feat(client): adds StreamableHttpClientTransport

mcp/src/main/java/io/modelcontextprotocol/client/McpAsyncClient.java

@@ -160,7 +160,7 @@ public class McpAsyncClient {
 	 * @param features the MCP Client supported features.
 	 */
 	McpAsyncClient(McpClientTransport transport, Duration requestTimeout, Duration initializationTimeout,
-			McpClientFeatures.Async features) {
+			McpClientFeatures.Async features, boolean connectOnInit) {
 
 		Assert.notNull(transport, "Transport must not be null");
 		Assert.notNull(requestTimeout, "Request timeout must not be null");
@@ -235,7 +235,9 @@ public class McpAsyncClient {
 				asyncLoggingNotificationHandler(loggingConsumersFinal));
 
 		this.mcpSession = new McpClientSession(requestTimeout, transport, requestHandlers, notificationHandlers);
-
+		if (connectOnInit) {
+			this.mcpSession.openSSE();
+		}
 	}
 
 	/**
@@ -302,6 +304,18 @@ public Mono<Void> closeGracefully() {
 		return this.mcpSession.closeGracefully();
 	}
 
+	// ---------------------------
+	// open an SSE stream
+	// ---------------------------
+	/**
+	 * The client may issue an HTTP GET to the MCP endpoint. This can be used to open an
+	 * SSE stream, allowing the server to communicate to the client, without the client
+	 * first sending data via HTTP POST.
+	 */
+	public void openSSE() {
+		this.mcpSession.openSSE();
+	}
+
 	// --------------------------
 	// Initialization
 	// --------------------------

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

@@ -157,11 +157,13 @@ class SyncSpec {
 
 		private Duration requestTimeout = Duration.ofSeconds(20); // Default timeout
 
+		private boolean connectOnInit = true; // Default true, for backward compatibility
+
 		private Duration initializationTimeout = Duration.ofSeconds(20);
 
 		private ClientCapabilities capabilities;
 
-		private Implementation clientInfo = new Implementation("Java SDK MCP Client", "1.0.0");
+		private Implementation clientInfo = new Implementation("Java SDK MCP Sync Client", "0.10.0");
 
 		private final Map<String, Root> roots = new HashMap<>();
 
@@ -195,6 +197,17 @@ public SyncSpec requestTimeout(Duration requestTimeout) {
 			return this;
 		}
 
+		/**
+		 * Sets whether to connect to the server during the initialization phase (open an
+		 * SSE stream).
+		 * @param connectOnInit true to open an SSE stream during the initialization
+		 * @return This builder instance for method chaining
+		 */
+		public SyncSpec withConnectOnInit(final boolean connectOnInit) {
+			this.connectOnInit = connectOnInit;
+			return this;
+		}
+
 		/**
 		 * @param initializationTimeout The duration to wait for the initialization
 		 * lifecycle step to complete.
@@ -368,8 +381,8 @@ public McpSyncClient build() {
 
 			McpClientFeatures.Async asyncFeatures = McpClientFeatures.Async.fromSync(syncFeatures);
 
-			return new McpSyncClient(
-					new McpAsyncClient(transport, this.requestTimeout, this.initializationTimeout, asyncFeatures));
+			return new McpSyncClient(new McpAsyncClient(transport, this.requestTimeout, this.initializationTimeout,
+					asyncFeatures, this.connectOnInit));
 		}
 
 	}
@@ -396,11 +409,13 @@ class AsyncSpec {
 
 		private Duration requestTimeout = Duration.ofSeconds(20); // Default timeout
 
+		private boolean connectOnInit = true; // Default true, for backward compatibility
+
 		private Duration initializationTimeout = Duration.ofSeconds(20);
 
 		private ClientCapabilities capabilities;
 
-		private Implementation clientInfo = new Implementation("Spring AI MCP Client", "0.3.1");
+		private Implementation clientInfo = new Implementation("Java SDK MCP Async Client", "0.10.0");
 
 		private final Map<String, Root> roots = new HashMap<>();
 
@@ -434,6 +449,17 @@ public AsyncSpec requestTimeout(Duration requestTimeout) {
 			return this;
 		}
 
+		/**
+		 * Sets whether to connect to the server during the initialization phase (open an
+		 * SSE stream).
+		 * @param connectOnInit true to open an SSE stream during the initialization
+		 * @return This builder instance for method chaining
+		 */
+		public AsyncSpec withConnectOnInit(final boolean connectOnInit) {
+			this.connectOnInit = connectOnInit;
+			return this;
+		}
+
 		/**
 		 * @param initializationTimeout The duration to wait for the initialization
 		 * lifecycle step to complete.
@@ -606,7 +632,8 @@ public McpAsyncClient build() {
 			return new McpAsyncClient(this.transport, this.requestTimeout, this.initializationTimeout,
 					new McpClientFeatures.Async(this.clientInfo, this.capabilities, this.roots,
 							this.toolsChangeConsumers, this.resourcesChangeConsumers, this.promptsChangeConsumers,
-							this.loggingConsumers, this.samplingHandler));
+							this.loggingConsumers, this.samplingHandler),
+					this.connectOnInit);
 		}
 
 	}

mcp/src/main/java/io/modelcontextprotocol/client/McpSyncClient.java

@@ -129,6 +129,18 @@ public boolean closeGracefully() {
 		return true;
 	}
 
+	// ---------------------------
+	// open an SSE stream
+	// ---------------------------
+	/**
+	 * The client may issue an HTTP GET to the MCP endpoint. This can be used to open an
+	 * SSE stream, allowing the server to communicate to the client, without the client
+	 * first sending data via HTTP POST.
+	 */
+	public void openSSE() {
+		this.delegate.openSSE();
+	}
+
 	/**
 	 * The initialization phase MUST be the first interaction between client and server.
 	 * During this phase, the client and server:
@@ -148,9 +160,7 @@ public boolean closeGracefully() {
 	 * The server MUST respond with its own capabilities and information:
 	 * {@link McpSchema.ServerCapabilities}. <br/>
 	 * After successful initialization, the client MUST send an initialized notification
-	 * to indicate it is ready to begin normal operations.
-	 *
-	 * <br/>
+	 * to indicate it is ready to begin normal operations. <br/>
 	 *
 	 * <a href=
 	 * "https://github.com/modelcontextprotocol/specification/blob/main/docs/specification/basic/lifecycle.md#initialization">Initialization
@@ -272,9 +282,8 @@ public McpSchema.ReadResourceResult readResource(McpSchema.ReadResourceRequest r
 
 	/**
 	 * Resource templates allow servers to expose parameterized resources using URI
-	 * templates. Arguments may be auto-completed through the completion API.
-	 *
-	 * Request a list of resource templates the server has.
+	 * templates. Arguments may be auto-completed through the completion API. Request a
+	 * list of resource templates the server has.
 	 * @param cursor the cursor
 	 * @return the list of resource templates result.
 	 */
@@ -293,9 +302,7 @@ public McpSchema.ListResourceTemplatesResult listResourceTemplates() {
 	/**
 	 * Subscriptions. The protocol supports optional subscriptions to resource changes.
 	 * Clients can subscribe to specific resources and receive notifications when they
-	 * change.
-	 *
-	 * Send a resources/subscribe request.
+	 * change. Send a resources/subscribe request.
 	 * @param subscribeRequest the subscribe request contains the uri of the resource to
 	 * subscribe to.
 	 */