spring-projectsGH-1879: Factories Now Configure (De)Serializers

Resolves spring-projects#1879

It was not intuitive that configuration properties were not applied when
construcing (De)Serializers programmatically.

The producer and consumer factories now call the `configure()` method.
However, the JSON implementations cannot be configured with a mixture
of setters and configuration properties.

Author: garyrussell

spring-kafka-docs/src/main/asciidoc/kafka.adoc

@@ -529,6 +529,8 @@ void removeConfig(String configKey);
 ----
 ====
 
+Starting with version 2.8, if you provide serializers as objects (in the constructor or via the setters), the factory will invoke the `configure()` method to configure them with the configuration properties.
+
 [[replying-template]]
 ===== Using `ReplyingKafkaTemplate`
 
@@ -1133,6 +1135,8 @@ Defining `authorizationExceptionRetryInterval` should help the application to re
 
 NOTE: By default, no interval is configured - authorization errors are considered fatal, which causes the container to stop.
 
+Starting with version 2.8, when creating the consumer factory, if you provide deserializers as objects (in the constructor or via the setters), the factory will invoke the `configure()` method to configure them with the configuration properties.
+
 [[using-ConcurrentMessageListenerContainer]]
 ====== Using `ConcurrentMessageListenerContainer`
 
@@ -3943,6 +3947,9 @@ You can revert to the previous behavior by setting the `removeTypeHeaders` prope
 
 See also <<tip-json>>.
 
+IMPORTANT: Starting with version 2.8, if you construct the serializer or deserializer programmatically as shown in <<prog-json>>, the above properties will be applied by the factories, as long as you have not set any properties explicitly (using `set*()` methods or using the fluent API).
+Previously, when creating programmatically, the configuration properties were never applied; this is still the case if you explicitly set properties on the object directly.
+
 [[serdes-mapping-types]]
 ====== Mapping Types
 
@@ -4073,6 +4080,7 @@ public static JavaType thing1Thing2JavaTypeForTopic(String topic, byte[] data, H
 ----
 ====
 
+[[prog-json]]
 ====== Programmatic Construction
 
 When constructing the serializer/deserializer programmatically for use in the producer/consumer factory, since version 2.3, you can use the fluent API, which simplifies configuration.
@@ -4122,6 +4130,8 @@ JsonDeserializer<Object> deser = new JsonDeserializer<>()
 ----
 ====
 
+Alternatively, as long as you don't use the fluent API to configure properties, or set them using `set*()` methods, the factories will configure the serializer/deserializer using the configuration properties; see <<serdes-json-config>>.
+
 [[delegating-serialization]]
 ===== Delegating Serializer and Deserializer
 

spring-kafka/src/main/java/org/springframework/kafka/core/DefaultKafkaConsumerFactory.java

@@ -100,6 +100,8 @@ public DefaultKafkaConsumerFactory(Map<String, Object> configs) {
 
 	/**
 	 * Construct a factory with the provided configuration and deserializers.
+	 * The deserializers' {@code configure()} methods will be called with the
+	 * configuration map.
 	 * @param configs the configuration.
 	 * @param keyDeserializer the key {@link Deserializer}.
 	 * @param valueDeserializer the value {@link Deserializer}.
@@ -113,8 +115,10 @@ public DefaultKafkaConsumerFactory(Map<String, Object> configs,
 
 	/**
 	 * Construct a factory with the provided configuration and deserializer suppliers.
+	 * When the suppliers are invoked to get an instance, the deserializers'
+	 * {@code configure()} methods will be called with the configuration map.
 	 * @param configs the configuration.
-	 * @param keyDeserializerSupplier   the key {@link Deserializer} supplier function.
+	 * @param keyDeserializerSupplier the key {@link Deserializer} supplier function.
 	 * @param valueDeserializerSupplier the value {@link Deserializer} supplier function.
 	 * @since 2.3
 	 */
@@ -123,8 +127,32 @@ public DefaultKafkaConsumerFactory(Map<String, Object> configs,
 			@Nullable Supplier<Deserializer<V>> valueDeserializerSupplier) {
 
 		this.configs = new ConcurrentHashMap<>(configs);
-		this.keyDeserializerSupplier = keyDeserializerSupplier == null ? () -> null : keyDeserializerSupplier;
-		this.valueDeserializerSupplier = valueDeserializerSupplier == null ? () -> null : valueDeserializerSupplier;
+		this.keyDeserializerSupplier = keyDeserializerSupplier(keyDeserializerSupplier);
+		this.valueDeserializerSupplier = valueDeserializerSupplier(valueDeserializerSupplier);
+	}
+
+	private Supplier<Deserializer<K>> keyDeserializerSupplier(Supplier<Deserializer<K>> keyDeserializerSupplier) {
+		return keyDeserializerSupplier == null
+				? () -> null
+				: () -> {
+					Deserializer<K> deserializer = keyDeserializerSupplier.get();
+					if (deserializer != null) {
+						deserializer.configure(this.configs, true);
+					}
+					return deserializer;
+				};
+	}
+
+	private Supplier<Deserializer<V>> valueDeserializerSupplier(Supplier<Deserializer<V>> valueDeserializerSupplier) {
+		return valueDeserializerSupplier == null
+				? () -> null
+				: () -> {
+					Deserializer<V> deserializer = valueDeserializerSupplier.get();
+					if (deserializer != null) {
+						deserializer.configure(this.configs, false);
+					}
+					return deserializer;
+				};
 	}
 
 	@Override
@@ -137,15 +165,33 @@ public void setBeanName(String name) {
 	 * @param keyDeserializer the deserializer.
 	 */
 	public void setKeyDeserializer(@Nullable Deserializer<K> keyDeserializer) {
-		this.keyDeserializerSupplier = () -> keyDeserializer;
+		this.keyDeserializerSupplier = keyDeserializerSupplier(() -> keyDeserializer);
 	}
 
 	/**
 	 * Set the value deserializer.
 	 * @param valueDeserializer the valuee deserializer.
 	 */
 	public void setValueDeserializer(@Nullable Deserializer<V> valueDeserializer) {
-		this.valueDeserializerSupplier = () -> valueDeserializer;
+		this.valueDeserializerSupplier = valueDeserializerSupplier(() -> valueDeserializer);
+	}
+
+	/**
+	 * Set a supplier to supply instances of the key deserializer.
+	 * @param keyDeserializerSupplier the supplier.
+	 * @since 2.8
+	 */
+	public void setKeyDeserializerSupplier(Supplier<Deserializer<K>> keyDeserializerSupplier) {
+		this.keyDeserializerSupplier = keyDeserializerSupplier(keyDeserializerSupplier);
+	}
+
+	/**
+	 * Set a supplier to supply instances of the value deserializer.
+	 * @param valueDeserializerSupplier the supplier.
+	 * @since 2.8
+	 */
+	public void setValueDeserializerSupplier(Supplier<Deserializer<V>> valueDeserializerSupplier) {
+		this.valueDeserializerSupplier = valueDeserializerSupplier(valueDeserializerSupplier);
 	}
 
 	@Override

spring-kafka/src/main/java/org/springframework/kafka/core/DefaultKafkaProducerFactory.java

@@ -137,6 +137,10 @@ public class DefaultKafkaProducerFactory<K, V> extends KafkaResourceFactory
 
 	private Supplier<Serializer<V>> valueSerializerSupplier;
 
+	private Supplier<Serializer<K>> rawKeySerializerSupplier;
+
+	private Supplier<Serializer<V>> rawValueSerializerSupplier;
+
 	private Duration physicalCloseTimeout = DEFAULT_PHYSICAL_CLOSE_TIMEOUT;
 
 	private ApplicationContext applicationContext;
@@ -168,6 +172,8 @@ public DefaultKafkaProducerFactory(Map<String, Object> configs) {
 	 * Also configures a {@link #transactionIdPrefix} as a value from the
 	 * {@link ProducerConfig#TRANSACTIONAL_ID_CONFIG} if provided.
 	 * This config is going to be overridden with a suffix for target {@link Producer} instance.
+	 * The serializers' {@code configure()} methods will be called with the
+	 * configuration map.
 	 * @param configs the configuration.
 	 * @param keySerializer the key {@link Serializer}.
 	 * @param valueSerializer the value {@link Serializer}.
@@ -184,6 +190,8 @@ public DefaultKafkaProducerFactory(Map<String, Object> configs,
 	 * Also configures a {@link #transactionIdPrefix} as a value from the
 	 * {@link ProducerConfig#TRANSACTIONAL_ID_CONFIG} if provided.
 	 * This config is going to be overridden with a suffix for target {@link Producer} instance.
+	 * When the suppliers are invoked to get an instance, the serializers'
+	 * {@code configure()} methods will be called with the configuration map.
 	 * @param configs the configuration.
 	 * @param keySerializerSupplier the key {@link Serializer} supplier function.
 	 * @param valueSerializerSupplier the value {@link Serializer} supplier function.
@@ -194,12 +202,11 @@ public DefaultKafkaProducerFactory(Map<String, Object> configs,
 			@Nullable Supplier<Serializer<V>> valueSerializerSupplier) {
 
 		this.configs = new ConcurrentHashMap<>(configs);
-		this.keySerializerSupplier = keySerializerSupplier == null ? () -> null : keySerializerSupplier;
-		this.valueSerializerSupplier = valueSerializerSupplier == null ? () -> null : valueSerializerSupplier;
+		this.keySerializerSupplier = keySerializerSupplier(keySerializerSupplier);
+		this.valueSerializerSupplier = valueSerializerSupplier(valueSerializerSupplier);
 		if (this.clientIdPrefix == null && configs.get(ProducerConfig.CLIENT_ID_CONFIG) instanceof String) {
 			this.clientIdPrefix = (String) configs.get(ProducerConfig.CLIENT_ID_CONFIG);
 		}
-
 		String txId = (String) this.configs.get(ProducerConfig.TRANSACTIONAL_ID_CONFIG);
 		if (StringUtils.hasText(txId)) {
 			setTransactionIdPrefix(txId);
@@ -208,6 +215,32 @@ public DefaultKafkaProducerFactory(Map<String, Object> configs,
 		this.configs.put("internal.auto.downgrade.txn.commit", true);
 	}
 
+	private Supplier<Serializer<K>> keySerializerSupplier(Supplier<Serializer<K>> keySerializerSupplier) {
+		this.rawKeySerializerSupplier = keySerializerSupplier;
+		return keySerializerSupplier == null
+				? () -> null
+				: () -> {
+					Serializer<K> serializer = keySerializerSupplier.get();
+					if (serializer != null) {
+						serializer.configure(this.configs, true);
+					}
+					return serializer;
+				};
+	}
+
+	private Supplier<Serializer<V>> valueSerializerSupplier(Supplier<Serializer<V>> valueSerializerSupplier) {
+		this.rawValueSerializerSupplier = valueSerializerSupplier;
+		return valueSerializerSupplier == null
+				? () -> null
+				: () -> {
+					Serializer<V> serializer = valueSerializerSupplier.get();
+					if (serializer != null) {
+						serializer.configure(this.configs, false);
+					}
+					return serializer;
+				};
+	}
+
 	@Override
 	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
 		this.applicationContext = applicationContext;
@@ -223,15 +256,33 @@ public void setBeanName(String name) {
 	 * @param keySerializer the key serializer.
 	 */
 	public void setKeySerializer(@Nullable Serializer<K> keySerializer) {
-		this.keySerializerSupplier = () -> keySerializer;
+		this.keySerializerSupplier = keySerializerSupplier(() -> keySerializer);
 	}
 
 	/**
 	 * Set a value serializer.
 	 * @param valueSerializer the value serializer.
 	 */
 	public void setValueSerializer(@Nullable Serializer<V> valueSerializer) {
-		this.valueSerializerSupplier = () -> valueSerializer;
+		this.valueSerializerSupplier = valueSerializerSupplier(() -> valueSerializer);
+	}
+
+	/**
+	 * Set a supplier to supply instances of the key serializer.
+	 * @param keySerializerSupplier the supplier.
+	 * @since 2.8
+	 */
+	public void setKeySerializerSupplier(Supplier<Serializer<K>> keySerializerSupplier) {
+		this.keySerializerSupplier = keySerializerSupplier;
+	}
+
+	/**
+	 * Set a supplier to supply instances of the value serializer.
+	 * @param valueSerializerSupplier the supplier.
+	 * @since 2.8
+	 */
+	public void setValueSerializerSupplier(Supplier<Serializer<V>> valueSerializerSupplier) {
+		this.valueSerializerSupplier = valueSerializerSupplier;
 	}
 
 	/**
@@ -313,14 +364,27 @@ public boolean isProducerPerConsumerPartition() {
 		return this.producerPerConsumerPartition;
 	}
 
+
+	@Override
+	@Nullable
+	public Serializer<K> getKeySerializer() {
+		return this.keySerializerSupplier.get();
+	}
+
+	@Override
+	@Nullable
+	public Serializer<V> getValueSerializer() {
+		return this.valueSerializerSupplier.get();
+	}
+
 	@Override
 	public Supplier<Serializer<K>> getKeySerializerSupplier() {
-		return this.keySerializerSupplier;
+		return this.rawKeySerializerSupplier;
 	}
 
 	@Override
 	public Supplier<Serializer<V>> getValueSerializerSupplier() {
-		return this.valueSerializerSupplier;
+		return this.rawValueSerializerSupplier;
 	}
 
 	/**

spring-kafka/src/main/java/org/springframework/kafka/core/ProducerFactory.java

@@ -250,6 +250,29 @@ default void updateConfigs(Map<String, Object> updates) {
 	default void removeConfig(String configKey) {
 	}
 
+	/**
+	 * Return the configured key serializer (if provided as an object instead
+	 * of a class name in the properties).
+	 * @return the serializer.
+	 * @since 2.8
+	 */
+	@Nullable
+	default Serializer<K> getKeySerializer() {
+		return null;
+	}
+
+	/**
+	 * Return the configured value serializer (if provided as an object instead
+	 * of a class name in the properties).
+	 * @return the serializer.
+	 * @since 2.8
+	 */
+	@Nullable
+	default Serializer<V> getValueSerializer() {
+		return null;
+	}
+
+
 	/**
 	 * Called whenever a producer is added or removed.
 	 *

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019-2020 the original author or authors.
+ * Copyright 2019-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -83,6 +83,7 @@ public void configure(Map<String, ?> configs, boolean isKey) {
 			((Map<String, Object>) value).forEach((selector, deser) -> {
 				if (deser instanceof Deserializer) {
 					this.delegates.put(selector, (Deserializer<?>) deser);
+					((Deserializer<?>) deser).configure(configs, isKey);
 				}
 				else if (deser instanceof Class) {
 					instantiateAndConfigure(configs, isKey, this.delegates, selector, (Class<?>) deser);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019-2020 the original author or authors.
+ * Copyright 2019-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -108,6 +108,7 @@ else if (value instanceof Map) {
 			((Map<String, Object>) value).forEach((selector, serializer) -> {
 				if (serializer instanceof Serializer) {
 					this.delegates.put(selector, (Serializer<?>) serializer);
+					((Serializer<?>) serializer).configure(configs, isKey);
 				}
 				else if (serializer instanceof Class) {
 					instantiateAndConfigure(configs, isKey, this.delegates, selector, (Class<?>) serializer);