Fix deprecation warnings caused by BodyInserters.fromObject

See gh-18349

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

@@ -143,7 +143,7 @@ public class DefaultErrorWebExceptionHandler extends AbstractErrorWebExceptionHa
 		boolean includeStackTrace = isIncludeStackTrace(request, MediaType.ALL);
 		Map<String, Object> error = getErrorAttributes(request, includeStackTrace);
 		return ServerResponse.status(getHttpStatus(error)).contentType(MediaType.APPLICATION_JSON)
-				.body(BodyInserters.fromObject(error));
+				.body(BodyInserters.fromValue(error));
 	}
 
 	/**

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/undertow/UndertowReactiveWebServerFactoryTests.java

@@ -118,7 +118,7 @@ class UndertowReactiveWebServerFactoryTests extends AbstractReactiveWebServerFac
 		this.webServer.start();
 		WebClient client = getWebClient().build();
 		Mono<String> result = client.post().uri("/test").contentType(MediaType.TEXT_PLAIN)
-				.body(BodyInserters.fromObject("Hello World")).exchange()
+				.body(BodyInserters.fromValue("Hello World")).exchange()
 				.flatMap((response) -> response.bodyToMono(String.class));
 		assertThat(result.block(Duration.ofSeconds(30))).isEqualTo("Hello World");
 		File accessLog = new File(accessLogDirectory, expectedFile);

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/reactive/server/AbstractReactiveWebServerFactoryTests.java

@@ -94,7 +94,7 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 		this.webServer = factory.getWebServer(new EchoHandler());
 		this.webServer.start();
 		Mono<String> result = getWebClient().build().post().uri("/test").contentType(MediaType.TEXT_PLAIN)
-				.body(BodyInserters.fromObject("Hello World")).exchange()
+				.body(BodyInserters.fromValue("Hello World")).exchange()
 				.flatMap((response) -> response.bodyToMono(String.class));
 		assertThat(result.block(Duration.ofSeconds(30))).isEqualTo("Hello World");
 		assertThat(this.webServer.getPort()).isEqualTo(specificPort);
@@ -122,7 +122,7 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 		WebClient client = WebClient.builder().baseUrl("https://localhost:" + this.webServer.getPort())
 				.clientConnector(connector).build();
 		Mono<String> result = client.post().uri("/test").contentType(MediaType.TEXT_PLAIN)
-				.body(BodyInserters.fromObject("Hello World")).exchange()
+				.body(BodyInserters.fromValue("Hello World")).exchange()
 				.flatMap((response) -> response.bodyToMono(String.class));
 		assertThat(result.block(Duration.ofSeconds(30))).isEqualTo("Hello World");
 	}
@@ -176,7 +176,7 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 		WebClient client = WebClient.builder().baseUrl("https://localhost:" + this.webServer.getPort())
 				.clientConnector(clientConnector).build();
 		Mono<String> result = client.post().uri("/test").contentType(MediaType.TEXT_PLAIN)
-				.body(BodyInserters.fromObject("Hello World")).exchange()
+				.body(BodyInserters.fromValue("Hello World")).exchange()
 				.flatMap((response) -> response.bodyToMono(String.class));
 		assertThat(result.block(Duration.ofSeconds(30))).isEqualTo("Hello World");
 	}
@@ -209,7 +209,7 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 		WebClient client = WebClient.builder().baseUrl("https://localhost:" + this.webServer.getPort())
 				.clientConnector(clientConnector).build();
 		Mono<String> result = client.post().uri("/test").contentType(MediaType.TEXT_PLAIN)
-				.body(BodyInserters.fromObject("Hello World")).exchange()
+				.body(BodyInserters.fromValue("Hello World")).exchange()
 				.flatMap((response) -> response.bodyToMono(String.class));
 		StepVerifier.create(result).expectError(SSLException.class).verify(Duration.ofSeconds(10));
 	}