chore: Add AsyncCloseable interface.

mcp/src/main/java/io/modelcontextprotocol/spec/AsyncCloseable.java

@@ -0,0 +1,24 @@
+package io.modelcontextprotocol.spec;
+
+import reactor.core.publisher.Mono;
+
+/**
+ * Interface for close operations that are asynchronous.
+ */
+public interface AsyncCloseable {
+
+	/**
+	 * Begins the process of closing the resource gracefully, if there is one in progress,
+	 * return the existing one.
+	 * @return A {@link Mono} that completes when the resource has been closed.
+	 */
+	Mono<Void> closeGracefully();
+
+	/**
+	 * Immediately closes the resource gracefully.
+	 */
+	default void close() {
+		this.closeGracefully().subscribe();
+	}
+
+}

mcp/src/main/java/io/modelcontextprotocol/spec/McpServerTransportProvider.java

@@ -29,7 +29,7 @@
  *
  * @author Dariusz Jędrzejczyk
  */
-public interface McpServerTransportProvider {
+public interface McpServerTransportProvider extends AsyncCloseable {
 
 	/**
 	 * Sets the session factory that will be used to create sessions for new clients. An
@@ -52,6 +52,7 @@ public interface McpServerTransportProvider {
 	 * Immediately closes all the transports with connected clients and releases any
 	 * associated resources.
 	 */
+	@Override
 	default void close() {
 		this.closeGracefully().subscribe();
 	}
@@ -61,6 +62,7 @@ default void close() {
 	 * associated resources asynchronously.
 	 * @return a {@link Mono<Void>} that completes when the connections have been closed.
 	 */
+	@Override
 	Mono<Void> closeGracefully();
 
 }

mcp/src/main/java/io/modelcontextprotocol/spec/McpSession.java

@@ -23,7 +23,7 @@
  * @author Christian Tzolov
  * @author Dariusz Jędrzejczyk
  */
-public interface McpSession {
+public interface McpSession extends AsyncCloseable {
 
 	/**
 	 * Sends a request to the model counterparty and expects a response of type T.
@@ -72,11 +72,13 @@ default Mono<Void> sendNotification(String method) {
 	 * Closes the session and releases any associated resources asynchronously.
 	 * @return a {@link Mono<Void>} that completes when the session has been closed.
 	 */
+	@Override
 	Mono<Void> closeGracefully();
 
 	/**
 	 * Closes the session and releases any associated resources.
 	 */
+	@Override
 	void close();
 
 }

mcp/src/main/java/io/modelcontextprotocol/spec/McpTransport.java

@@ -35,7 +35,7 @@
  * @author Christian Tzolov
  * @author Dariusz Jędrzejczyk
  */
-public interface McpTransport {
+public interface McpTransport extends AsyncCloseable {
 
 	/**
 	 * Closes the transport connection and releases any associated resources.
@@ -45,6 +45,7 @@ public interface McpTransport {
 	 * needed. It should handle the graceful shutdown of any active connections.
 	 * </p>
 	 */
+	@Override
 	default void close() {
 		this.closeGracefully().subscribe();
 	}
@@ -54,6 +55,7 @@ default void close() {
 	 * asynchronously.
 	 * @return a {@link Mono<Void>} that completes when the connection has been closed.
 	 */
+	@Override
 	Mono<Void> closeGracefully();
 
 	/**