CodecConfigurer internal refactoring

Improve how HTTP message writers are obtained for general use vs for
multipart requests.

Author: rstoyanchev

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

@@ -134,6 +134,14 @@ private static List<MediaType> initMediaTypes(@Nullable HttpMessageWriter<?> for
 	}
 
 
+	/**
+	 * Return the configured part writers.
+	 * @since 5.0.7
+	 */
+	public List<HttpMessageWriter<?>> getPartWriters() {
+		return Collections.unmodifiableList(partWriters);
+	}
+
 	/**
 	 * Set the character set to use for part headers such as
 	 * "Content-Disposition" (and its filename parameter).

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

@@ -18,7 +18,6 @@
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.function.Supplier;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.Decoder;
@@ -28,6 +27,7 @@
 import org.springframework.http.codec.EncoderHttpMessageWriter;
 import org.springframework.http.codec.HttpMessageReader;
 import org.springframework.http.codec.HttpMessageWriter;
+import org.springframework.http.codec.multipart.MultipartHttpMessageWriter;
 import org.springframework.util.Assert;
 
 /**
@@ -85,30 +85,29 @@ public List<HttpMessageReader<?>> getReaders() {
 
 	@Override
 	public List<HttpMessageWriter<?>> getWriters() {
+		return getWritersInternal(false);
+	}
+
+	/**
+	 * Internal method that returns the configured writers.
+	 * @param forMultipart whether to returns writers for general use ("false"),
+	 * or for multipart requests only ("true"). Generally the two sets are the
+	 * same except for the multipart writer itself.
+	 */
+	protected List<HttpMessageWriter<?>> getWritersInternal(boolean forMultipart) {
 		List<HttpMessageWriter<?>> result = new ArrayList<>();
 
-		result.addAll(this.defaultCodecs.getTypedWriters());
+		result.addAll(this.defaultCodecs.getTypedWriters(forMultipart));
 		result.addAll(this.customCodecs.getTypedWriters());
 
-		result.addAll(this.defaultCodecs.getObjectWriters());
+		result.addAll(this.defaultCodecs.getObjectWriters(forMultipart));
 		result.addAll(this.customCodecs.getObjectWriters());
 
 		result.addAll(this.defaultCodecs.getCatchAllWriters());
 		return result;
 	}
 
 
-	// Accessors for use in sub-classes...
-
-	protected Supplier<List<HttpMessageWriter<?>>> getCustomTypedWriters() {
-		return () -> this.customCodecs.typedWriters;
-	}
-
-	protected Supplier<List<HttpMessageWriter<?>>> getCustomObjectWriters() {
-		return () -> this.customCodecs.objectWriters;
-	}
-
-
 	/**
 	 * Default implementation of {@code CustomCodecs}.
 	 */

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

@@ -95,8 +95,9 @@ void registerDefaults(boolean registerDefaults) {
 	}
 
 
-	// Package private access to the configured readers...
-
+	/**
+	 * Return readers that support specific types.
+	 */
 	final List<HttpMessageReader<?>> getTypedReaders() {
 		if (!this.registerDefaults) {
 			return Collections.emptyList();
@@ -112,9 +113,15 @@ final List<HttpMessageReader<?>> getTypedReaders() {
 		return readers;
 	}
 
+	/**
+	 * Hook for client or server specific typed readers.
+	 */
 	protected void extendTypedReaders(List<HttpMessageReader<?>> typedReaders) {
 	}
 
+	/**
+	 * Return Object readers (JSON, XML, SSE).
+	 */
 	final List<HttpMessageReader<?>> getObjectReaders() {
 		if (!this.registerDefaults) {
 			return Collections.emptyList();
@@ -133,9 +140,15 @@ final List<HttpMessageReader<?>> getObjectReaders() {
 		return readers;
 	}
 
+	/**
+	 * Hook for client or server specific Object readers.
+	 */
 	protected void extendObjectReaders(List<HttpMessageReader<?>> objectReaders) {
 	}
 
+	/**
+	 * Return readers that need to be at the end, after all others.
+	 */
 	final List<HttpMessageReader<?>> getCatchAllReaders() {
 		if (!this.registerDefaults) {
 			return Collections.emptyList();
@@ -145,10 +158,13 @@ final List<HttpMessageReader<?>> getCatchAllReaders() {
 		return result;
 	}
 
-
-	// Package private access to the configured writers...
-
-	final List<HttpMessageWriter<?>> getTypedWriters() {
+	/**
+	 * Return writers that support specific types.
+	 * @param forMultipart whether to returns writers for general use ("false"),
+	 * or for multipart requests only ("true"). Generally the two sets are the
+	 * same except for the multipart writer itself.
+	 */
+	final List<HttpMessageWriter<?>> getTypedWriters(boolean forMultipart) {
 		if (!this.registerDefaults) {
 			return Collections.emptyList();
 		}
@@ -158,14 +174,26 @@ final List<HttpMessageWriter<?>> getTypedWriters() {
 		writers.add(new EncoderHttpMessageWriter<>(new DataBufferEncoder()));
 		writers.add(new ResourceHttpMessageWriter());
 		writers.add(new EncoderHttpMessageWriter<>(CharSequenceEncoder.textPlainOnly()));
-		extendTypedWriters(writers);
+		// No client or server specific multipart writers currently..
+		if (!forMultipart) {
+			extendTypedWriters(writers);
+		}
 		return writers;
 	}
 
+	/**
+	 * Hook for client or server specific typed writers.
+	 */
 	protected void extendTypedWriters(List<HttpMessageWriter<?>> typedWriters) {
 	}
 
-	final List<HttpMessageWriter<?>> getObjectWriters() {
+	/**
+	 * Return Object writers (JSON, XML, SSE).
+	 * @param forMultipart whether to returns writers for general use ("false"),
+	 * or for multipart requests only ("true"). Generally the two sets are the
+	 * same except for the multipart writer itself.
+	 */
+	final List<HttpMessageWriter<?>> getObjectWriters(boolean forMultipart) {
 		if (!this.registerDefaults) {
 			return Collections.emptyList();
 		}
@@ -179,13 +207,22 @@ final List<HttpMessageWriter<?>> getObjectWriters() {
 		if (jaxb2Present) {
 			writers.add(new EncoderHttpMessageWriter<>(new Jaxb2XmlEncoder()));
 		}
-		extendObjectWriters(writers);
+		// No client or server specific multipart writers currently..
+		if (!forMultipart) {
+			extendObjectWriters(writers);
+		}
 		return writers;
 	}
 
+	/**
+	 * Hook for client or server specific Object writers.
+	 */
 	protected void extendObjectWriters(List<HttpMessageWriter<?>> objectWriters) {
 	}
 
+	/**
+	 * Return writers that need to be at the end, after all others.
+	 */
 	List<HttpMessageWriter<?>> getCatchAllWriters() {
 		if (!this.registerDefaults) {
 			return Collections.emptyList();

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

@@ -29,7 +29,6 @@
 import org.springframework.http.codec.ServerSentEventHttpMessageReader;
 import org.springframework.http.codec.multipart.MultipartHttpMessageWriter;
 import org.springframework.lang.Nullable;
-import org.springframework.util.Assert;
 
 /**
  * Default implementation of {@link ClientCodecConfigurer.ClientDefaultCodecs}.
@@ -45,18 +44,17 @@ class ClientDefaultCodecsImpl extends BaseDefaultCodecs implements ClientCodecCo
 	private Decoder<?> sseDecoder;
 
 	@Nullable
-	private Supplier<List<HttpMessageWriter<?>>> customTypedWriters;
+	private Supplier<List<HttpMessageWriter<?>>> partWritersSupplier;
 
-	@Nullable
-	private Supplier<List<HttpMessageWriter<?>>> customObjectWriters;
-
-
-	void initCustomTypedWriters(Supplier<List<HttpMessageWriter<?>>> supplier) {
-		this.customTypedWriters = supplier;
-	}
 
-	void initCustomObjectWriters(Supplier<List<HttpMessageWriter<?>>> supplier) {
-		this.customObjectWriters = supplier;
+	/**
+	 * Set a supplier for part writers to use when
+	 * {@link #multipartCodecs()} are not explicitly configured.
+	 * That's the same set of writers as for general except for the multipart
+	 * writer itself.
+	 */
+	void setPartWritersSupplier(Supplier<List<HttpMessageWriter<?>>> supplier) {
+		this.partWritersSupplier = supplier;
 	}
 
 
@@ -86,36 +84,19 @@ private Decoder<?> getSseDecoder() {
 
 	@Override
 	protected void extendTypedWriters(List<HttpMessageWriter<?>> typedWriters) {
-
-		MultipartHttpMessageWriter multipartWriter = new MultipartHttpMessageWriter(
-				resolvePartWriters(typedWriters, getObjectWriters()), new FormHttpMessageWriter());
-
-		typedWriters.add(multipartWriter);
+		typedWriters.add(new MultipartHttpMessageWriter(getPartWriters(), new FormHttpMessageWriter()));
 	}
 
-	private List<HttpMessageWriter<?>> resolvePartWriters(List<HttpMessageWriter<?>> typedWriters,
-			List<HttpMessageWriter<?>> objectWriters) {
-
-		List<HttpMessageWriter<?>> partWriters;
-		if (this.multipartCodecs != null) {
-			partWriters = this.multipartCodecs.getWriters();
-		}
-		else {
-			Assert.notNull(this.customTypedWriters, "Expected custom typed writers supplier.");
-			Assert.notNull(this.customObjectWriters, "Expected custom object writers supplier.");
-
-			partWriters = new ArrayList<>(typedWriters);
-			partWriters.addAll(this.customTypedWriters.get());
-
-			partWriters.addAll(objectWriters);
-			partWriters.addAll(this.customObjectWriters.get());
-
-			partWriters.addAll(super.getCatchAllWriters());
-		}
-		return partWriters;
+	@SuppressWarnings("ConstantConditions")
+	private List<HttpMessageWriter<?>> getPartWriters() {
+		return this.multipartCodecs != null ?
+				this.multipartCodecs.getWriters() : this.partWritersSupplier.get();
 	}
 
 
+	/**
+	 * Default implementation of {@link ClientCodecConfigurer.MultipartCodecs}.
+	 */
 	private static class DefaultMultipartCodecs implements ClientCodecConfigurer.MultipartCodecs {
 
 		private final List<HttpMessageWriter<?>> writers = new ArrayList<>();
@@ -137,4 +118,5 @@ List<HttpMessageWriter<?>> getWriters() {
 			return this.writers;
 		}
 	}
+
 }

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

@@ -29,8 +29,7 @@ public class DefaultClientCodecConfigurer extends BaseCodecConfigurer implements
 
 	public DefaultClientCodecConfigurer() {
 		super(new ClientDefaultCodecsImpl());
-		((ClientDefaultCodecsImpl) defaultCodecs()).initCustomTypedWriters(getCustomTypedWriters());
-		((ClientDefaultCodecsImpl) defaultCodecs()).initCustomObjectWriters(getCustomObjectWriters());
+		((ClientDefaultCodecsImpl) defaultCodecs()).setPartWritersSupplier(() -> getWritersInternal(true));
 	}