Refine Jackson ObjectMapper handling

ObjectMapper instantiation is costly, so unless its usage
is one-shot, it is better to create a reusable instance
for upcoming usage.

Also, before this commit, serialization of most Kotlin
classes was not supported due to the lack of proper
Jackson KotlinModule detection.

This commit:
 - Avoids per invocation ObjectMapper instantiation when
   relevant
 - Automatically detects and enables well-known Jackson
   modules including the Kotlin one
 - Removes org.springframework.ai.vectorstore.JsonUtils
   which looks not needed anymore

More optimizations are possible like reusing more
ObjectMapper instances, but this could introduce more breaking
changes so this commit intends to be a good first step.

Kotlin tests will be provided in a follow-up commit.

Additional changes:
 - Update ModelOptionsUtils to use JacksonUtils.instantiateAvailableModules()
 - Add missing license headers
 - Add missing author Javadoc comments

Author: sdeleuze

models/spring-ai-azure-openai/src/main/java/org/springframework/ai/azure/openai/AzureOpenAiImageModel.java

@@ -10,7 +10,7 @@
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationFeature;
-import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import com.fasterxml.jackson.databind.json.JsonMapper;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.ai.azure.openai.metadata.AzureOpenAiImageGenerationMetadata;
@@ -22,6 +22,7 @@
 import org.springframework.ai.image.ImageResponse;
 import org.springframework.ai.image.ImageResponseMetadata;
 import org.springframework.ai.model.ModelOptionsUtils;
+import org.springframework.ai.util.JacksonUtils;
 import org.springframework.util.Assert;
 
 import java.util.List;
@@ -33,6 +34,7 @@
  * {@link OpenAIClient}.
  *
  * @author Benoit Moussaud
+ * @author Sebastien Deleuze
  * @see ImageModel
  * @see com.azure.ai.openai.OpenAIClient
  * @since 1.0.0
@@ -47,6 +49,8 @@ public class AzureOpenAiImageModel implements ImageModel {
 
 	private final AzureOpenAiImageOptions defaultOptions;
 
+	private final ObjectMapper objectMapper;
+
 	public AzureOpenAiImageModel(OpenAIClient openAIClient) {
 		this(openAIClient, AzureOpenAiImageOptions.builder().withDeploymentName(DEFAULT_DEPLOYMENT_NAME).build());
 	}
@@ -56,6 +60,11 @@ public AzureOpenAiImageModel(OpenAIClient microsoftOpenAiClient, AzureOpenAiImag
 		Assert.notNull(options, "AzureOpenAiChatOptions must not be null");
 		this.openAIClient = microsoftOpenAiClient;
 		this.defaultOptions = options;
+		this.objectMapper = JsonMapper.builder()
+			.addModules(JacksonUtils.instantiateAvailableModules())
+			.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
+			.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
+			.build();
 	}
 
 	public AzureOpenAiImageOptions getDefaultOptions() {
@@ -88,11 +97,8 @@ public ImageResponse call(ImagePrompt imagePrompt) {
 	}
 
 	private String toPrettyJson(Object object) {
-		ObjectMapper objectMapper = new ObjectMapper().disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
-			.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
-			.registerModule(new JavaTimeModule());
 		try {
-			return objectMapper.writeValueAsString(object);
+			return this.objectMapper.writeValueAsString(object);
 		}
 		catch (JsonProcessingException e) {
 			return "JsonProcessingException:" + e + " [" + object.toString() + "]";

models/spring-ai-vertex-ai-palm2/src/main/java/org/springframework/ai/vertexai/palm2/api/VertexAiPaLm2Api.java

@@ -25,7 +25,9 @@
 import com.fasterxml.jackson.annotation.JsonInclude.Include;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.json.JsonMapper;
 
+import org.springframework.ai.util.JacksonUtils;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.client.ClientHttpResponse;
@@ -116,6 +118,8 @@ public class VertexAiPaLm2Api {
 
 	private final String embeddingModel;
 
+	private final ObjectMapper objectMapper;
+
 	/**
 	 * Create a new chat completion api.
 	 * @param apiKey vertex apiKey.
@@ -138,6 +142,7 @@ public VertexAiPaLm2Api(String baseUrl, String apiKey, String model, String embe
 		this.chatModel = model;
 		this.embeddingModel = embeddingModel;
 		this.apiKey = apiKey;
+		this.objectMapper = JsonMapper.builder().addModules(JacksonUtils.instantiateAvailableModules()).build();
 
 		Consumer<HttpHeaders> jsonContentHeaders = headers -> {
 			headers.setAccept(List.of(MediaType.APPLICATION_JSON));
@@ -154,7 +159,7 @@ public boolean hasError(ClientHttpResponse response) throws IOException {
 			public void handleError(ClientHttpResponse response) throws IOException {
 				if (response.getStatusCode().isError()) {
 					throw new RuntimeException(String.format("%s - %s", response.getStatusCode().value(),
-							new ObjectMapper().readValue(response.getBody(), ResponseError.class)));
+							objectMapper.readValue(response.getBody(), ResponseError.class)));
 				}
 			}
 		};

spring-ai-core/src/main/java/org/springframework/ai/converter/BeanOutputConverter.java

@@ -21,8 +21,11 @@
 import java.lang.reflect.Type;
 import java.util.Objects;
 
+import com.fasterxml.jackson.databind.json.JsonMapper;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+
+import org.springframework.ai.util.JacksonUtils;
 import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.lang.NonNull;
 
@@ -34,7 +37,6 @@
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.ObjectWriter;
-import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 import com.github.victools.jsonschema.generator.Option;
 import com.github.victools.jsonschema.generator.SchemaGenerator;
 import com.github.victools.jsonschema.generator.SchemaGeneratorConfig;
@@ -54,6 +56,7 @@
  * @author Sebastian Ullrich
  * @author Kirk Lund
  * @author Josh Long
+ * @author Sebastien Deleuze
  */
 public class BeanOutputConverter<T> implements StructuredOutputConverter<T> {
 
@@ -65,12 +68,10 @@ public class BeanOutputConverter<T> implements StructuredOutputConverter<T> {
 	/**
 	 * The target class type reference to which the output will be converted.
 	 */
-	@SuppressWarnings({ "FieldMayBeFinal" })
-	private TypeReference<T> typeRef;
+	private final TypeReference<T> typeRef;
 
 	/** The object mapper used for deserialization and other JSON operations. */
-	@SuppressWarnings("FieldMayBeFinal")
-	private ObjectMapper objectMapper;
+	private final ObjectMapper objectMapper;
 
 	/**
 	 * Constructor to initialize with the target type's class.
@@ -149,7 +150,7 @@ private void generateSchema() {
 		SchemaGeneratorConfig config = configBuilder.build();
 		SchemaGenerator generator = new SchemaGenerator(config);
 		JsonNode jsonNode = generator.generateSchema(this.typeRef.getType());
-		ObjectWriter objectWriter = new ObjectMapper().writer(new DefaultPrettyPrinter()
+		ObjectWriter objectWriter = this.objectMapper.writer(new DefaultPrettyPrinter()
 			.withObjectIndenter(new DefaultIndenter().withLinefeed(System.lineSeparator())));
 		try {
 			this.jsonSchema = objectWriter.writeValueAsString(jsonNode);
@@ -201,10 +202,10 @@ public T convert(@NonNull String text) {
 	 * @return Configured object mapper.
 	 */
 	protected ObjectMapper getObjectMapper() {
-		ObjectMapper mapper = new ObjectMapper();
-		mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
-		mapper.registerModule(new JavaTimeModule());
-		return mapper;
+		return JsonMapper.builder()
+			.addModules(JacksonUtils.instantiateAvailableModules())
+			.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
+			.build();
 	}
 
 	/**

spring-ai-core/src/main/java/org/springframework/ai/model/ModelOptionsUtils.java

@@ -26,16 +26,23 @@
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.stream.Collectors;
 
+import org.springframework.ai.util.JacksonUtils;
+import org.springframework.beans.BeanWrapper;
+import org.springframework.beans.BeanWrapperImpl;
+import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+import org.springframework.util.ObjectUtils;
+
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.json.JsonMapper;
 import com.fasterxml.jackson.databind.node.ArrayNode;
 import com.fasterxml.jackson.databind.node.ObjectNode;
-import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 import com.github.victools.jsonschema.generator.Option;
 import com.github.victools.jsonschema.generator.OptionPreset;
 import com.github.victools.jsonschema.generator.SchemaGenerator;
@@ -46,12 +53,6 @@
 import com.github.victools.jsonschema.module.jackson.JacksonOption;
 import com.github.victools.jsonschema.module.swagger2.Swagger2Module;
 
-import org.springframework.beans.BeanWrapper;
-import org.springframework.beans.BeanWrapperImpl;
-import org.springframework.util.Assert;
-import org.springframework.util.CollectionUtils;
-import org.springframework.util.ObjectUtils;
-
 /**
  * Utility class for manipulating {@link ModelOptions} objects.
  *
@@ -61,10 +62,11 @@
  */
 public abstract class ModelOptionsUtils {
 
-	public static final ObjectMapper OBJECT_MAPPER = new ObjectMapper()
+	public static final ObjectMapper OBJECT_MAPPER = JsonMapper.builder()
 		.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
 		.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
-		.registerModule(new JavaTimeModule());
+		.addModules(JacksonUtils.instantiateAvailableModules())
+		.build();
 
 	private static final List<String> BEAN_MERGE_FIELD_EXCISIONS = List.of("class");
 

spring-ai-core/src/main/java/org/springframework/ai/model/function/FunctionCallbackWrapper.java

@@ -21,18 +21,22 @@
 import org.springframework.ai.chat.model.ToolContext;
 import org.springframework.ai.model.ModelOptionsUtils;
 import org.springframework.ai.model.function.FunctionCallbackContext.SchemaType;
+import org.springframework.ai.util.JacksonUtils;
 import org.springframework.util.Assert;
 
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.SerializationFeature;
-import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import com.fasterxml.jackson.databind.json.JsonMapper;
 
 /**
  * Note that the underlying function is responsible for converting the output into format
  * that can be consumed by the Model. The default implementation converts the output into
  * String before sending it to the Model. Provide a custom function responseConverter
  * implementation to override this.
+ * 
+ * @author Christian Tzolov
+ * @author Sebastien Deleuze
  *
  */
 public class FunctionCallbackWrapper<I, O> extends AbstractFunctionCallback<I, O> {
@@ -90,10 +94,7 @@ public Builder(Function<I, O> function) {
 
 		private String inputTypeSchema;
 
-		private ObjectMapper objectMapper = new ObjectMapper()
-			.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
-			.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
-			.registerModule(new JavaTimeModule());
+		private ObjectMapper objectMapper;
 
 		public Builder<I, O> withName(String name) {
 			Assert.hasText(name, "Name must not be empty");
@@ -142,7 +143,14 @@ public FunctionCallbackWrapper<I, O> build() {
 			Assert.hasText(this.name, "Name must not be empty");
 			Assert.hasText(this.description, "Description must not be empty");
 			Assert.notNull(this.responseConverter, "ResponseConverter must not be null");
-			Assert.notNull(this.objectMapper, "ObjectMapper must not be null");
+
+			if (this.objectMapper == null) {
+				this.objectMapper = JsonMapper.builder()
+					.addModules(JacksonUtils.instantiateAvailableModules())
+					.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
+					.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
+					.build();
+			}
 
 			if (this.inputType == null) {
 				if (this.function != null) {

spring-ai-core/src/main/java/org/springframework/ai/parser/BeanOutputParser.java

@@ -22,6 +22,7 @@
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.ObjectWriter;
+import com.fasterxml.jackson.databind.json.JsonMapper;
 import com.github.victools.jsonschema.generator.SchemaGenerator;
 import com.github.victools.jsonschema.generator.SchemaGeneratorConfig;
 import com.github.victools.jsonschema.generator.SchemaGeneratorConfigBuilder;
@@ -30,6 +31,8 @@
 import java.util.Map;
 import java.util.Objects;
 
+import org.springframework.ai.util.JacksonUtils;
+
 import static com.github.victools.jsonschema.generator.OptionPreset.PLAIN_JSON;
 import static com.github.victools.jsonschema.generator.SchemaVersion.DRAFT_2020_12;
 
@@ -91,7 +94,7 @@ private void generateSchema() {
 		SchemaGeneratorConfig config = configBuilder.build();
 		SchemaGenerator generator = new SchemaGenerator(config);
 		JsonNode jsonNode = generator.generateSchema(this.clazz);
-		ObjectWriter objectWriter = new ObjectMapper().writer(new DefaultPrettyPrinter()
+		ObjectWriter objectWriter = this.objectMapper.writer(new DefaultPrettyPrinter()
 			.withObjectIndenter(new DefaultIndenter().withLinefeed(System.lineSeparator())));
 		try {
 			this.jsonSchema = objectWriter.writeValueAsString(jsonNode);
@@ -142,9 +145,10 @@ private String jsonSchemaToInstance(String text) {
 	 * @return Configured object mapper.
 	 */
 	protected ObjectMapper getObjectMapper() {
-		ObjectMapper mapper = new ObjectMapper();
-		mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
-		return mapper;
+		return JsonMapper.builder()
+			.addModules(JacksonUtils.instantiateAvailableModules())
+			.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
+			.build();
 	}
 
 	/**

spring-ai-core/src/main/java/org/springframework/ai/util/JacksonUtils.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2024 - 2024 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.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.ai.util;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.fasterxml.jackson.databind.Module;
+
+import org.springframework.beans.BeanUtils;
+import org.springframework.core.KotlinDetector;
+import org.springframework.util.ClassUtils;
+
+/**
+ * Utility methods for Jackson.
+ *
+ * @author Sebastien Deleuze
+ */
+public abstract class JacksonUtils {
+
+	/**
+	 * Instantiate well-known Jackson modules available in the classpath.
+	 * <p>
+	 * Supports the follow-modules: <code>Jdk8Module</code>, <code>JavaTimeModule</code>,
+	 * <code>ParameterNamesModule</code> and <code>KotlinModule</code>.
+	 * @return The list of instantiated modules.
+	 */
+	@SuppressWarnings("unchecked")
+	public static List<Module> instantiateAvailableModules() {
+		List<Module> modules = new ArrayList<>();
+		try {
+			Class<? extends com.fasterxml.jackson.databind.Module> jdk8ModuleClass = (Class<? extends Module>) ClassUtils
+				.forName("com.fasterxml.jackson.datatype.jdk8.Jdk8Module", null);
+			com.fasterxml.jackson.databind.Module jdk8Module = BeanUtils.instantiateClass(jdk8ModuleClass);
+			modules.add(jdk8Module);
+		}
+		catch (ClassNotFoundException ex) {
+			// jackson-datatype-jdk8 not available
+		}
+
+		try {
+			Class<? extends com.fasterxml.jackson.databind.Module> javaTimeModuleClass = (Class<? extends Module>) ClassUtils
+				.forName("com.fasterxml.jackson.datatype.jsr310.JavaTimeModule", null);
+			com.fasterxml.jackson.databind.Module javaTimeModule = BeanUtils.instantiateClass(javaTimeModuleClass);
+			modules.add(javaTimeModule);
+		}
+		catch (ClassNotFoundException ex) {
+			// jackson-datatype-jsr310 not available
+		}
+
+		try {
+			Class<? extends com.fasterxml.jackson.databind.Module> parameterNamesModuleClass = (Class<? extends Module>) ClassUtils
+				.forName("com.fasterxml.jackson.module.paramnames.ParameterNamesModule", null);
+			com.fasterxml.jackson.databind.Module parameterNamesModule = BeanUtils
+				.instantiateClass(parameterNamesModuleClass);
+			modules.add(parameterNamesModule);
+		}
+		catch (ClassNotFoundException ex) {
+			// jackson-module-parameter-names not available
+		}
+
+		// Kotlin present?
+		if (KotlinDetector.isKotlinPresent()) {
+			try {
+				Class<? extends com.fasterxml.jackson.databind.Module> kotlinModuleClass = (Class<? extends Module>) ClassUtils
+					.forName("com.fasterxml.jackson.module.kotlin.KotlinModule", null);
+				Module kotlinModule = BeanUtils.instantiateClass(kotlinModuleClass);
+				modules.add(kotlinModule);
+			}
+			catch (ClassNotFoundException ex) {
+				// jackson-module-kotlin not available
+			}
+		}
+		return modules;
+	}
+
+}