations.execute(context -> this.delegate.deserialize(topic, data), this.recoveryCallback);
 	}
 
 	@Override
-	public T deserialize(String topic, Headers headers, byte[] data) {
+	public @Nullable T deserialize(String topic, Headers headers, byte[] data) {
 		return this.retryOperations.execute(context -> this.delegate.deserialize(topic, headers, data), this.recoveryCallback);
 	}
 
 	@Override
-	public T deserialize(String topic, Headers headers, ByteBuffer data) {
+	public @Nullable T deserialize(String topic, Headers headers, ByteBuffer data) {
 		return this.retryOperations.execute(context -> this.delegate.deserialize(topic, headers, data), this.recoveryCallback);
 	}