Option to pair AnnotationIntrospector instances

Closes gh-22830

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,6 +26,7 @@
 import java.util.Locale;
 import java.util.Map;
 import java.util.TimeZone;
+import java.util.function.Function;
 
 import com.fasterxml.jackson.annotation.JsonAutoDetect;
 import com.fasterxml.jackson.annotation.JsonFilter;
@@ -45,6 +46,7 @@
 import com.fasterxml.jackson.databind.PropertyNamingStrategy;
 import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.databind.cfg.HandlerInstantiator;
+import com.fasterxml.jackson.databind.introspect.AnnotationIntrospectorPair;
 import com.fasterxml.jackson.databind.jsontype.TypeResolverBuilder;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.fasterxml.jackson.databind.ser.FilterProvider;
@@ -260,6 +262,23 @@ public Jackson2ObjectMapperBuilder annotationIntrospector(AnnotationIntrospector
 		return this;
 	}
 
+	/**
+	 * Alternative to {@link #annotationIntrospector(AnnotationIntrospector)}
+	 * that allows combining with rather than replacing the currently set
+	 * introspector, e.g. via
+	 * {@link AnnotationIntrospectorPair#pair(AnnotationIntrospector, AnnotationIntrospector)}.
+	 * @param pairingFunction a function to apply to the currently set
+	 * introspector (possibly {@code null}); the result of the function becomes
+	 * the new introspector.
+	 * @since 5.2.4
+	 */
+	public Jackson2ObjectMapperBuilder annotationIntrospector(
+			Function<AnnotationIntrospector, AnnotationIntrospector> pairingFunction) {
+
+		this.annotationIntrospector = pairingFunction.apply(this.annotationIntrospector);
+		return this;
+	}
+
 	/**
 	 * Specify a {@link com.fasterxml.jackson.databind.PropertyNamingStrategy} to
 	 * configure the {@link ObjectMapper} with.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -43,6 +43,7 @@
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.core.Version;
+import com.fasterxml.jackson.databind.AnnotationIntrospector;
 import com.fasterxml.jackson.databind.DeserializationContext;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.JsonDeserializer;
@@ -60,6 +61,7 @@
 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.NopAnnotationIntrospector;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.fasterxml.jackson.databind.module.SimpleSerializers;
@@ -431,7 +433,7 @@ public void filters() throws JsonProcessingException {
 
 	@Test
 	public void completeSetup() throws JsonMappingException {
-		NopAnnotationIntrospector annotationIntrospector = NopAnnotationIntrospector.instance;
+		NopAnnotationIntrospector introspector = NopAnnotationIntrospector.instance;
 
 		Map<Class<?>, JsonDeserializer<?>> deserializerMap = new HashMap<>();
 		JsonDeserializer<Date> deserializer = new DateDeserializers.DateDeserializer();
@@ -445,7 +447,8 @@ public void completeSetup() throws JsonMappingException {
 				.serializers(serializer1)
 				.serializersByType(Collections.singletonMap(Boolean.class, serializer2))
 				.deserializersByType(deserializerMap)
-				.annotationIntrospector(annotationIntrospector)
+				.annotationIntrospector(introspector)
+				.annotationIntrospector(current -> AnnotationIntrospector.pair(current, introspector))
 				.featuresToEnable(SerializationFeature.FAIL_ON_EMPTY_BEANS,
 						DeserializationFeature.UNWRAP_ROOT_VALUE,
 						JsonParser.Feature.ALLOW_BACKSLASH_ESCAPING_ANY_CHARACTER,
@@ -470,8 +473,13 @@ public void completeSetup() throws JsonMappingException {
 		Deserializers deserializers = getDeserializerFactoryConfig(mapper).deserializers().iterator().next();
 		assertThat(deserializers.findBeanDeserializer(SimpleType.construct(Date.class), null, null)).isSameAs(deserializer);
 
-		assertThat(mapper.getSerializationConfig().getAnnotationIntrospector()).isSameAs(annotationIntrospector);
-		assertThat(mapper.getDeserializationConfig().getAnnotationIntrospector()).isSameAs(annotationIntrospector);
+		AnnotationIntrospectorPair pair1 =
+				(AnnotationIntrospectorPair) mapper.getSerializationConfig().getAnnotationIntrospector();
+		AnnotationIntrospectorPair pair2 =
+				(AnnotationIntrospectorPair) mapper.getDeserializationConfig().getAnnotationIntrospector();
+
+		assertThat(pair1.allIntrospectors()).containsExactly(introspector, introspector);
+		assertThat(pair2.allIntrospectors()).containsExactly(introspector, introspector);
 
 		assertThat(mapper.getSerializationConfig().isEnabled(SerializationFeature.FAIL_ON_EMPTY_BEANS)).isTrue();
 		assertThat(mapper.getDeserializationConfig().isEnabled(DeserializationFeature.UNWRAP_ROOT_VALUE)).isTrue();