Standard header name used in mcp

Signed-off-by: JermaineHua <crazyhzm@apache.org>

Author: CrazyHZM

mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/client/transport/WebClientStreamableHttpTransport.java

@@ -35,6 +35,8 @@
 import java.util.function.Function;
 import java.util.function.Supplier;
 
+import static io.modelcontextprotocol.spec.McpSchema.Headers.MCP_SESSION_ID;
+
 /**
  * An implementation of the Streamable HTTP protocol as defined by the
  * <code>2025-03-26</code> version of the MCP specification.
@@ -129,7 +131,7 @@ private DefaultMcpTransportSession createTransportSession() {
 			DefaultMcpTransportSession transportSession = this.activeSession.get();
 			return transportSession.sessionId().isEmpty() ? Mono.empty()
 					: webClient.delete().uri(this.endpoint).headers(httpHeaders -> {
-						httpHeaders.add("mcp-session-id", transportSession.sessionId().get());
+						httpHeaders.add(MCP_SESSION_ID, transportSession.sessionId().get());
 					}).retrieve().toBodilessEntity().doOnError(e -> logger.info("Got response {}", e)).then();
 		};
 		return new DefaultMcpTransportSession(onClose);
@@ -185,7 +187,7 @@ private Mono<Disposable> reconnect(McpTransportStream<Disposable> stream) {
 				.uri(this.endpoint)
 				.accept(MediaType.TEXT_EVENT_STREAM)
 				.headers(httpHeaders -> {
-					transportSession.sessionId().ifPresent(id -> httpHeaders.add("mcp-session-id", id));
+					transportSession.sessionId().ifPresent(id -> httpHeaders.add(MCP_SESSION_ID, id));
 					if (stream != null) {
 						stream.lastId().ifPresent(id -> httpHeaders.add("last-event-id", id));
 					}
@@ -243,12 +245,11 @@ public Mono<Void> sendMessage(McpSchema.JSONRPCMessage message) {
 				.uri(this.endpoint)
 				.accept(MediaType.TEXT_EVENT_STREAM, MediaType.APPLICATION_JSON)
 				.headers(httpHeaders -> {
-					transportSession.sessionId().ifPresent(id -> httpHeaders.add("mcp-session-id", id));
+					transportSession.sessionId().ifPresent(id -> httpHeaders.add(MCP_SESSION_ID, id));
 				})
 				.bodyValue(message)
 				.exchangeToFlux(response -> {
-					if (transportSession
-						.markInitialized(response.headers().asHttpHeaders().getFirst("mcp-session-id"))) {
+					if (transportSession.markInitialized(response.headers().asHttpHeaders().getFirst(MCP_SESSION_ID))) {
 						// Once we have a session, we try to open an async stream for
 						// the server to send notifications and requests out-of-band.
 						reconnect(null).contextWrite(sink.contextView()).subscribe();

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

@@ -134,6 +134,18 @@ public static final class ErrorCodes {
 
 	}
 
+	// ---------------------------
+	// JSON-RPC Protocol Headers
+	// ---------------------------
+	/**
+	 * Standard header name used in MCP JSON-RPC request and responses.
+	 */
+	public static final class Headers {
+
+		public static final String MCP_SESSION_ID = "Mcp-Session-Id";
+
+	}
+
 	public sealed interface Request permits InitializeRequest, CallToolRequest, CreateMessageRequest, ElicitRequest,
 			CompleteRequest, GetPromptRequest {