Moves mcp-json API back into mcp-core for simplified dependencies and support of osgi runtimes

mcp-bom/pom.xml

@@ -40,13 +40,6 @@
                 <version>${project.version}</version>
             </dependency>
 
-            <!-- MCP JSON -->
-            <dependency>
-                <groupId>io.modelcontextprotocol.sdk</groupId>
-                <artifactId>mcp-json</artifactId>
-                <version>${project.version}</version>
-            </dependency>
-
             <!-- MCP JSON Jackson -->
             <dependency>
                 <groupId>io.modelcontextprotocol.sdk</groupId>

mcp-core/pom.xml

@@ -41,6 +41,7 @@
 								Automatic-Module-Name:  ${project.groupId}.${project.artifactId}
 								Import-Package:         jakarta.*;resolution:=optional, \
 								                        *;
+								Service-Component: 		OSGI-INF/io.modelcontextprotocol.json.McpJsonDefaults.xml
 								Export-Package:         io.modelcontextprotocol.*;version="${version}";-noimport:=true
 								-noimportjava:          true;
 								-nouses:                true;
@@ -65,11 +66,6 @@
 	</build>
 
 	<dependencies>
-        <dependency>
-            <groupId>io.modelcontextprotocol.sdk</groupId>
-            <artifactId>mcp-json</artifactId>
-            <version>0.18.0-SNAPSHOT</version>
-        </dependency>
 
 		<dependency>
 			<groupId>org.slf4j</groupId>
@@ -97,21 +93,19 @@
 			<scope>provided</scope>
 		</dependency>
 
-		<!-- Test dependencies -->
-        <dependency>
-            <groupId>io.modelcontextprotocol.sdk</groupId>
-            <artifactId>mcp-json-jackson3</artifactId>
-            <version>0.18.0-SNAPSHOT</version>
-            <scope>test</scope>
-        </dependency>
-
 		<dependency>
 			<groupId>org.springframework</groupId>
 			<artifactId>spring-webmvc</artifactId>
 			<version>${springframework.version}</version>
 			<scope>test</scope>
 		</dependency>
 
+        <dependency>
+            <groupId>tools.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>${jackson3.version}</version>
+            <scope>test</scope>
+        </dependency>
 
 		<dependency>
 			<groupId>io.projectreactor.netty</groupId>

mcp-core/src/main/java/io/modelcontextprotocol/client/McpClient.java

@@ -5,6 +5,7 @@
 package io.modelcontextprotocol.client;
 
 import io.modelcontextprotocol.common.McpTransportContext;
+import io.modelcontextprotocol.json.McpJsonDefaults;
 import io.modelcontextprotocol.json.schema.JsonSchemaValidator;
 import io.modelcontextprotocol.spec.McpClientTransport;
 import io.modelcontextprotocol.spec.McpSchema;
@@ -491,9 +492,12 @@ public McpSyncClient build() {
 
 			McpClientFeatures.Async asyncFeatures = McpClientFeatures.Async.fromSync(syncFeatures);
 
-			return new McpSyncClient(new McpAsyncClient(transport, this.requestTimeout, this.initializationTimeout,
-					jsonSchemaValidator != null ? jsonSchemaValidator : JsonSchemaValidator.getDefault(),
-					asyncFeatures), this.contextProvider);
+			return new McpSyncClient(
+					new McpAsyncClient(transport, this.requestTimeout, this.initializationTimeout,
+							jsonSchemaValidator != null ? jsonSchemaValidator
+									: McpJsonDefaults.getDefaultJsonSchemaValidator(),
+							asyncFeatures),
+					this.contextProvider);
 		}
 
 	}
@@ -826,7 +830,7 @@ public AsyncSpec enableCallToolSchemaCaching(boolean enableCallToolSchemaCaching
 		 */
 		public McpAsyncClient build() {
 			var jsonSchemaValidator = (this.jsonSchemaValidator != null) ? this.jsonSchemaValidator
-					: JsonSchemaValidator.getDefault();
+					: McpJsonDefaults.getDefaultJsonSchemaValidator();
 			return new McpAsyncClient(this.transport, this.requestTimeout, this.initializationTimeout,
 					jsonSchemaValidator,
 					new McpClientFeatures.Async(this.clientInfo, this.capabilities, this.roots,

mcp-core/src/main/java/io/modelcontextprotocol/client/transport/HttpClientSseClientTransport.java

@@ -22,6 +22,7 @@
 import io.modelcontextprotocol.client.transport.customizer.McpAsyncHttpClientRequestCustomizer;
 import io.modelcontextprotocol.client.transport.customizer.McpSyncHttpClientRequestCustomizer;
 import io.modelcontextprotocol.common.McpTransportContext;
+import io.modelcontextprotocol.json.McpJsonDefaults;
 import io.modelcontextprotocol.json.McpJsonMapper;
 import io.modelcontextprotocol.json.TypeRef;
 import io.modelcontextprotocol.spec.HttpHeaders;
@@ -327,7 +328,7 @@ public Builder connectTimeout(Duration connectTimeout) {
 		public HttpClientSseClientTransport build() {
 			HttpClient httpClient = this.clientBuilder.connectTimeout(this.connectTimeout).build();
 			return new HttpClientSseClientTransport(httpClient, requestBuilder, baseUri, sseEndpoint,
-					jsonMapper == null ? McpJsonMapper.getDefault() : jsonMapper, httpRequestCustomizer);
+					jsonMapper == null ? McpJsonDefaults.getDefaultMcpJsonMapper() : jsonMapper, httpRequestCustomizer);
 		}
 
 	}

mcp-core/src/main/java/io/modelcontextprotocol/client/transport/HttpClientStreamableHttpTransport.java

@@ -25,6 +25,7 @@
 import io.modelcontextprotocol.client.transport.customizer.McpAsyncHttpClientRequestCustomizer;
 import io.modelcontextprotocol.client.transport.customizer.McpSyncHttpClientRequestCustomizer;
 import io.modelcontextprotocol.common.McpTransportContext;
+import io.modelcontextprotocol.json.McpJsonDefaults;
 import io.modelcontextprotocol.json.McpJsonMapper;
 import io.modelcontextprotocol.json.TypeRef;
 import io.modelcontextprotocol.spec.ClosedMcpTransportSession;
@@ -822,9 +823,10 @@ public Builder supportedProtocolVersions(List<String> supportedProtocolVersions)
 		 */
 		public HttpClientStreamableHttpTransport build() {
 			HttpClient httpClient = this.clientBuilder.connectTimeout(this.connectTimeout).build();
-			return new HttpClientStreamableHttpTransport(jsonMapper == null ? McpJsonMapper.getDefault() : jsonMapper,
-					httpClient, requestBuilder, baseUri, endpoint, resumableStreams, openConnectionOnStartup,
-					httpRequestCustomizer, supportedProtocolVersions);
+			return new HttpClientStreamableHttpTransport(
+					jsonMapper == null ? McpJsonDefaults.getDefaultMcpJsonMapper() : jsonMapper, httpClient,
+					requestBuilder, baseUri, endpoint, resumableStreams, openConnectionOnStartup, httpRequestCustomizer,
+					supportedProtocolVersions);
 		}
 
 	}

mcp-core/src/main/java/io/modelcontextprotocol/json/McpJsonDefaults.java

@@ -0,0 +1,82 @@
+/**
+ * Copyright 2026 - 2026 the original author or authors.
+ */
+package io.modelcontextprotocol.json;
+
+import io.modelcontextprotocol.json.schema.JsonSchemaValidator;
+import io.modelcontextprotocol.json.schema.JsonSchemaValidatorSupplier;
+import io.modelcontextprotocol.util.McpServiceLoader;
+
+/**
+ * This class is to be used to provide access to the default McpJsonMapper and to the
+ * default JsonSchemaValidator instances via the static methods: getDefaultMcpJsonMapper
+ * and getDefaultJsonSchemaValidator.
+ * <p>
+ * </p>
+ * The initialization of (singleton) instances of this class is different in non-OSGi
+ * environments and OSGi environments. Specifically, in non-OSGi environments The
+ * McpJsonDefaults class will be loaded by whatever classloader is used to call one of the
+ * existing static get methods for the first time. For servers, this will usually be in
+ * response to the creation of the first McpServer instance. At that first time, the
+ * mcpMapperServiceLoader and mcpValidatorServiceLoader will be null, and the
+ * McpJsonDefaults constructor will be called, creating/initializing the
+ * mcpMapperServiceLoader and the mcpValidatorServiceLoader...which will then be used to
+ * call the ServiceLoader.load method.
+ * <p>
+ * </p>
+ * In OSGi environments, upon bundle activation SCR will create a new (singleton) instance
+ * of McpJsonDefaults (via the constructor), and then inject suppliers via the
+ * setMcpJsonMapperSupplier and setJsonSchemaValidatorSupplier methods with the
+ * SCR-discovered instances of those services. This does depend upon the jars/bundles
+ * providing those suppliers to be started/activated. This SCR behavior is dictated by xml
+ * files in OSGi-INF directory of mcp-core (this project/jar/bundle), and the jsonmapper
+ * and jsonschemvalidator provider jars/bundles (e.g. mcp-json-jackson2, 3, or others).
+ *
+ * <p>
+ * </p>
+ *
+ */
+public class McpJsonDefaults {
+
+	protected static McpServiceLoader<McpJsonMapperSupplier, McpJsonMapper> mcpMapperServiceLoader;
+
+	protected static McpServiceLoader<JsonSchemaValidatorSupplier, JsonSchemaValidator> mcpValidatorServiceLoader;
+
+	public McpJsonDefaults() {
+		mcpMapperServiceLoader = new McpServiceLoader<McpJsonMapperSupplier, McpJsonMapper>(
+				McpJsonMapperSupplier.class);
+		mcpValidatorServiceLoader = new McpServiceLoader<JsonSchemaValidatorSupplier, JsonSchemaValidator>(
+				JsonSchemaValidatorSupplier.class);
+	}
+
+	void setMcpJsonMapperSupplier(McpJsonMapperSupplier supplier) {
+		mcpMapperServiceLoader.setSupplier(supplier);
+	}
+
+	void unsetMcpJsonMapperSupplier(McpJsonMapperSupplier supplier) {
+		mcpMapperServiceLoader.unsetSupplier(supplier);
+	}
+
+	public synchronized static McpJsonMapper getDefaultMcpJsonMapper() {
+		if (mcpMapperServiceLoader == null) {
+			new McpJsonDefaults();
+		}
+		return mcpMapperServiceLoader.getDefault();
+	}
+
+	void setJsonSchemaValidatorSupplier(JsonSchemaValidatorSupplier supplier) {
+		mcpValidatorServiceLoader.setSupplier(supplier);
+	}
+
+	void unsetJsonSchemaValidatorSupplier(JsonSchemaValidatorSupplier supplier) {
+		mcpValidatorServiceLoader.unsetSupplier(supplier);
+	}
+
+	public synchronized static JsonSchemaValidator getDefaultJsonSchemaValidator() {
+		if (mcpValidatorServiceLoader == null) {
+			new McpJsonDefaults();
+		}
+		return mcpValidatorServiceLoader.getDefault();
+	}
+
+}

mcp-json/src/main/java/io/modelcontextprotocol/json/McpJsonMapper.java → mcp-core/src/main/java/io/modelcontextprotocol/json/McpJsonMapper.java

@@ -87,24 +87,4 @@ public interface McpJsonMapper {
 	 */
 	byte[] writeValueAsBytes(Object value) throws IOException;
 
-	/**
-	 * Returns the default {@link McpJsonMapper}.
-	 * @return The default {@link McpJsonMapper}
-	 * @throws IllegalStateException If no {@link McpJsonMapper} implementation exists on
-	 * the classpath.
-	 */
-	static McpJsonMapper getDefault() {
-		return McpJsonInternal.getDefaultMapper();
-	}
-
-	/**
-	 * Creates a new default {@link McpJsonMapper}.
-	 * @return The default {@link McpJsonMapper}
-	 * @throws IllegalStateException If no {@link McpJsonMapper} implementation exists on
-	 * the classpath.
-	 */
-	static McpJsonMapper createDefault() {
-		return McpJsonInternal.createDefaultMapper();
-	}
-
 }

mcp-json/src/main/java/io/modelcontextprotocol/json/TypeRef.java → mcp-core/src/main/java/io/modelcontextprotocol/json/TypeRef.java

@@ -9,7 +9,7 @@
 
 /**
  * Captures generic type information at runtime for parameterized JSON (de)serialization.
- * Usage: TypeRef<List<Foo>> ref = new TypeRef<>(){};
+ * Usage: TypeRef<List<Foo>> ref = new TypeRef<>(){};
  */
 public abstract class TypeRef<T> {
 

mcp-json/src/main/java/io/modelcontextprotocol/json/schema/JsonSchemaValidator.java → mcp-core/src/main/java/io/modelcontextprotocol/json/schema/JsonSchemaValidator.java

@@ -41,24 +41,4 @@ public static ValidationResponse asInvalid(String message) {
 	 */
 	ValidationResponse validate(Map<String, Object> schema, Object structuredContent);
 
-	/**
-	 * Creates the default {@link JsonSchemaValidator}.
-	 * @return The default {@link JsonSchemaValidator}
-	 * @throws IllegalStateException If no {@link JsonSchemaValidator} implementation
-	 * exists on the classpath.
-	 */
-	static JsonSchemaValidator createDefault() {
-		return JsonSchemaInternal.createDefaultValidator();
-	}
-
-	/**
-	 * Returns the default {@link JsonSchemaValidator}.
-	 * @return The default {@link JsonSchemaValidator}
-	 * @throws IllegalStateException If no {@link JsonSchemaValidator} implementation
-	 * exists on the classpath.
-	 */
-	static JsonSchemaValidator getDefault() {
-		return JsonSchemaInternal.getDefaultValidator();
-	}
-
 }

mcp-core/src/main/java/io/modelcontextprotocol/server/McpServer.java

@@ -14,6 +14,7 @@
 import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
 
+import io.modelcontextprotocol.json.McpJsonDefaults;
 import io.modelcontextprotocol.json.McpJsonMapper;
 
 import io.modelcontextprotocol.json.schema.JsonSchemaValidator;
@@ -240,10 +241,11 @@ public McpAsyncServer build() {
 					this.instructions);
 
 			var jsonSchemaValidator = (this.jsonSchemaValidator != null) ? this.jsonSchemaValidator
-					: JsonSchemaValidator.getDefault();
+					: McpJsonDefaults.getDefaultJsonSchemaValidator();
 
-			return new McpAsyncServer(transportProvider, jsonMapper == null ? McpJsonMapper.getDefault() : jsonMapper,
-					features, requestTimeout, uriTemplateManagerFactory, jsonSchemaValidator);
+			return new McpAsyncServer(transportProvider,
+					jsonMapper == null ? McpJsonDefaults.getDefaultMcpJsonMapper() : jsonMapper, features,
+					requestTimeout, uriTemplateManagerFactory, jsonSchemaValidator);
 		}
 
 	}
@@ -267,9 +269,10 @@ public McpAsyncServer build() {
 					this.resources, this.resourceTemplates, this.prompts, this.completions, this.rootsChangeHandlers,
 					this.instructions);
 			var jsonSchemaValidator = this.jsonSchemaValidator != null ? this.jsonSchemaValidator
-					: JsonSchemaValidator.getDefault();
-			return new McpAsyncServer(transportProvider, jsonMapper == null ? McpJsonMapper.getDefault() : jsonMapper,
-					features, requestTimeout, uriTemplateManagerFactory, jsonSchemaValidator);
+					: McpJsonDefaults.getDefaultJsonSchemaValidator();
+			return new McpAsyncServer(transportProvider,
+					jsonMapper == null ? McpJsonDefaults.getDefaultMcpJsonMapper() : jsonMapper, features,
+					requestTimeout, uriTemplateManagerFactory, jsonSchemaValidator);
 		}
 
 	}
@@ -834,9 +837,9 @@ public McpSyncServer build() {
 					this.immediateExecution);
 
 			var asyncServer = new McpAsyncServer(transportProvider,
-					jsonMapper == null ? McpJsonMapper.getDefault() : jsonMapper, asyncFeatures, requestTimeout,
-					uriTemplateManagerFactory,
-					jsonSchemaValidator != null ? jsonSchemaValidator : JsonSchemaValidator.getDefault());
+					jsonMapper == null ? McpJsonDefaults.getDefaultMcpJsonMapper() : jsonMapper, asyncFeatures,
+					requestTimeout, uriTemplateManagerFactory, jsonSchemaValidator != null ? jsonSchemaValidator
+							: McpJsonDefaults.getDefaultJsonSchemaValidator());
 			return new McpSyncServer(asyncServer, this.immediateExecution);
 		}
 
@@ -864,10 +867,10 @@ public McpSyncServer build() {
 			McpServerFeatures.Async asyncFeatures = McpServerFeatures.Async.fromSync(syncFeatures,
 					this.immediateExecution);
 			var jsonSchemaValidator = this.jsonSchemaValidator != null ? this.jsonSchemaValidator
-					: JsonSchemaValidator.getDefault();
+					: McpJsonDefaults.getDefaultJsonSchemaValidator();
 			var asyncServer = new McpAsyncServer(transportProvider,
-					jsonMapper == null ? McpJsonMapper.getDefault() : jsonMapper, asyncFeatures, this.requestTimeout,
-					this.uriTemplateManagerFactory, jsonSchemaValidator);
+					jsonMapper == null ? McpJsonDefaults.getDefaultMcpJsonMapper() : jsonMapper, asyncFeatures,
+					this.requestTimeout, this.uriTemplateManagerFactory, jsonSchemaValidator);
 			return new McpSyncServer(asyncServer, this.immediateExecution);
 		}
 
@@ -1871,9 +1874,10 @@ public StatelessAsyncSpecification jsonSchemaValidator(JsonSchemaValidator jsonS
 		public McpStatelessAsyncServer build() {
 			var features = new McpStatelessServerFeatures.Async(this.serverInfo, this.serverCapabilities, this.tools,
 					this.resources, this.resourceTemplates, this.prompts, this.completions, this.instructions);
-			return new McpStatelessAsyncServer(transport, jsonMapper == null ? McpJsonMapper.getDefault() : jsonMapper,
-					features, requestTimeout, uriTemplateManagerFactory,
-					jsonSchemaValidator != null ? jsonSchemaValidator : JsonSchemaValidator.getDefault());
+			return new McpStatelessAsyncServer(transport,
+					jsonMapper == null ? McpJsonDefaults.getDefaultMcpJsonMapper() : jsonMapper, features,
+					requestTimeout, uriTemplateManagerFactory, jsonSchemaValidator != null ? jsonSchemaValidator
+							: McpJsonDefaults.getDefaultJsonSchemaValidator());
 		}
 
 	}
@@ -2351,9 +2355,9 @@ public McpStatelessSyncServer build() {
 					this.resources, this.resourceTemplates, this.prompts, this.completions, this.instructions);
 			var asyncFeatures = McpStatelessServerFeatures.Async.fromSync(syncFeatures, this.immediateExecution);
 			var asyncServer = new McpStatelessAsyncServer(transport,
-					jsonMapper == null ? McpJsonMapper.getDefault() : jsonMapper, asyncFeatures, requestTimeout,
-					uriTemplateManagerFactory,
-					this.jsonSchemaValidator != null ? this.jsonSchemaValidator : JsonSchemaValidator.getDefault());
+					jsonMapper == null ? McpJsonDefaults.getDefaultMcpJsonMapper() : jsonMapper, asyncFeatures,
+					requestTimeout, uriTemplateManagerFactory, this.jsonSchemaValidator != null
+							? this.jsonSchemaValidator : McpJsonDefaults.getDefaultJsonSchemaValidator());
 			return new McpStatelessSyncServer(asyncServer, this.immediateExecution);
 		}
 

mcp-core/src/main/java/io/modelcontextprotocol/server/transport/HttpServletSseServerTransportProvider.java

@@ -15,6 +15,7 @@
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import io.modelcontextprotocol.common.McpTransportContext;
+import io.modelcontextprotocol.json.McpJsonDefaults;
 import io.modelcontextprotocol.json.McpJsonMapper;
 import io.modelcontextprotocol.json.TypeRef;
 import io.modelcontextprotocol.server.McpTransportContextExtractor;
@@ -632,8 +633,8 @@ public HttpServletSseServerTransportProvider build() {
 				throw new IllegalStateException("MessageEndpoint must be set");
 			}
 			return new HttpServletSseServerTransportProvider(
-					jsonMapper == null ? McpJsonMapper.getDefault() : jsonMapper, baseUrl, messageEndpoint, sseEndpoint,
-					keepAliveInterval, contextExtractor);
+					jsonMapper == null ? McpJsonDefaults.getDefaultMcpJsonMapper() : jsonMapper, baseUrl,
+					messageEndpoint, sseEndpoint, keepAliveInterval, contextExtractor);
 		}
 
 	}