io.modelcontextprotocol.server.transport

Class WebRxSseServerTransportProvider

java.lang.Object

io.modelcontextprotocol.server.transport.WebRxSseServerTransportProvider

All Implemented Interfaces:

McpServerTransportProvider

public class WebRxSseServerTransportProvider
extends Object
implements McpServerTransportProvider

Server-side implementation of the MCP (Model Context Protocol) HTTP transport using Server-Sent Events (SSE). This implementation provides a bidirectional communication channel between MCP clients and servers using HTTP POST for client-to-server messages and SSE for server-to-client messages.

Key features:

• Implements the McpServerTransportProvider interface that allows managing McpServerSession instances and enabling their communication with the McpServerTransport abstraction.
• Uses WebFlux for non-blocking request handling and SSE support
• Maintains client sessions for reliable message delivery
• Supports graceful shutdown with session cleanup
• Thread-safe message broadcasting to multiple clients

The transport sets up two main endpoints:

• SSE endpoint (/sse) - For establishing SSE connections with clients
• Message endpoint (configurable) - For receiving JSON-RPC messages from clients

This implementation is thread-safe and can handle multiple concurrent client connections. It uses ConcurrentHashMap for session management and Project Reactor's non-blocking APIs for message processing and delivery. and base JDK8

Author:

Christian Tzolov, Alexandros Pappas, Dariusz Jędrzejczyk, noear

See Also:

McpServerTransport, SseEvent

Nested Class Summary

Nested Classes

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

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 messageEndpoint) Constructs a new WebFlux SSE server transport provider instance with the default SSE endpoint.
WebRxSseServerTransportProvider(com.fasterxml.jackson.databind.ObjectMapper objectMapper, String messageEndpoint, String sseEndpoint) Constructs a new WebFlux SSE server transport provider instance.

Method Summary

Modifier and Type	Method and Description
static WebRxSseServerTransportProvider.Builder	builder()
reactor.core.publisher.Mono<Void>	closeGracefully() Initiates a graceful shutdown of all the sessions.
String	getMessageEndpoint()
String	getSseEndpoint()
void	handleMessage(org.noear.solon.core.handle.Context ctx) Handles incoming JSON-RPC messages from clients.
void	handleSseConnection(org.noear.solon.core.handle.Context ctx) Handles new SSE connection requests from clients.
reactor.core.publisher.Mono<Void>	notifyClients(String method, Map<String,Object> params) Broadcasts a JSON-RPC message to all connected clients through their SSE connections.
void	sendHeartbeat()
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.McpServerTransportProvider

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

public WebRxSseServerTransportProvider(com.fasterxml.jackson.databind.ObjectMapper objectMapper,
                                       String messageEndpoint,
                                       String sseEndpoint)

Constructs a new WebFlux SSE server transport provider instance.

Parameters:

objectMapper - The ObjectMapper to use for JSON serialization/deserialization of MCP messages. Must not be null.

messageEndpoint - The endpoint URI where clients should send their JSON-RPC messages. This endpoint will be communicated to clients during SSE connection setup. Must not be null.

Throws:

IllegalArgumentException - if either parameter is null

WebRxSseServerTransportProvider

public WebRxSseServerTransportProvider(com.fasterxml.jackson.databind.ObjectMapper objectMapper,
                                       String messageEndpoint)

Constructs a new WebFlux SSE server transport provider instance with the default SSE endpoint.

Parameters:

objectMapper - The ObjectMapper to use for JSON serialization/deserialization of MCP messages. Must not be null.

messageEndpoint - The endpoint URI where clients should send their JSON-RPC messages. This endpoint will be communicated to clients during SSE connection setup. Must not be null.

Throws:

IllegalArgumentException - if either parameter is null

Method Detail

sendHeartbeat

public void sendHeartbeat()

toHttpHandler

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

getSseEndpoint

public String getSseEndpoint()

getMessageEndpoint

public String getMessageEndpoint()

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,
                                                       Map<String,Object> params)

Broadcasts a JSON-RPC message to all connected clients through their SSE connections. The message is serialized to JSON and sent as a server-sent event to each active session.

The method:

• Serializes the message to JSON
• Creates a server-sent event with the message data
• Attempts to send the event to all active sessions
• Tracks and reports any delivery failures

Specified by:

notifyClients in interface McpServerTransportProvider

Parameters:

method - The JSON-RPC method to send to clients

params - The method parameters to send to clients

Returns:

A Mono that completes when the message has been sent to all sessions, or errors if any session fails to receive the message

See Also:

McpSession.sendNotification(String, Map)

closeGracefully

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

Initiates a graceful shutdown of all the sessions. This method ensures all active sessions are properly closed and cleaned up.

The shutdown process:

• Marks the transport as closing to prevent new connections
• Closes each active session
• Removes closed sessions from the sessions map
• Times out after 5 seconds if shutdown takes too long

Specified by:

closeGracefully in interface McpServerTransportProvider

Returns:

A Mono that completes when all sessions have been closed

handleSseConnection

public void handleSseConnection(org.noear.solon.core.handle.Context ctx)
                         throws Throwable

Handles new SSE connection requests from clients. Creates a new session for each connection and sets up the SSE event stream.

Parameters:

ctx - The incoming server context

Throws:

Throwable

handleMessage

public void handleMessage(org.noear.solon.core.handle.Context ctx)
                   throws Throwable

Handles incoming JSON-RPC messages from clients. Deserializes the message and processes it through the configured message handler.

The handler:

• Deserializes the incoming JSON-RPC message
• Passes it through the message handler chain
• Returns appropriate HTTP responses based on processing results
• Handles various error conditions with appropriate error responses

Parameters:

ctx - The incoming server request context containing the JSON-RPC message

Throws:

Throwable

builder

public static WebRxSseServerTransportProvider.Builder builder()