Add shortcuts for Jackson mix-in annotations registration

This commit adds support for direct Jackson mix-in annotations registration in
Jackson2ObjectMapperFactoryBean and Jackson2ObjectMapperBuilder.

Issue: SPR-12144

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

@@ -60,6 +60,7 @@ import org.springframework.util.ClassUtils;
  *
  * @author Sebastien Deleuze
  * @author Juergen Hoeller
+ * @author Tadaya Tsuyukubo
  * @since 4.1.1
  * @see #build()
  * @see #configure(ObjectMapper)
@@ -81,6 +82,8 @@ public class Jackson2ObjectMapperBuilder {
 
 	private final Map<Class<?>, JsonDeserializer<?>> deserializers = new LinkedHashMap<Class<?>, JsonDeserializer<?>>();
 
+	private final Map<Class<?>, Class<?>> mixIns = new HashMap<Class<?>, Class<?>>();
+
 	private final Map<Object, Boolean> features = new HashMap<Object, Boolean>();
 
 	private List<Module> modules;
@@ -190,6 +193,21 @@ public class Jackson2ObjectMapperBuilder {
 		return this;
 	}
 
+	/**
+	 * Add mix-in annotations to use for augmenting specified class or interface.
+	 * @param mixIns Map of entries with target classes (or interface) whose annotations
+	 * to effectively override as key and mix-in classes (or interface) whose
+	 * annotations are to be "added" to target's annotations as value.
+	 * @since 4.1.2
+	 * @see com.fasterxml.jackson.databind.ObjectMapper#addMixInAnnotations(Class, Class)
+	 */
+	public Jackson2ObjectMapperBuilder mixIns(Map<Class<?>, Class<?>> mixIns) {
+		if (mixIns != null) {
+			this.mixIns.putAll(mixIns);
+		}
+		return this;
+	}
+
 	/**
 	 * Shortcut for {@link MapperFeature#AUTO_DETECT_FIELDS} option.
 	 */
@@ -414,6 +432,9 @@ public class Jackson2ObjectMapperBuilder {
 		if (this.propertyNamingStrategy != null) {
 			objectMapper.setPropertyNamingStrategy(this.propertyNamingStrategy);
 		}
+		for (Class<?> target : this.mixIns.keySet()) {
+			objectMapper.addMixInAnnotations(target, this.mixIns.get(target));
+		}
 	}
 
 	@SuppressWarnings("unchecked")

spring-web/src/main/java/org/springframework/http/converter/json/Jackson2ObjectMapperFactoryBean.java

@@ -118,6 +118,7 @@ import org.springframework.beans.factory.InitializingBean;
  * @author Rossen Stoyanchev
  * @author Brian Clozel
  * @author Juergen Hoeller
+ * @author Tadaya Tsuyukubo
  * @since 3.2
  */
 public class Jackson2ObjectMapperFactoryBean implements FactoryBean<ObjectMapper>, BeanClassLoaderAware, InitializingBean {
@@ -213,6 +214,18 @@ public class Jackson2ObjectMapperFactoryBean implements FactoryBean<ObjectMapper
 		this.builder.deserializersByType(deserializers);
 	}
 
+	/**
+	 * Add mix-in annotations to use for augmenting specified class or interface.
+	 * @param mixIns Map of entries with target classes (or interface) whose annotations
+	 * to effectively override as key and mix-in classes (or interface) whose
+	 * annotations are to be "added" to target's annotations as value.
+	 * @since 4.1.2
+	 * @see com.fasterxml.jackson.databind.ObjectMapper#addMixInAnnotations(Class, Class)
+	 */
+	public void setMixIns(Map<Class<?>, Class<?>> mixIns) {
+		this.builder.mixIns(mixIns);
+	}
+
 	/**
 	 * Shortcut for {@link MapperFeature#AUTO_DETECT_FIELDS} option.
 	 */

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

@@ -190,6 +190,19 @@ public class Jackson2ObjectMapperBuilderTests {
 		assertSame(strategy, objectMapper.getDeserializationConfig().getPropertyNamingStrategy());
 	}
 
+	@Test
+	public void mixIns() {
+		Class<?> target = String.class;
+		Class<?> mixinSource = Object.class;
+		Map<Class<?>, Class<?>> mixIns = new HashMap<Class<?>, Class<?>>();
+		mixIns.put(target, mixinSource);
+
+		ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json().mixIns(mixIns).build();
+
+		assertEquals(1, objectMapper.mixInCount());
+		assertSame(mixinSource, objectMapper.findMixInClassFor(target));
+	}
+
 	@Test
 	public void completeSetup() {
 		NopAnnotationIntrospector annotationIntrospector = NopAnnotationIntrospector.instance;

spring-web/src/test/java/org/springframework/http/converter/json/Jackson2ObjectMapperFactoryBeanTests.java

@@ -207,6 +207,21 @@ public class Jackson2ObjectMapperFactoryBeanTests {
 		assertSame(strategy, this.factory.getObject().getDeserializationConfig().getPropertyNamingStrategy());
 	}
 
+	@Test
+	public void setMixIns() {
+		Class<?> target = String.class;
+		Class<?> mixinSource = Object.class;
+		Map<Class<?>, Class<?>> mixIns = new HashMap<Class<?>, Class<?>>();
+		mixIns.put(target, mixinSource);
+
+		this.factory.setMixIns(mixIns);
+		this.factory.afterPropertiesSet();
+		ObjectMapper objectMapper = this.factory.getObject();
+
+		assertEquals(1, objectMapper.mixInCount());
+		assertSame(mixinSource, objectMapper.findMixInClassFor(target));
+	}
+
 	@Test
 	public void completeSetup() {
 		NopAnnotationIntrospector annotationIntrospector = NopAnnotationIntrospector.instance;