Add MediaType parameter to ApiVersionInserter

Closes gh-35259

spring-web/src/main/java/org/springframework/web/client/ApiVersionInserter.java

@@ -57,7 +57,7 @@ public interface ApiVersionInserter {
 	 * @param header the name of a header to hold the version
 	 */
 	static ApiVersionInserter useHeader(@Nullable String header) {
-		return new DefaultApiVersionInserterBuilder(header, null, null).build();
+		return new DefaultApiVersionInserterBuilder(header, null, null, null).build();
 	}
 
 	/**
@@ -65,7 +65,15 @@ public interface ApiVersionInserter {
 	 * @param queryParam the name of a query parameter to hold the version
 	 */
 	static ApiVersionInserter useQueryParam(@Nullable String queryParam) {
-		return new DefaultApiVersionInserterBuilder(null, queryParam, null).build();
+		return new DefaultApiVersionInserterBuilder(null, queryParam, null, null).build();
+	}
+
+	/**
+	 * Create an inserter to set a MediaType parameter on the "Content-Type" header.
+	 * @param mediaTypeParam the name of the media type parameter to hold the version
+	 */
+	static ApiVersionInserter useMediaTypeParam(@Nullable String mediaTypeParam) {
+		return new DefaultApiVersionInserterBuilder(null, null, mediaTypeParam, null).build();
 	}
 
 	/**
@@ -73,14 +81,14 @@ public interface ApiVersionInserter {
 	 * @param pathSegmentIndex the index of the path segment to hold the version
 	 */
 	static ApiVersionInserter usePathSegment(@Nullable Integer pathSegmentIndex) {
-		return new DefaultApiVersionInserterBuilder(null, null, pathSegmentIndex).build();
+		return new DefaultApiVersionInserterBuilder(null, null, null, pathSegmentIndex).build();
 	}
 
 	/**
 	 * Create a builder for an {@link ApiVersionInserter}.
 	 */
 	static Builder builder() {
-		return new DefaultApiVersionInserterBuilder(null, null, null);
+		return new DefaultApiVersionInserterBuilder(null, null, null, null);
 	}
 
 
@@ -101,6 +109,12 @@ public interface ApiVersionInserter {
 		 */
 		Builder useQueryParam(@Nullable String queryParam);
 
+		/**
+		 * Create an inserter to set a MediaType parameter on the "Content-Type" header.
+		 * @param param the name of the media type parameter to hold the version
+		 */
+		Builder useMediaTypeParam(@Nullable String param);
+
 		/**
 		 * Configure the inserter to insert a path segment.
 		 * @param pathSegmentIndex the index of the path segment to hold the version

spring-web/src/main/java/org/springframework/web/client/DefaultApiVersionInserter.java

@@ -18,11 +18,14 @@ package org.springframework.web.client;
 
 import java.net.URI;
 import java.util.ArrayList;
+import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
 
 import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
 import org.springframework.util.Assert;
 import org.springframework.web.util.UriComponentsBuilder;
 
@@ -39,20 +42,23 @@ final class DefaultApiVersionInserter implements ApiVersionInserter {
 
 	private final @Nullable String queryParam;
 
+	private final @Nullable String mediaTypeParam;
+
 	private final @Nullable Integer pathSegmentIndex;
 
 	private final ApiVersionFormatter versionFormatter;
 
 
 	DefaultApiVersionInserter(
-			@Nullable String header, @Nullable String queryParam, @Nullable Integer pathSegmentIndex,
-			@Nullable ApiVersionFormatter formatter) {
+			@Nullable String header, @Nullable String queryParam, @Nullable String mediaTypeParam,
+			@Nullable Integer pathSegmentIndex, @Nullable ApiVersionFormatter formatter) {
 
-		Assert.isTrue(header != null || queryParam != null || pathSegmentIndex != null,
-				"Expected 'header', 'queryParam', or 'pathSegmentIndex' to be configured");
+		Assert.isTrue(header != null || queryParam != null || mediaTypeParam != null || pathSegmentIndex != null,
+				"Expected 'header', 'queryParam', 'mediaTypeParam', or 'pathSegmentIndex' to be configured");
 
 		this.header = header;
 		this.queryParam = queryParam;
+		this.mediaTypeParam = mediaTypeParam;
 		this.pathSegmentIndex = pathSegmentIndex;
 		this.versionFormatter = (formatter != null ? formatter : Object::toString);
 	}
@@ -86,7 +92,17 @@ final class DefaultApiVersionInserter implements ApiVersionInserter {
 	@Override
 	public void insertVersion(Object version, HttpHeaders headers) {
 		if (this.header != null) {
-			headers.set(this.header, this.versionFormatter.formatVersion(version));
+			String formattedVersion = this.versionFormatter.formatVersion(version);
+			headers.set(this.header, formattedVersion);
+		}
+		if (this.mediaTypeParam != null) {
+			MediaType contentType = headers.getContentType();
+			if (contentType != null) {
+				Map<String, String> params = new LinkedHashMap<>(contentType.getParameters());
+				params.put(this.mediaTypeParam, this.versionFormatter.formatVersion(version));
+				contentType = new MediaType(contentType, params);
+				headers.setContentType(contentType);
+			}
 		}
 	}
 

spring-web/src/main/java/org/springframework/web/client/DefaultApiVersionInserterBuilder.java

@@ -33,16 +33,20 @@ final class DefaultApiVersionInserterBuilder implements ApiVersionInserter.Build
 
 	private @Nullable String queryParam;
 
+	private @Nullable String mediaTypeParam;
+
 	private @Nullable Integer pathSegmentIndex;
 
 	private @Nullable ApiVersionFormatter versionFormatter;
 
 
 	DefaultApiVersionInserterBuilder(
-			@Nullable String header, @Nullable String queryParam, @Nullable Integer pathSegmentIndex) {
+			@Nullable String header, @Nullable String queryParam, @Nullable String mediaTypeParam,
+			@Nullable Integer pathSegmentIndex) {
 
 		this.header = header;
 		this.queryParam = queryParam;
+		this.mediaTypeParam = mediaTypeParam;
 		this.pathSegmentIndex = pathSegmentIndex;
 	}
 
@@ -50,45 +54,40 @@ final class DefaultApiVersionInserterBuilder implements ApiVersionInserter.Build
 	 * Configure the inserter to set a header.
 	 * @param header the name of the header to hold the version
 	 */
+	@Override
 	public ApiVersionInserter.Builder useHeader(@Nullable String header) {
 		this.header = header;
 		return this;
 	}
 
-	/**
-	 * Configure the inserter to set a query parameter.
-	 * @param queryParam the name of the query parameter to hold the version
-	 */
+	@Override
 	public ApiVersionInserter.Builder useQueryParam(@Nullable String queryParam) {
 		this.queryParam = queryParam;
 		return this;
 	}
 
-	/**
-	 * Configure the inserter to insert a path segment.
-	 * @param pathSegmentIndex the index of the path segment to hold the version
-	 */
+	@Override
+	public ApiVersionInserter.Builder useMediaTypeParam(@Nullable String param) {
+		this.mediaTypeParam = param;
+		return this;
+	}
+
+	@Override
 	public ApiVersionInserter.Builder usePathSegment(@Nullable Integer pathSegmentIndex) {
 		this.pathSegmentIndex = pathSegmentIndex;
 		return this;
 	}
 
-	/**
-	 * Format the version Object into a String using the given {@link ApiVersionFormatter}.
-	 * <p>By default, the version is formatted with {@link Object#toString()}.
-	 * @param versionFormatter the formatter to use
-	 */
+	@Override
 	public ApiVersionInserter.Builder withVersionFormatter(ApiVersionFormatter versionFormatter) {
 		this.versionFormatter = versionFormatter;
 		return this;
 	}
 
-	/**
-	 * Build the inserter.
-	 */
 	public ApiVersionInserter build() {
 		return new DefaultApiVersionInserter(
-				this.header, this.queryParam, this.pathSegmentIndex, this.versionFormatter);
+				this.header, this.queryParam, this.mediaTypeParam, this.pathSegmentIndex,
+				this.versionFormatter);
 	}
 
 }

spring-web/src/test/java/org/springframework/web/client/RestClientVersionTests.java

@@ -26,6 +26,7 @@ import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.http.MediaType;
 import org.springframework.http.client.JdkClientHttpRequestFactory;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -73,6 +74,12 @@ public class RestClientVersionTests {
 		expectRequest(request -> assertThat(request.getTarget()).isEqualTo("/path?api-version=1.2"));
 	}
 
+	@Test
+	void mediaTypeParam() {
+		performRequest(ApiVersionInserter.useMediaTypeParam("v"));
+		expectRequest(request -> assertThat(request.getHeaders().get("Content-Type")).isEqualTo("application/json;v=1.2"));
+	}
+
 	@Test
 	void pathSegmentIndexLessThanSize() {
 		performRequest(ApiVersionInserter.builder().usePathSegment(0).withVersionFormatter(v -> "v" + v).build());
@@ -103,7 +110,8 @@ public class RestClientVersionTests {
 
 	private void performRequest(ApiVersionInserter versionInserter) {
 		restClientBuilder.apiVersionInserter(versionInserter).build()
-				.get().uri("/path")
+				.post().uri("/path")
+				.contentType(MediaType.APPLICATION_JSON)
 				.apiVersion(1.2)
 				.retrieve()
 				.body(String.class);