GH-1196 Recactor registratio of Kotlin module

Resolves #1196

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/config/ContextFunctionCatalogAutoConfiguration.java

@@ -25,12 +25,14 @@
 import java.util.stream.Collectors;
 
 import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.Module;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 import com.google.gson.Gson;
 import io.cloudevents.spring.messaging.CloudEventMessageConverter;
 
+import org.springframework.beans.BeanUtils;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
@@ -59,6 +61,7 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.FilterType;
 import org.springframework.context.expression.BeanFactoryResolver;
+import org.springframework.core.KotlinDetector;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.convert.converter.GenericConverter;
 import org.springframework.core.convert.support.ConfigurableConversionService;
@@ -215,6 +218,7 @@ private JsonMapper gson(ApplicationContext context) {
 			return new GsonMapper(gson);
 		}
 
+		@SuppressWarnings("unchecked")
 		private JsonMapper jackson(ApplicationContext context) {
 			ObjectMapper mapper;
 			try {
@@ -225,6 +229,19 @@ private JsonMapper jackson(ApplicationContext context) {
 				mapper.registerModule(new JavaTimeModule());
 			}
 
+			if (KotlinDetector.isKotlinPresent()) {
+				try {
+					if (!mapper.getRegisteredModuleIds().contains("com.fasterxml.jackson.module.kotlin.KotlinModule")) {
+						Class<? extends Module> kotlinModuleClass = (Class<? extends Module>)
+								ClassUtils.forName("com.fasterxml.jackson.module.kotlin.KotlinModule", ClassUtils.getDefaultClassLoader());
+						Module kotlinModule = BeanUtils.instantiateClass(kotlinModuleClass);
+						mapper.registerModule(kotlinModule);
+					}
+				}
+				catch (ClassNotFoundException ex) {
+					// jackson-module-kotlin not available
+				}
+			}
 			mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
 			mapper.configure(DeserializationFeature.FAIL_ON_TRAILING_TOKENS, true);
 			mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/config/KotlinLambdaToFunctionAutoConfiguration.java

@@ -22,7 +22,6 @@
 import java.util.function.Function;
 import java.util.function.Supplier;
 
-import com.fasterxml.jackson.module.kotlin.KotlinModule;
 import kotlin.Unit;
 import kotlin.jvm.functions.Function0;
 import kotlin.jvm.functions.Function1;
@@ -37,14 +36,10 @@
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
-import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;
 import org.springframework.cloud.function.context.FunctionRegistration;
 import org.springframework.cloud.function.context.catalog.FunctionTypeUtils;
-import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.ResolvableType;
-import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -62,19 +57,6 @@ public class KotlinLambdaToFunctionAutoConfiguration {
 
 	protected final Log logger = LogFactory.getLog(getClass());
 
-	@Bean
-	@ConditionalOnMissingBean
-	@ConditionalOnClass(name = {"org.springframework.http.converter.json.Jackson2ObjectMapperBuilder",
-			"com.fasterxml.jackson.module.kotlin.KotlinModule"})
-	Jackson2ObjectMapperBuilderCustomizer customizer() {
-		return new Jackson2ObjectMapperBuilderCustomizer() {
-			@Override
-			public void customize(Jackson2ObjectMapperBuilder jacksonObjectMapperBuilder) {
-				jacksonObjectMapperBuilder.modulesToInstall(KotlinModule.class);
-			}
-		};
-	}
-
 
 	@SuppressWarnings({ "unchecked", "rawtypes" })
 	public static final class KotlinFunctionWrapper implements Function<Object, Object>, Supplier<Object>, Consumer<Object>,

spring-cloud-function-context/src/test/java/org/springframework/cloud/function/utils/JsonMapperTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.cloud.function.utils;
 
+import java.lang.reflect.Field;
 import java.nio.charset.StandardCharsets;
 import java.time.ZonedDateTime;
 import java.util.Date;
@@ -38,6 +39,7 @@
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.ResolvableType;
+import org.springframework.util.ReflectionUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -84,6 +86,16 @@ public void testJsonDateTimeConversion() {
 		assertThat(convertedJson).contains("\"zonedDateTime\":\"2024-10-16T16:13:29.964361+02:00\"");
 	}
 
+	@Test
+	public void testKotlinModuleRegistration() throws Exception {
+		ApplicationContext context = SpringApplication.run(EmptyConfiguration.class);
+		JsonMapper jsonMapper = context.getBean(JsonMapper.class);
+		Field mapperField = ReflectionUtils.findField(jsonMapper.getClass(), "mapper");
+		mapperField.setAccessible(true);
+		ObjectMapper mapper = (ObjectMapper) mapperField.get(jsonMapper);
+		assertThat(mapper.getRegisteredModuleIds()).contains("com.fasterxml.jackson.module.kotlin.KotlinModule");
+	}
+
 	@ParameterizedTest
 	@MethodSource("params")
 	public void vanillaArray(JsonMapper mapper) {