Fix the baseUrl is configured with a trailing slash #645

mcp-spring/mcp-spring-webmvc/src/main/java/io/modelcontextprotocol/server/transport/WebMvcSseServerTransportProvider.java

@@ -36,6 +36,7 @@
 import org.springframework.web.servlet.function.ServerRequest;
 import org.springframework.web.servlet.function.ServerResponse;
 import org.springframework.web.servlet.function.ServerResponse.SseBuilder;
+import org.springframework.web.util.UriComponentsBuilder;
 
 /**
  * Server-side implementation of the Model Context Protocol (MCP) transport layer using
@@ -87,6 +88,8 @@ public class WebMvcSseServerTransportProvider implements McpServerTransportProvi
 	 */
 	public static final String ENDPOINT_EVENT_TYPE = "endpoint";
 
+	public static final String SESSION_ID = "sessionId";
+
 	/**
 	 * Default SSE endpoint path as specified by the MCP transport specification.
 	 */
@@ -275,9 +278,7 @@ private ServerResponse handleSseConnection(ServerRequest request) {
 				this.sessions.put(sessionId, session);
 
 				try {
-					sseBuilder.id(sessionId)
-						.event(ENDPOINT_EVENT_TYPE)
-						.data(this.baseUrl + this.messageEndpoint + "?sessionId=" + sessionId);
+					sseBuilder.id(sessionId).event(ENDPOINT_EVENT_TYPE).data(buildEndpointUrl(sessionId));
 				}
 				catch (Exception e) {
 					logger.error("Failed to send initial endpoint event: {}", e.getMessage());
@@ -292,6 +293,14 @@ private ServerResponse handleSseConnection(ServerRequest request) {
 		}
 	}
 
+	private String buildEndpointUrl(String sessionId) {
+		return UriComponentsBuilder.fromUriString(baseUrl)
+			.path(messageEndpoint)
+			.queryParam(SESSION_ID, sessionId)
+			.build()
+			.toUriString();
+	}
+
 	/**
 	 * Handles incoming JSON-RPC messages from clients. This method:
 	 * <ul>
@@ -308,11 +317,11 @@ private ServerResponse handleMessage(ServerRequest request) {
 			return ServerResponse.status(HttpStatus.SERVICE_UNAVAILABLE).body("Server is shutting down");
 		}
 
-		if (request.param("sessionId").isEmpty()) {
+		if (request.param(SESSION_ID).isEmpty()) {
 			return ServerResponse.badRequest().body(new McpError("Session ID missing in message endpoint"));
 		}
 
-		String sessionId = request.param("sessionId").get();
+		String sessionId = request.param(SESSION_ID).get();
 		McpServerSession session = sessions.get(sessionId);
 
 		if (session == null) {

mcp-spring/mcp-spring-webmvc/src/test/java/io/modelcontextprotocol/server/transport/WebMvcSseServerTransportProviderTests.java

@@ -0,0 +1,119 @@
+/*
+ * Copyright 2024 - 2024 the original author or authors.
+ */
+
+package io.modelcontextprotocol.server.transport;
+
+import io.modelcontextprotocol.client.McpClient;
+import io.modelcontextprotocol.client.transport.HttpClientSseClientTransport;
+import io.modelcontextprotocol.common.McpTransportContext;
+import io.modelcontextprotocol.json.McpJsonMapper;
+import io.modelcontextprotocol.server.McpServer;
+import io.modelcontextprotocol.server.TestUtil;
+import io.modelcontextprotocol.server.TomcatTestUtil;
+import io.modelcontextprotocol.spec.McpSchema;
+import org.apache.catalina.LifecycleException;
+import org.apache.catalina.LifecycleState;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.servlet.config.annotation.EnableWebMvc;
+import org.springframework.web.servlet.function.RouterFunction;
+import org.springframework.web.servlet.function.ServerResponse;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for WebMvcSseServerTransportProvider
+ *
+ * @author lance
+ */
+class WebMvcSseServerTransportProviderTests {
+
+	private static final int PORT = TestUtil.findAvailablePort();
+
+	private static final String CUSTOM_CONTEXT_PATH = "/";
+
+	private static final String MESSAGE_ENDPOINT = "/mcp/message";
+
+	private WebMvcSseServerTransportProvider mcpServerTransportProvider;
+
+	McpClient.SyncSpec clientBuilder;
+
+	private TomcatTestUtil.TomcatServer tomcatServer;
+
+	@BeforeEach
+	public void before() {
+		tomcatServer = TomcatTestUtil.createTomcatServer(CUSTOM_CONTEXT_PATH, PORT, TestConfig.class);
+
+		try {
+			tomcatServer.tomcat().start();
+			assertThat(tomcatServer.tomcat().getServer().getState()).isEqualTo(LifecycleState.STARTED);
+		}
+		catch (Exception e) {
+			throw new RuntimeException("Failed to start Tomcat", e);
+		}
+
+		HttpClientSseClientTransport transport = HttpClientSseClientTransport.builder("http://localhost:" + PORT)
+			.sseEndpoint(WebMvcSseServerTransportProvider.DEFAULT_SSE_ENDPOINT)
+			.build();
+
+		clientBuilder = McpClient.sync(transport);
+		mcpServerTransportProvider = tomcatServer.appContext().getBean(WebMvcSseServerTransportProvider.class);
+	}
+
+	@Test
+	void validBaseUrl() {
+		McpServer.async(mcpServerTransportProvider).serverInfo("test-server", "1.0.0").build();
+		try (var client = clientBuilder.clientInfo(new McpSchema.Implementation("Sample " + "client", "0.0.0"))
+			.build()) {
+			assertThat(client.initialize()).isNotNull();
+		}
+	}
+
+	@AfterEach
+	public void after() {
+		if (mcpServerTransportProvider != null) {
+			mcpServerTransportProvider.closeGracefully().block();
+		}
+		if (tomcatServer.appContext() != null) {
+			tomcatServer.appContext().close();
+		}
+		if (tomcatServer.tomcat() != null) {
+			try {
+				tomcatServer.tomcat().stop();
+				tomcatServer.tomcat().destroy();
+			}
+			catch (LifecycleException e) {
+				throw new RuntimeException("Failed to stop Tomcat", e);
+			}
+		}
+	}
+
+	@Configuration
+	@EnableWebMvc
+	static class TestConfig {
+
+		@Bean
+		public WebMvcSseServerTransportProvider webMvcSseServerTransportProvider() {
+
+			return WebMvcSseServerTransportProvider.builder()
+				.baseUrl("http://localhost:" + PORT + "/")
+				.messageEndpoint(MESSAGE_ENDPOINT)
+				.sseEndpoint(WebMvcSseServerTransportProvider.DEFAULT_SSE_ENDPOINT)
+				.jsonMapper(McpJsonMapper.getDefault())
+				.contextExtractor(req -> McpTransportContext.EMPTY)
+				.build();
+		}
+
+		@Bean
+		public RouterFunction<ServerResponse> routerFunction(WebMvcSseServerTransportProvider transportProvider) {
+			return transportProvider.getRouterFunction();
+		}
+
+	}
+
+}