Add Support for Jackson 3 (#742)

This change adds Jackson 3 support and aligns package naming in the existing Jackson 2 module.

Specific changes:
* Deprecated classes for removal in `io.modelcontextprotocol.json.jackson`/`io.modelcontextprotocol.json.schema.jackson`
* Copied the above to `io.modelcontextprotocol.json.jackson2`/`io.modelcontextprotocol.json.schema.jackson2` in non-deprecated form.
* Added tests for the default McpJsonMapper and JsonSchemaValidator

Author: filiphr

mcp-core/pom.xml

@@ -80,7 +80,7 @@
 		<dependency>
 			<groupId>com.fasterxml.jackson.core</groupId>
 			<artifactId>jackson-annotations</artifactId>
-			<version>${jackson.version}</version>
+			<version>${jackson-annotations.version}</version>
 		</dependency>
 
 		<dependency>
@@ -100,7 +100,7 @@
 		<!-- Test dependencies -->
         <dependency>
             <groupId>io.modelcontextprotocol.sdk</groupId>
-            <artifactId>mcp-json-jackson2</artifactId>
+            <artifactId>mcp-json-jackson3</artifactId>
             <version>0.18.0-SNAPSHOT</version>
             <scope>test</scope>
         </dependency>

mcp-core/src/test/java/io/modelcontextprotocol/spec/McpSchemaTests.java

@@ -10,6 +10,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
+import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
@@ -18,7 +19,7 @@
 
 import org.junit.jupiter.api.Test;
 
-import com.fasterxml.jackson.databind.exc.InvalidTypeIdException;
+import tools.jackson.databind.exc.InvalidTypeIdException;
 
 import io.modelcontextprotocol.spec.McpSchema.TextResourceContents;
 import net.javacrumbs.jsonunit.core.Option;
@@ -58,7 +59,9 @@ void testTextContentDeserialization() throws Exception {
 	void testContentDeserializationWrongType() throws Exception {
 
 		assertThatThrownBy(() -> JSON_MAPPER.readValue("""
-				{"type":"WRONG","text":"XXX"}""", McpSchema.TextContent.class))
+				{"type":"WRONG","text":"XXX"}""", McpSchema.TextContent.class)).isInstanceOf(IOException.class)
+			.hasMessage("Failed to read value")
+			.cause()
 			.isInstanceOf(InvalidTypeIdException.class)
 			.hasMessageContaining(
 					"Could not resolve type id 'WRONG' as a subtype of `io.modelcontextprotocol.spec.McpSchema$TextContent`: known type ids = [audio, image, resource, resource_link, text]");

mcp-json-jackson2/pom.xml

@@ -11,7 +11,7 @@
 	<artifactId>mcp-json-jackson2</artifactId>
 	<packaging>jar</packaging>
 	<name>Java MCP SDK JSON Jackson</name>
-	<description>Java MCP SDK JSON implementation based on Jackson</description>
+	<description>Java MCP SDK JSON implementation based on Jackson 2</description>
 	<url>https://github.com/modelcontextprotocol/java-sdk</url>
 	<scm>
 		<url>https://github.com/modelcontextprotocol/java-sdk</url>
@@ -42,12 +42,12 @@
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
-            <version>${jackson.version}</version>
+            <version>${jackson2.version}</version>
         </dependency>
         <dependency>
             <groupId>com.networknt</groupId>
             <artifactId>json-schema-validator</artifactId>
-            <version>${json-schema-validator.version}</version>
+            <version>${json-schema-validator-jackson2.version}</version>
         </dependency>
 
 		<dependency>

mcp-json-jackson2/src/main/java/io/modelcontextprotocol/json/jackson/JacksonMcpJsonMapper.java

@@ -14,7 +14,12 @@
 /**
  * Jackson-based implementation of JsonMapper. Wraps a Jackson ObjectMapper but keeps the
  * SDK decoupled from Jackson at the API level.
+ *
+ * @deprecated since 18.0.0, use
+ * {@link io.modelcontextprotocol.json.jackson2.JacksonMcpJsonMapper} instead. Will be
+ * removed in 19.0.0
  */
+@Deprecated(forRemoval = true, since = "18.0.0")
 public final class JacksonMcpJsonMapper implements McpJsonMapper {
 
 	private final ObjectMapper objectMapper;

mcp-json-jackson2/src/main/java/io/modelcontextprotocol/json/jackson/JacksonMcpJsonMapperSupplier.java

@@ -13,7 +13,12 @@
  * <p>
  * This implementation provides a {@link McpJsonMapper} backed by a Jackson
  * {@link com.fasterxml.jackson.databind.ObjectMapper}.
+ *
+ * @deprecated since 18.0.0, use
+ * {@link io.modelcontextprotocol.json.jackson2.JacksonMcpJsonMapperSupplier} instead.
+ * Will be removed in 19.0.0.
  */
+@Deprecated(forRemoval = true, since = "18.0.0")
 public class JacksonMcpJsonMapperSupplier implements McpJsonMapperSupplier {
 
 	/**

mcp-json-jackson2/src/main/java/io/modelcontextprotocol/json/jackson2/JacksonMcpJsonMapper.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2026 - 2026 the original author or authors.
+ */
+
+package io.modelcontextprotocol.json.jackson2;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.databind.JavaType;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import io.modelcontextprotocol.json.McpJsonMapper;
+import io.modelcontextprotocol.json.TypeRef;
+
+/**
+ * Jackson-based implementation of JsonMapper. Wraps a Jackson ObjectMapper but keeps the
+ * SDK decoupled from Jackson at the API level.
+ */
+public final class JacksonMcpJsonMapper implements McpJsonMapper {
+
+	private final ObjectMapper objectMapper;
+
+	/**
+	 * Constructs a new JacksonMcpJsonMapper instance with the given ObjectMapper.
+	 * @param objectMapper the ObjectMapper to be used for JSON serialization and
+	 * deserialization. Must not be null.
+	 * @throws IllegalArgumentException if the provided ObjectMapper is null.
+	 */
+	public JacksonMcpJsonMapper(ObjectMapper objectMapper) {
+		if (objectMapper == null) {
+			throw new IllegalArgumentException("ObjectMapper must not be null");
+		}
+		this.objectMapper = objectMapper;
+	}
+
+	/**
+	 * Returns the underlying Jackson {@link ObjectMapper} used for JSON serialization and
+	 * deserialization.
+	 * @return the ObjectMapper instance
+	 */
+	public ObjectMapper getObjectMapper() {
+		return objectMapper;
+	}
+
+	@Override
+	public <T> T readValue(String content, Class<T> type) throws IOException {
+		return objectMapper.readValue(content, type);
+	}
+
+	@Override
+	public <T> T readValue(byte[] content, Class<T> type) throws IOException {
+		return objectMapper.readValue(content, type);
+	}
+
+	@Override
+	public <T> T readValue(String content, TypeRef<T> type) throws IOException {
+		JavaType javaType = objectMapper.getTypeFactory().constructType(type.getType());
+		return objectMapper.readValue(content, javaType);
+	}
+
+	@Override
+	public <T> T readValue(byte[] content, TypeRef<T> type) throws IOException {
+		JavaType javaType = objectMapper.getTypeFactory().constructType(type.getType());
+		return objectMapper.readValue(content, javaType);
+	}
+
+	@Override
+	public <T> T convertValue(Object fromValue, Class<T> type) {
+		return objectMapper.convertValue(fromValue, type);
+	}
+
+	@Override
+	public <T> T convertValue(Object fromValue, TypeRef<T> type) {
+		JavaType javaType = objectMapper.getTypeFactory().constructType(type.getType());
+		return objectMapper.convertValue(fromValue, javaType);
+	}
+
+	@Override
+	public String writeValueAsString(Object value) throws IOException {
+		return objectMapper.writeValueAsString(value);
+	}
+
+	@Override
+	public byte[] writeValueAsBytes(Object value) throws IOException {
+		return objectMapper.writeValueAsBytes(value);
+	}
+
+}

mcp-json-jackson2/src/main/java/io/modelcontextprotocol/json/jackson2/JacksonMcpJsonMapperSupplier.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2026 - 2026 the original author or authors.
+ */
+
+package io.modelcontextprotocol.json.jackson2;
+
+import io.modelcontextprotocol.json.McpJsonMapper;
+import io.modelcontextprotocol.json.McpJsonMapperSupplier;
+
+/**
+ * A supplier of {@link McpJsonMapper} instances that uses the Jackson library for JSON
+ * serialization and deserialization.
+ * <p>
+ * This implementation provides a {@link McpJsonMapper} backed by a Jackson
+ * {@link com.fasterxml.jackson.databind.ObjectMapper}.
+ */
+public class JacksonMcpJsonMapperSupplier implements McpJsonMapperSupplier {
+
+	/**
+	 * Returns a new instance of {@link McpJsonMapper} that uses the Jackson library for
+	 * JSON serialization and deserialization.
+	 * <p>
+	 * The returned {@link McpJsonMapper} is backed by a new instance of
+	 * {@link com.fasterxml.jackson.databind.ObjectMapper}.
+	 * @return a new {@link McpJsonMapper} instance
+	 */
+	@Override
+	public McpJsonMapper get() {
+		return new JacksonMcpJsonMapper(new com.fasterxml.jackson.databind.ObjectMapper());
+	}
+
+}

mcp-json-jackson2/src/main/java/io/modelcontextprotocol/json/schema/jackson/DefaultJsonSchemaValidator.java

@@ -24,7 +24,11 @@
  * NetworkNT JSON Schema Validator library for validation.
  *
  * @author Christian Tzolov
+ * @deprecated since 18.0.0, use
+ * {@link io.modelcontextprotocol.json.schema.jackson2.DefaultJsonSchemaValidator}
+ * instead. Will be removed in 19.0.0.
  */
+@Deprecated(forRemoval = true, since = "18.0.0")
 public class DefaultJsonSchemaValidator implements JsonSchemaValidator {
 
 	private static final Logger logger = LoggerFactory.getLogger(DefaultJsonSchemaValidator.class);

mcp-json-jackson2/src/main/java/io/modelcontextprotocol/json/schema/jackson/JacksonJsonSchemaValidatorSupplier.java

@@ -13,6 +13,9 @@
  *
  * @see JsonSchemaValidatorSupplier
  * @see JsonSchemaValidator
+ * @deprecated since 18.0.0, use
+ * {@link io.modelcontextprotocol.json.schema.jackson2.JacksonJsonSchemaValidatorSupplier}
+ * instead. Will be removed in 19.0.0.
  */
 public class JacksonJsonSchemaValidatorSupplier implements JsonSchemaValidatorSupplier {