Provide default codecs config callback to custom codecs

As a follow-up of gh-23961, this change provides a way for custom codecs
to align with the default codecs' behavior on common features like
buffer size limits and logging request details.

Closes gh-24118
Co-authored-by: Rossen Stoyanchev <rstoyanchev@pivotal.io>

spring-web/src/main/java/org/springframework/http/codec/CodecConfigurer.java

@@ -17,9 +17,11 @@
 package org.springframework.http.codec;
 
 import java.util.List;
+import java.util.function.Consumer;
 
 import org.springframework.core.codec.Decoder;
 import org.springframework.core.codec.Encoder;
+import org.springframework.lang.Nullable;
 
 /**
  * Defines a common interface for configuring either client or server HTTP
@@ -212,6 +214,38 @@ interface CustomCodecs {
 		 * @param writer the writer to add
 		 */
 		void writer(HttpMessageWriter<?> writer);
+
+		/**
+		 * Register a callback for the {@link DefaultCodecConfig configuration}
+		 * applied to default codecs. This allows custom codecs to follow general
+		 * guidelines applied to default ones, such as logging details and limiting
+		 * the amount of buffered data.
+		 * @param codecsConfigConsumer the default codecs configuration callback
+		 * @since 5.1.12
+		 */
+		void withDefaultCodecConfig(Consumer<DefaultCodecConfig> codecsConfigConsumer);
+	}
+
+
+	/**
+	 * Common options applied to default codecs and passed in a callback to custom codecs
+	 * so they get a chance to align their behavior on the default ones.
+	 * @since 5.1.12
+	 */
+	interface DefaultCodecConfig {
+
+		/**
+		 * Get the configured limit on the number of bytes that can be buffered whenever
+		 * the input stream needs to be aggregated.
+		 */
+		@Nullable
+		Integer maxInMemorySize();
+
+		/**
+		 * Whether to log form data at DEBUG level, and headers at TRACE level.
+		 * Both may contain sensitive information.
+		 */
+		boolean isEnableLoggingRequestDetails();
 	}
 
 }

spring-web/src/main/java/org/springframework/http/codec/support/BaseCodecConfigurer.java

@@ -18,6 +18,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.function.Consumer;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.Decoder;
@@ -39,6 +40,8 @@
  */
 abstract class BaseCodecConfigurer implements CodecConfigurer {
 
+	protected boolean customCodecsInitialized;
+
 	protected final BaseDefaultCodecs defaultCodecs;
 
 	protected final DefaultCustomCodecs customCodecs;
@@ -88,6 +91,7 @@ public CustomCodecs customCodecs() {
 
 	@Override
 	public List<HttpMessageReader<?>> getReaders() {
+		initializeCustomCodecs();
 		List<HttpMessageReader<?>> result = new ArrayList<>();
 
 		result.addAll(this.customCodecs.getTypedReaders());
@@ -113,6 +117,7 @@ public List<HttpMessageWriter<?>> getWriters() {
 	 * same except for the multipart writer itself.
 	 */
 	protected List<HttpMessageWriter<?>> getWritersInternal(boolean forMultipart) {
+		initializeCustomCodecs();
 		List<HttpMessageWriter<?>> result = new ArrayList<>();
 
 		result.addAll(this.customCodecs.getTypedWriters());
@@ -128,6 +133,13 @@ protected List<HttpMessageWriter<?>> getWritersInternal(boolean forMultipart) {
 	@Override
 	public abstract CodecConfigurer clone();
 
+	private void initializeCustomCodecs() {
+		if(!this.customCodecsInitialized) {
+			this.customCodecs.configConsumers.forEach(consumer -> consumer.accept(this.defaultCodecs));
+			this.customCodecsInitialized = true;
+		}
+	}
+
 
 	/**
 	 * Default implementation of {@code CustomCodecs}.
@@ -142,6 +154,7 @@ protected static final class DefaultCustomCodecs implements CustomCodecs {
 
 		private final List<HttpMessageWriter<?>> objectWriters = new ArrayList<>();
 
+		private final List<Consumer<DefaultCodecConfig>> configConsumers = new ArrayList<>();
 
 		DefaultCustomCodecs() {
 		}
@@ -179,6 +192,11 @@ public void writer(HttpMessageWriter<?> writer) {
 			(canWriteObject ? this.objectWriters : this.typedWriters).add(writer);
 		}
 
+		@Override
+		public void withDefaultCodecConfig(Consumer<DefaultCodecConfig> codecsConfigConsumer) {
+			this.configConsumers.add(codecsConfigConsumer);
+		}
+
 		// Package private accessors...
 
 		List<HttpMessageReader<?>> getTypedReaders() {

spring-web/src/main/java/org/springframework/http/codec/support/BaseDefaultCodecs.java

@@ -60,7 +60,7 @@
  * @author Rossen Stoyanchev
  * @author Sebastien Deleuze
  */
-class BaseDefaultCodecs implements CodecConfigurer.DefaultCodecs {
+class BaseDefaultCodecs implements CodecConfigurer.DefaultCodecs, CodecConfigurer.DefaultCodecConfig {
 
 	static final boolean jackson2Present;
 
@@ -159,8 +159,9 @@ public void maxInMemorySize(int byteCount) {
 		this.maxInMemorySize = byteCount;
 	}
 
+	@Override
 	@Nullable
-	protected Integer maxInMemorySize() {
+	public Integer maxInMemorySize() {
 		return this.maxInMemorySize;
 	}
 
@@ -169,7 +170,8 @@ public void enableLoggingRequestDetails(boolean enable) {
 		this.enableLoggingRequestDetails = enable;
 	}
 
-	protected boolean isEnableLoggingRequestDetails() {
+	@Override
+	public boolean isEnableLoggingRequestDetails() {
 		return this.enableLoggingRequestDetails;
 	}
 

src/docs/asciidoc/web/webflux.adoc

@@ -950,7 +950,7 @@ The following example shows how to do so for client-side requests:
 			configurer.defaultCodecs().enableLoggingRequestDetails(true);
 
 	WebClient webClient = WebClient.builder()
-			.exchangeStrategies(ExchangeStrategies.builder().codecs(consumer).build())
+			.exchangeStrategies(strategies -> strategies.codecs(consumer))
 			.build();
 ----
 [source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
@@ -959,12 +959,53 @@ The following example shows how to do so for client-side requests:
 	val consumer: (ClientCodecConfigurer) -> Unit  = { configurer -> configurer.defaultCodecs().enableLoggingRequestDetails(true) }
 
 	val webClient = WebClient.builder()
-			.exchangeStrategies(ExchangeStrategies.builder().codecs(consumer).build())
+			.exchangeStrategies({ strategies -> strategies.codecs(consumer) })
 			.build()
 ----
 
+[[webflux-codecs-custom]]
+==== Custom codecs
 
+Applications can register custom codecs for supporting additional media types,
+or specific behaviors that are not supported by the default codecs.
 
+Some configuration options expressed by developers are enforced on default codecs.
+Custom codecs might want to get a chance to align with those preferences,
+like <<webflux-codecs-limits, enforcing buffering limits>>
+or <<webflux-logging-sensitive-data, logging sensitive data>>.
+
+The following example shows how to do so for client-side requests:
+
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
+.Java
+----
+	Consumer<ClientCodecConfigurer> consumer = configurer -> {
+	        CustomDecoder customDecoder = new CustomDecoder();
+	        configurer.customCodecs().decoder(customDecoder);
+			configurer.customCodecs().withDefaultCodecConfig(config ->
+				customDecoder.maxInMemorySize(config.maxInMemorySize())
+			);
+	}
+
+	WebClient webClient = WebClient.builder()
+			.exchangeStrategies(strategies -> strategies.codecs(consumer))
+			.build();
+----
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	val consumer: (ClientCodecConfigurer) -> Unit = { configurer ->
+			val customDecoder = CustomDecoder()
+			configurer.customCodecs().decoder(customDecoder)
+			configurer.customCodecs().withDefaultCodecConfig({ config ->
+				customDecoder.maxInMemorySize(config.maxInMemorySize())
+			})
+		}
+
+	val webClient = WebClient.builder()
+			.exchangeStrategies({ strategies -> strategies.codecs(consumer) })
+			.build()
+----
 
 [[webflux-dispatcher-handler]]
 == `DispatcherHandler`