io.modelcontextprotocol.spec

Class McpClientSession

java.lang.Object

io.modelcontextprotocol.spec.McpClientSession

All Implemented Interfaces:

McpSession

public class McpClientSession
extends Object
implements McpSession

Default implementation of the MCP (Model Context Protocol) session that manages bidirectional JSON-RPC communication between clients and servers. This implementation follows the MCP specification for message exchange and transport handling.

The session manages:

• Request/response handling with unique message IDs
• Notification processing
• Message timeout management
• Transport layer abstraction

Author:

Christian Tzolov, Dariusz Jędrzejczyk

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	McpClientSession.MethodNotFoundError
static interface	McpClientSession.NotificationHandler Functional interface for handling incoming JSON-RPC notifications.
static interface	McpClientSession.RequestHandler<T> Functional interface for handling incoming JSON-RPC requests.

Constructor Summary

Constructors

Constructor and Description
McpClientSession(Duration requestTimeout, McpClientTransport transport, Map<String,McpClientSession.RequestHandler<?>> requestHandlers, Map<String,McpClientSession.NotificationHandler> notificationHandlers) Creates a new McpClientSession with the specified configuration and handlers.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the session immediately, potentially interrupting pending operations.
reactor.core.publisher.Mono<Void>	closeGracefully() Closes the session gracefully, allowing pending operations to complete.
String	getId() Retrieve the session id.
static McpClientSession.MethodNotFoundError	getMethodNotFoundError(String method)
reactor.core.publisher.Mono<Void>	handle(McpSchema.JSONRPCMessage message) Called by the McpServerTransportProvider once the session is determined.
void	openSSE() The client may issue an HTTP GET to the MCP endpoint.
reactor.core.publisher.Mono<Void>	sendNotification(String method) Sends a notification to the model client or server without parameters.
reactor.core.publisher.Mono<Void>	sendNotification(String method, Map<String,Object> params) Sends a JSON-RPC notification.
<T> reactor.core.publisher.Mono<T>	sendRequest(String method, Object requestParams, com.fasterxml.jackson.core.type.TypeReference<T> typeRef) Sends a JSON-RPC request and returns the response.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

McpClientSession

public McpClientSession(Duration requestTimeout,
                        McpClientTransport transport,
                        Map<String,McpClientSession.RequestHandler<?>> requestHandlers,
                        Map<String,McpClientSession.NotificationHandler> notificationHandlers)

Creates a new McpClientSession with the specified configuration and handlers.

Parameters:

requestTimeout - Duration to wait for responses

transport - Transport implementation for message exchange

requestHandlers - Map of method names to request handlers

notificationHandlers - Map of method names to notification handlers

Method Detail

openSSE

public void openSSE()

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.

getMethodNotFoundError

public static McpClientSession.MethodNotFoundError getMethodNotFoundError(String method)

getId

public String getId()

Description copied from interface: McpSession

Retrieve the session id.

Specified by:

getId in interface McpSession

Returns:

session id

handle

public reactor.core.publisher.Mono<Void> handle(McpSchema.JSONRPCMessage message)

Description copied from interface: McpSession

Called by the McpServerTransportProvider once the session is determined. The purpose of this method is to dispatch the message to an appropriate handler as specified by the MCP server implementation (McpAsyncServer or McpSyncServer) via McpServerSession.Factory that the server creates.

Specified by:

handle in interface McpSession

Parameters:

message - the incoming JSON-RPC message

Returns:

a Mono that completes when the message is processed

sendRequest

public <T> reactor.core.publisher.Mono<T> sendRequest(String method,
                                                      Object requestParams,
                                                      com.fasterxml.jackson.core.type.TypeReference<T> typeRef)

Sends a JSON-RPC request and returns the response.

Specified by:

sendRequest in interface McpSession

Type Parameters:

T - The expected response type

Parameters:

method - The method name to call

requestParams - The request parameters

typeRef - Type reference for response deserialization

Returns:

A Mono containing the response

sendNotification

public reactor.core.publisher.Mono<Void> sendNotification(String method)

Description copied from interface: McpSession

Sends a notification to the model client or server without parameters.

This method implements the notification pattern where no response is expected from the counterparty. It's useful for fire-and-forget scenarios.

Specified by:

sendNotification in interface McpSession

Parameters:

method - the name of the notification method to be called on the server

Returns:

a Mono that completes when the notification has been sent

sendNotification

public reactor.core.publisher.Mono<Void> sendNotification(String method,
                                                          Map<String,Object> params)

Sends a JSON-RPC notification.

Specified by:

sendNotification in interface McpSession

Parameters:

method - The method name for the notification

params - The notification parameters

Returns:

A Mono that completes when the notification is sent

closeGracefully

public reactor.core.publisher.Mono<Void> closeGracefully()

Closes the session gracefully, allowing pending operations to complete.

Specified by:

closeGracefully in interface McpSession

Returns:

A Mono that completes when the session is closed

close

public void close()

Closes the session immediately, potentially interrupting pending operations.

Specified by:

close in interface McpSession