io.modelcontextprotocol.server.transport

Class WebRxSseServerTransportProvider

java.lang.Object

io.modelcontextprotocol.server.transport.WebRxSseServerTransportProvider

All Implemented Interfaces:

IMcpHttpServerTransport, McpServerTransportProvider, McpServerTransportProviderBase

public class WebRxSseServerTransportProvider
extends Object
implements McpServerTransportProvider, IMcpHttpServerTransport

Server-side implementation of the Model Context Protocol (MCP) transport layer using HTTP with Server-Sent Events (SSE) through Spring WebMVC. This implementation provides a bridge between synchronous WebMVC operations and reactive programming patterns to maintain compatibility with the reactive transport interface.

Key features:

• Implements bidirectional communication using HTTP POST for client-to-server messages and SSE for server-to-client messages
• Manages client sessions with unique IDs for reliable message delivery
• Supports graceful shutdown with proper session cleanup
• Provides JSON-RPC message handling through configured endpoints
• Includes built-in error handling and logging

The transport operates on two main endpoints:

• /sse - The SSE endpoint where clients establish their event stream connection
• A configurable message endpoint where clients send their JSON-RPC messages via HTTP POST

This implementation uses ConcurrentHashMap to safely manage multiple client sessions in a thread-safe manner. Each client session is assigned a unique ID and maintains its own SSE connection.

Author:

Christian Tzolov, Alexandros Pappas, noear

See Also:

McpServerTransportProvider, Handler

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	WebRxSseServerTransportProvider.Builder Builder for creating instances of WebMvcSseServerTransportProvider.

Field Summary

Fields

Modifier and Type	Field and Description
static String	DEFAULT_SSE_ENDPOINT Default SSE endpoint path as specified by the MCP transport specification.
static String	ENDPOINT_EVENT_TYPE Event type for sending the message endpoint URI to clients.
static String	MESSAGE_EVENT_TYPE Event type for JSON-RPC messages sent through the SSE connection.

Constructor Summary

Constructors

Constructor and Description
WebRxSseServerTransportProvider(com.fasterxml.jackson.databind.ObjectMapper objectMapper, String baseUrl, String messageEndpoint, String sseEndpoint, McpTransportContextExtractor<org.noear.solon.core.handle.Context> contextExtractor, Duration keepAliveInterval) Deprecated. Use the builder builder() instead for better configuration options.

Method Summary

Modifier and Type	Method and Description
static WebRxSseServerTransportProvider.Builder	builder() Creates a new Builder instance for configuring and creating instances of WebMvcSseServerTransportProvider.
reactor.core.publisher.Mono<Void>	closeGracefully() Initiates a graceful shutdown of the transport.
String	getMcpEndpoint()
reactor.core.publisher.Mono<Void>	notifyClients(String method, Object params) Broadcasts a notification to all connected clients through their SSE connections.
List<String>	protocolVersions() Returns the protocol version supported by this transport provider.
void	setSessionFactory(McpServerSession.Factory sessionFactory) Sets the session factory that will be used to create sessions for new clients.
void	toHttpHandler(org.noear.solon.SolonApp app)

Methods inherited from class java.lang.Object

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

Methods inherited from interface io.modelcontextprotocol.spec.McpServerTransportProviderBase

close

Field Detail

MESSAGE_EVENT_TYPE

public static final String MESSAGE_EVENT_TYPE

Event type for JSON-RPC messages sent through the SSE connection.

See Also:

Constant Field Values

ENDPOINT_EVENT_TYPE

public static final String ENDPOINT_EVENT_TYPE

Event type for sending the message endpoint URI to clients.

See Also:

Constant Field Values

DEFAULT_SSE_ENDPOINT

public static final String DEFAULT_SSE_ENDPOINT

Default SSE endpoint path as specified by the MCP transport specification.

See Also:

Constant Field Values

Constructor Detail

WebRxSseServerTransportProvider

@Deprecated
public WebRxSseServerTransportProvider(com.fasterxml.jackson.databind.ObjectMapper objectMapper,
                                                   String baseUrl,
                                                   String messageEndpoint,
                                                   String sseEndpoint,
                                                   McpTransportContextExtractor<org.noear.solon.core.handle.Context> contextExtractor,
                                                   Duration keepAliveInterval)

Deprecated. Use the builder builder() instead for better configuration options.

Constructs a new WebMvcSseServerTransportProvider instance.

Parameters:

objectMapper - The ObjectMapper to use for JSON serialization/deserialization of messages.

baseUrl - The base URL for the message endpoint, used to construct the full endpoint URL for clients.

messageEndpoint - The endpoint URI where clients should send their JSON-RPC messages via HTTP POST. This endpoint will be communicated to clients through the SSE connection's initial endpoint event.

sseEndpoint - The endpoint URI where clients establish their SSE connections. * @param keepAliveInterval The interval for sending keep-alive messages to

Throws:

IllegalArgumentException - if any parameter is null

Method Detail

toHttpHandler

public void toHttpHandler(org.noear.solon.SolonApp app)

Specified by:

toHttpHandler in interface IMcpHttpServerTransport

getMcpEndpoint

public String getMcpEndpoint()

Specified by:

getMcpEndpoint in interface IMcpHttpServerTransport

protocolVersions

public List<String> protocolVersions()

Description copied from interface: McpServerTransportProviderBase

Returns the protocol version supported by this transport provider.

Specified by:

protocolVersions in interface McpServerTransportProviderBase

Returns:

the protocol version as a string

setSessionFactory

public void setSessionFactory(McpServerSession.Factory sessionFactory)

Description copied from interface: McpServerTransportProvider

Sets the session factory that will be used to create sessions for new clients. An implementation of the MCP server MUST call this method before any MCP interactions take place.

Specified by:

setSessionFactory in interface McpServerTransportProvider

Parameters:

sessionFactory - the session factory to be used for initiating client sessions

notifyClients

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

Broadcasts a notification to all connected clients through their SSE connections. The message is serialized to JSON and sent as an SSE event with type "message". If any errors occur during sending to a particular client, they are logged but don't prevent sending to other clients.

Specified by:

notifyClients in interface McpServerTransportProviderBase

Parameters:

method - The method name for the notification

params - The parameters for the notification

Returns:

A Mono that completes when the broadcast attempt is finished

See Also:

McpSession#sendNotification(String, Map)

closeGracefully

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

Initiates a graceful shutdown of the transport. This method:

• Sets the closing flag to prevent new connections
• Closes all active SSE connections
• Removes all session records

Specified by:

closeGracefully in interface McpServerTransportProviderBase

Returns:

A Mono that completes when all cleanup operations are finished

builder

public static WebRxSseServerTransportProvider.Builder builder()

Creates a new Builder instance for configuring and creating instances of WebMvcSseServerTransportProvider.

Returns:

A new Builder instance