Module io.modelcontextprotocol.sdk.mcp

Package io.modelcontextprotocol.client.transport

Class FlowSseClient

java.lang.Object

io.modelcontextprotocol.client.transport.FlowSseClient

public class FlowSseClient
extends Object

A Server-Sent Events (SSE) client implementation using Java's Flow API for reactive stream processing. This client establishes a connection to an SSE endpoint and processes the incoming event stream, parsing SSE-formatted messages into structured events.

The client supports standard SSE event fields including:

• event - The event type (defaults to "message" if not specified)
• id - The event ID
• data - The event payload data

Events are delivered to a provided FlowSseClient.SseEventHandler which can process events and handle any errors that occur during the connection.

Author:

Christian Tzolov

See Also:

• FlowSseClient.SseEventHandler
• FlowSseClient.SseEvent

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final record	FlowSseClient.SseEvent	Record class representing a Server-Sent Event with its standard fields.
static interface	FlowSseClient.SseEventHandler	Interface for handling SSE events and errors.

Constructor Summary

Constructors

Constructor	Description
FlowSseClient(HttpClient httpClient)	Creates a new FlowSseClient with the specified HTTP client.
FlowSseClient(HttpClient httpClient, HttpRequest.Builder requestBuilder)	Creates a new FlowSseClient with the specified HTTP client and request builder.

Method Summary

Modifier and Type	Method	Description
void	subscribe(String url, FlowSseClient.SseEventHandler eventHandler)	Subscribes to an SSE endpoint and processes the event stream.

Methods inherited from class java.lang.Object

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

Constructor Details

FlowSseClient

public FlowSseClient(HttpClient httpClient)

Creates a new FlowSseClient with the specified HTTP client.

Parameters:

httpClient - the HttpClient instance to use for SSE connections

FlowSseClient

public FlowSseClient(HttpClient httpClient,
 HttpRequest.Builder requestBuilder)

Creates a new FlowSseClient with the specified HTTP client and request builder.

Parameters:

httpClient - the HttpClient instance to use for SSE connections

requestBuilder - the HttpRequest.Builder to use for SSE requests

Method Details

subscribe

public void subscribe(String url,
 FlowSseClient.SseEventHandler eventHandler)

Subscribes to an SSE endpoint and processes the event stream.

This method establishes a connection to the specified URL and begins processing the SSE stream. Events are parsed and delivered to the provided event handler. The connection remains active until either an error occurs or the server closes the connection.

Parameters:

url - the SSE endpoint URL to connect to

eventHandler - the handler that will receive SSE events and error notifications

Throws:

RuntimeException - if the connection fails with a non-200 status code