Process multipart properties for PartEvent support

Prior to this commit, some properties in the `spring.webflux.multipart`
namespace were ignored for the streaming use case because those were not
supported in streaming mode with `PartEvent`.

As of Spring Framework 6.1, the `max-parts` and
`max-disk-usage-per-part` properties can be supported and this commit
maps those properties accordingly.

Fixes gh-37642

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartAutoConfiguration.java

@@ -78,6 +78,10 @@ public class ReactiveMultipartAutoConfiguration {
 				map.from(multipartProperties::getMaxHeadersSize)
 					.asInt(DataSize::toBytes)
 					.to(partEventHttpMessageReader::setMaxHeadersSize);
+				map.from(multipartProperties::getMaxDiskUsagePerPart)
+					.as(DataSize::toBytes)
+					.to(partEventHttpMessageReader::setMaxPartSize);
+				map.from(multipartProperties::getMaxParts).to(partEventHttpMessageReader::setMaxParts);
 				map.from(multipartProperties::getHeadersCharset).to(partEventHttpMessageReader::setHeadersCharset);
 			}
 		});

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartProperties.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -37,7 +37,7 @@ public class ReactiveMultipartProperties {
 
 	/**
 	 * Maximum amount of memory allowed per part before it's written to disk. Set to -1 to
-	 * store all contents in memory. Ignored when streaming is enabled.
+	 * store all contents in memory.
 	 */
 	private DataSize maxInMemorySize = DataSize.ofKilobytes(256);
 
@@ -49,7 +49,7 @@ public class ReactiveMultipartProperties {
 
 	/**
 	 * Maximum amount of disk space allowed per part. Default is -1 which enforces no
-	 * limits. Ignored when streaming is enabled.
+	 * limits.
 	 */
 	private DataSize maxDiskUsagePerPart = DataSize.ofBytes(-1);
 
@@ -62,7 +62,7 @@ public class ReactiveMultipartProperties {
 	/**
 	 * Directory used to store file parts larger than 'maxInMemorySize'. Default is a
 	 * directory named 'spring-multipart' created under the system temporary directory.
-	 * Ignored when streaming is enabled.
+	 * Ignored when using the PartEvent streaming support.
 	 */
 	private String fileStorageDirectory;
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/ReactiveMultipartAutoConfigurationTests.java

@@ -84,17 +84,21 @@ class ReactiveMultipartAutoConfigurationTests {
 	void shouldConfigureMultipartPropertiesForPartEventReader() {
 		this.contextRunner
 			.withPropertyValues("spring.webflux.multipart.max-in-memory-size=1GB",
-					"spring.webflux.multipart.max-headers-size=16KB", "spring.webflux.multipart.headers-charset:UTF_16")
+					"spring.webflux.multipart.max-headers-size=16KB",
+					"spring.webflux.multipart.max-disk-usage-per-part=3GB", "spring.webflux.multipart.max-parts=7",
+					"spring.webflux.multipart.headers-charset:UTF_16")
 			.run((context) -> {
 				CodecCustomizer customizer = context.getBean(CodecCustomizer.class);
 				DefaultServerCodecConfigurer configurer = new DefaultServerCodecConfigurer();
 				customizer.customize(configurer);
 				PartEventHttpMessageReader partReader = getPartEventReader(configurer);
+				assertThat(partReader).hasFieldOrPropertyWithValue("maxParts", 7);
 				assertThat(partReader).hasFieldOrPropertyWithValue("maxHeadersSize",
 						Math.toIntExact(DataSize.ofKilobytes(16).toBytes()));
 				assertThat(partReader).hasFieldOrPropertyWithValue("headersCharset", StandardCharsets.UTF_16);
 				assertThat(partReader).hasFieldOrPropertyWithValue("maxInMemorySize",
 						Math.toIntExact(DataSize.ofGigabytes(1).toBytes()));
+				assertThat(partReader).hasFieldOrPropertyWithValue("maxPartSize", DataSize.ofGigabytes(3).toBytes());
 			});
 	}