Option for advanced ObjectMapper customization

Closes gh-23017

spring-web/src/main/java/org/springframework/http/converter/json/Jackson2ObjectMapperBuilder.java

@@ -26,6 +26,7 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.TimeZone;
+import java.util.function.Consumer;
 import java.util.function.Function;
 
 import com.fasterxml.jackson.annotation.JsonAutoDetect;
@@ -169,6 +170,9 @@ public class Jackson2ObjectMapperBuilder {
 	@Nullable
 	private Boolean defaultUseWrapper;
 
+	@Nullable
+	private Consumer<ObjectMapper> configurer;
+
 
 	/**
 	 * If set to {@code true}, an {@link XmlMapper} will be created using its
@@ -639,6 +643,19 @@ public class Jackson2ObjectMapperBuilder {
 		return this;
 	}
 
+	/**
+	 * An option to apply additional customizations directly to the
+	 * {@code ObjectMapper} instances at the end, after all other config
+	 * properties of the builder have been applied.
+	 * @param configurer a configurer to apply; if invoked multiple times, all
+	 * configurers are applied in the same order.
+	 * @since 5.3
+	 */
+	public Jackson2ObjectMapperBuilder postConfigurer(Consumer<ObjectMapper> configurer) {
+		this.configurer = (this.configurer != null ? this.configurer.andThen(configurer) : configurer);
+		return this;
+	}
+
 
 	/**
 	 * Build a new {@link ObjectMapper} instance.
@@ -740,6 +757,10 @@ public class Jackson2ObjectMapperBuilder {
 			objectMapper.setHandlerInstantiator(
 					new SpringHandlerInstantiator(this.applicationContext.getAutowireCapableBeanFactory()));
 		}
+
+		if (this.configurer != null) {
+			this.configurer.accept(objectMapper);
+		}
 	}
 
 	private void registerModule(Module module, MultiValueMap<Object, Module> modulesToRegister) {

spring-web/src/test/java/org/springframework/http/converter/json/Jackson2ObjectMapperBuilderTests.java

@@ -62,6 +62,7 @@ import com.fasterxml.jackson.databind.deser.BasicDeserializerFactory;
 import com.fasterxml.jackson.databind.deser.Deserializers;
 import com.fasterxml.jackson.databind.deser.std.DateDeserializers;
 import com.fasterxml.jackson.databind.introspect.AnnotationIntrospectorPair;
+import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector;
 import com.fasterxml.jackson.databind.introspect.NopAnnotationIntrospector;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.fasterxml.jackson.databind.module.SimpleSerializers;
@@ -431,6 +432,20 @@ public class Jackson2ObjectMapperBuilderTests {
 		assertThat(output).doesNotContain("value2");
 	}
 
+	@Test // gh-23017
+	public void postConfigurer() {
+
+		JacksonAnnotationIntrospector introspector1 = new JacksonAnnotationIntrospector();
+		JacksonAnnotationIntrospector introspector2 = new JacksonAnnotationIntrospector();
+
+		ObjectMapper mapper = Jackson2ObjectMapperBuilder.json()
+				.postConfigurer(m -> m.setAnnotationIntrospectors(introspector1, introspector2))
+				.build();
+
+		assertThat(mapper.getSerializationConfig().getAnnotationIntrospector()).isSameAs(introspector1);
+		assertThat(mapper.getDeserializationConfig().getAnnotationIntrospector()).isSameAs(introspector2);
+	}
+
 	@Test
 	public void completeSetup() throws JsonMappingException {
 		NopAnnotationIntrospector introspector = NopAnnotationIntrospector.instance;