Consider Jackson 2 in HTTP codec auto-config

See gh-47688

module/spring-boot-http-codec/build.gradle

@@ -31,6 +31,7 @@ dependencies {
 	optional(project(":core:spring-boot-autoconfigure"))
 	optional(project(":core:spring-boot-test"))
 	optional(project(":module:spring-boot-jackson"))
+	optional(project(":module:spring-boot-jackson2"))
 	optional("org.springframework:spring-webflux")
 
 	testImplementation(project(":core:spring-boot-test"))

module/spring-boot-http-codec/src/main/java/org/springframework/boot/http/codec/autoconfigure/CodecsAutoConfiguration.java

@@ -16,18 +16,22 @@
 
 package org.springframework.boot.http.codec.autoconfigure;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
 import org.jspecify.annotations.Nullable;
-import tools.jackson.databind.ObjectMapper;
 import tools.jackson.databind.json.JsonMapper;
 
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.AnyNestedCondition;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.context.properties.PropertyMapper;
 import org.springframework.boot.http.codec.CodecCustomizer;
 import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
@@ -43,14 +47,17 @@ import org.springframework.web.reactive.function.client.WebClient;
  * {@link org.springframework.core.codec.Decoder Decoders}.
  *
  * @author Brian Clozel
- * @since 2.0.0
+ * @since 4.0.0
  */
-@AutoConfiguration(afterName = "org.springframework.boot.jackson.autoconfigure.JacksonAutoConfiguration")
+@AutoConfiguration(afterName = { "org.springframework.boot.jackson.autoconfigure.JacksonAutoConfiguration",
+		"org.springframework.boot.jackson2.autoconfigure.Jackson2AutoConfiguration" })
 @ConditionalOnClass({ CodecConfigurer.class, WebClient.class })
 public final class CodecsAutoConfiguration {
 
 	@Configuration(proxyBeanMethods = false)
-	@ConditionalOnClass(ObjectMapper.class)
+	@ConditionalOnClass(JsonMapper.class)
+	@ConditionalOnProperty(name = "spring.http.codecs.preferred-json-mapper", havingValue = "jackson",
+			matchIfMissing = true)
 	static class JacksonJsonCodecConfiguration {
 
 		@Bean
@@ -66,6 +73,26 @@ public final class CodecsAutoConfiguration {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnClass(ObjectMapper.class)
+	@Conditional(NoJacksonOrJackson2Preferred.class)
+	@Deprecated(since = "4.0.0", forRemoval = true)
+	@SuppressWarnings("removal")
+	static class Jackson2JsonCodecConfiguration {
+
+		@Bean
+		@Order(0)
+		@ConditionalOnBean(ObjectMapper.class)
+		CodecCustomizer jackson2CodecCustomizer(ObjectMapper objectMapper) {
+			return (configurer) -> {
+				CodecConfigurer.DefaultCodecs defaults = configurer.defaultCodecs();
+				defaults.jacksonJsonDecoder(new org.springframework.http.codec.json.Jackson2JsonDecoder(objectMapper));
+				defaults.jacksonJsonEncoder(new org.springframework.http.codec.json.Jackson2JsonEncoder(objectMapper));
+			};
+		}
+
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	@EnableConfigurationProperties(HttpCodecsProperties.class)
 	static class DefaultCodecsConfiguration {
@@ -104,4 +131,22 @@ public final class CodecsAutoConfiguration {
 
 	}
 
+	static class NoJacksonOrJackson2Preferred extends AnyNestedCondition {
+
+		NoJacksonOrJackson2Preferred() {
+			super(ConfigurationPhase.PARSE_CONFIGURATION);
+		}
+
+		@ConditionalOnMissingClass("tools.jackson.databind.json.JsonMapper")
+		static class NoJackson {
+
+		}
+
+		@ConditionalOnProperty(name = "spring.http.codecs.preferred-json-mapper", havingValue = "jackson2")
+		static class Jackson2Preferred {
+
+		}
+
+	}
+
 }

module/spring-boot-http-codec/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -1,4 +1,28 @@
-{
-  "groups": [],
-  "properties": []
+{ 
+  "properties": [
+    {
+      "name": "spring.http.codecs.preferred-json-mapper",
+      "type": "java.lang.String",
+      "defaultValue": "jackson",
+      "description": "Preferred JSON mapper to use for HTTP encoding and decoding. By default, auto-detected according to the environment. Supported values are 'jackson' and 'jackson2' (deprecated)."
+    }
+  ],
+  "hints": [
+    {
+      "name": "spring.http.codecs.preferred-json-mapper",
+      "values": [
+        {
+          "value": "jackson"
+        },
+        {
+          "value": "jackson2"
+        }
+      ],
+      "providers": [
+        {
+          "name": "any"
+        }
+      ]
+    }
+  ]
 }

module/spring-boot-http-codec/src/test/java/org/springframework/boot/http/codec/autoconfigure/CodecsAutoConfigurationTests.java

@@ -18,11 +18,13 @@ package org.springframework.boot.http.codec.autoconfigure;
 
 import java.util.List;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
 import org.junit.jupiter.api.Test;
 import tools.jackson.databind.json.JsonMapper;
 
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.http.codec.CodecCustomizer;
+import org.springframework.boot.test.context.FilteredClassLoader;
 import org.springframework.boot.test.context.assertj.AssertableApplicationContext;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.context.annotation.Bean;
@@ -72,7 +74,7 @@ class CodecsAutoConfigurationTests {
 	}
 
 	@Test
-	void jacksonCodecCustomizerBacksOffWhenThereIsNoObjectMapper() {
+	void jacksonCodecCustomizerBacksOffWhenThereIsNoJsonMapper() {
 		this.contextRunner.run((context) -> assertThat(context).doesNotHaveBean("jacksonCodecCustomizer"));
 	}
 
@@ -82,6 +84,37 @@ class CodecsAutoConfigurationTests {
 			.run((context) -> assertThat(context).hasBean("jacksonCodecCustomizer"));
 	}
 
+	@Test
+	@Deprecated(since = "4.0.0", forRemoval = true)
+	void jacksonCodecCustomizerBacksOffWhenJackson2IsPreferred() {
+		this.contextRunner.withUserConfiguration(JsonMapperConfiguration.class)
+			.withPropertyValues("spring.http.codecs.preferred-json-mapper=jackson2")
+			.run((context) -> assertThat(context).doesNotHaveBean("jacksonCodecCustomizer"));
+	}
+
+	@Test
+	@Deprecated(since = "4.0.0", forRemoval = true)
+	void jackson2CodecCustomizerIsAutoConfiguredWhenObjectMapperIsPresentAndJackson2IsPreferred() {
+		this.contextRunner.withUserConfiguration(ObjectMapperConfiguration.class)
+			.withPropertyValues("spring.http.codecs.preferred-json-mapper=jackson2")
+			.run((context) -> assertThat(context).hasBean("jackson2CodecCustomizer"));
+	}
+
+	@Test
+	@Deprecated(since = "4.0.0", forRemoval = true)
+	void jackson2CodecCustomizerIsAutoConfiguredWhenObjectMapperIsPresentAndJacksonIsMissing() {
+		this.contextRunner.withUserConfiguration(ObjectMapperConfiguration.class)
+			.withClassLoader(new FilteredClassLoader(JsonMapper.class.getPackage().getName()))
+			.run((context) -> assertThat(context).hasBean("jackson2CodecCustomizer"));
+	}
+
+	@Test
+	@Deprecated(since = "4.0.0", forRemoval = true)
+	void jackson2CodecCustomizerBacksOffWhenJackson2IsPreferredButThereIsNoObjectMapper() {
+		this.contextRunner.withPropertyValues("spring.http.codecs.preferred-json-mapper=jackson2")
+			.run((context) -> assertThat(context).doesNotHaveBean("jackson2CodecCustomizer"));
+	}
+
 	@Test
 	void userProvidedCustomizerCanOverrideJacksonCodecCustomizer() {
 		this.contextRunner.withUserConfiguration(JsonMapperConfiguration.class, CodecCustomizerConfiguration.class)
@@ -116,6 +149,16 @@ class CodecsAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class ObjectMapperConfiguration {
+
+		@Bean
+		ObjectMapper objectMapper() {
+			return new ObjectMapper();
+		}
+
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class CodecCustomizerConfiguration {