Allow a custom JsonFactory to be used with JsonMapper.Builder

This commit improves the auto-configuration of the JSonMapper.Builder
to accept a custom JsonFactory if a bean of this type is present.

Closes gh-48594

documentation/spring-boot-docs/src/docs/antora/modules/how-to/pages/spring-mvc.adoc

@@ -106,7 +106,8 @@ This environment-based configuration is applied to the auto-configured javadoc:t
 
 To ease the migration when working on an application that previously used Jackson 2, the auto-configured `JsonMapper` can be configured to use defaults that are as close as possible to those that Spring Boot used for Jackson 2. To enable these defaults, set configprop:spring.jackson.use-jackson2-defaults[] to `true`.
 
-The context's javadoc:tools.jackson.databind.json.JsonMapper$Builder[] can be customized by one or more javadoc:org.springframework.boot.jackson.autoconfigure.JsonMapperBuilderCustomizer[] beans.
+If a javadoc:tools.jackson.core.json.JsonFactory[] bean is present, it is used by the context's javadoc:tools.jackson.databind.json.JsonMapper$Builder[].
+The builder can also be customized by one or more javadoc:org.springframework.boot.jackson.autoconfigure.JsonMapperBuilderCustomizer[] beans.
 Such customizer beans can be ordered (Boot's own customizer has an order of 0), letting additional customization be applied both before and after Boot's customization.
 
 Any beans of type javadoc:tools.jackson.databind.JacksonModule[] are automatically registered with the auto-configured javadoc:tools.jackson.databind.json.JsonMapper$Builder[] and are applied to any javadoc:tools.jackson.databind.json.JsonMapper[] instances that it creates.

module/spring-boot-jackson/src/main/java/org/springframework/boot/jackson/autoconfigure/JacksonAutoConfiguration.java

@@ -32,6 +32,7 @@ import com.fasterxml.jackson.annotation.JsonAutoDetect;
 import com.fasterxml.jackson.annotation.JsonInclude.Include;
 import com.fasterxml.jackson.annotation.PropertyAccessor;
 import org.jspecify.annotations.Nullable;
+import tools.jackson.core.json.JsonFactory;
 import tools.jackson.databind.JacksonModule;
 import tools.jackson.databind.ObjectMapper;
 import tools.jackson.databind.PropertyNamingStrategies;
@@ -97,8 +98,9 @@ public final class JacksonAutoConfiguration {
 	@Bean
 	@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
 	@ConditionalOnMissingBean
-	JsonMapper.Builder jsonMapperBuilder(List<JsonMapperBuilderCustomizer> customizers) {
-		JsonMapper.Builder builder = JsonMapper.builder();
+	JsonMapper.Builder jsonMapperBuilder(ObjectProvider<JsonFactory> jsonFactory,
+			List<JsonMapperBuilderCustomizer> customizers) {
+		JsonMapper.Builder builder = JsonMapper.builder(jsonFactory.getIfAvailable(JsonFactory::new));
 		customize(builder, customizers);
 		return builder;
 	}

module/spring-boot-jackson/src/test/java/org/springframework/boot/jackson/autoconfigure/JacksonAutoConfigurationTests.java

@@ -34,6 +34,8 @@ import org.junit.jupiter.params.provider.EnumSource;
 import tools.jackson.core.JsonGenerator;
 import tools.jackson.core.StreamReadFeature;
 import tools.jackson.core.StreamWriteFeature;
+import tools.jackson.core.json.JsonFactory;
+import tools.jackson.core.json.JsonFactoryBuilder;
 import tools.jackson.core.json.JsonReadFeature;
 import tools.jackson.core.json.JsonWriteFeature;
 import tools.jackson.databind.DeserializationFeature;
@@ -391,6 +393,24 @@ class JacksonAutoConfigurationTests {
 			});
 	}
 
+	@Test
+	void defaultJsonFactoryIsRegisteredWithTheMapperBuilderWhenNoCustomFactoryExists() {
+		this.contextRunner.run((context) -> {
+			Builder jsonMapperBuilder = context.getBean(JsonMapper.Builder.class);
+			assertThat(jsonMapperBuilder.isEnabled(StreamReadFeature.AUTO_CLOSE_SOURCE)).isTrue();
+		});
+	}
+
+	@Test
+	void customJsonFactoryIsRegisteredWithTheMapperBuilder() {
+		JsonFactory customJsonFactory = new JsonFactoryBuilder().configure(StreamReadFeature.AUTO_CLOSE_SOURCE, false)
+			.build();
+		this.contextRunner.withBean("customJsonFactory", JsonFactory.class, () -> customJsonFactory).run((context) -> {
+			Builder jsonMapperBuilder = context.getBean(JsonMapper.Builder.class);
+			assertThat(jsonMapperBuilder.isEnabled(StreamReadFeature.AUTO_CLOSE_SOURCE)).isFalse();
+		});
+	}
+
 	@EnumSource
 	@ParameterizedTest
 	void moduleBeansAndWellKnownModulesAreRegisteredWithTheMapperBuilder(MapperType mapperType) {