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feat(mcp): Add support for custom context paths in HTTP Servlet SSE server transport

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Enhance HttpServletSseServerTransportProvider to support deployment under non-root context paths by:

- Adding baseUrl field and DEFAULT_BASE_URL constant
- Creating new constructor that accepts a baseUrl parameter
- Extending Builder with baseUrl configuration method
- Prepending baseUrl to message endpoint in SSE events
- Add HttpServletSseServerCustomContextPathTests to verify custom context path functionality
- Extract common Tomcat server setup code to TomcatTestUtil for test reuse

Related to #79

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>
This commit is contained in:
Christian Tzolov 2025-04-06 18:41:25 +02:00
commit 8fc72aed88
4 changed files with 167 additions and 22 deletions
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37
mcp/src/main/java/io/modelcontextprotocol/server/transport/HttpServletSseServerTransportProvider.java
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@ -80,9 +80,14 @@ public class HttpServletSseServerTransportProvider extends HttpServlet implement
/** Event type for endpoint information */
public static final String ENDPOINT_EVENT_TYPE = "endpoint";
public static final String DEFAULT_BASE_URL = "";
/** JSON object mapper for serialization/deserialization */
private final ObjectMapper objectMapper;
/** Base URL for the server transport */
private final String baseUrl;
/** The endpoint path for handling client messages */
private final String messageEndpoint;
@ -108,7 +113,22 @@ public class HttpServletSseServerTransportProvider extends HttpServlet implement
*/
public HttpServletSseServerTransportProvider(ObjectMapper objectMapper, String messageEndpoint,
String sseEndpoint) {
this(objectMapper, DEFAULT_BASE_URL, messageEndpoint, sseEndpoint);
}
/**
* Creates a new HttpServletSseServerTransportProvider instance with a custom SSE
* endpoint.
* @param objectMapper The JSON object mapper to use for message
* serialization/deserialization
* @param baseUrl The base URL for the server transport
* @param messageEndpoint The endpoint path where clients will send their messages
* @param sseEndpoint The endpoint path where clients will establish SSE connections
*/
public HttpServletSseServerTransportProvider(ObjectMapper objectMapper, String baseUrl, String messageEndpoint,
String sseEndpoint) {
this.objectMapper = objectMapper;
this.baseUrl = baseUrl;
this.messageEndpoint = messageEndpoint;
this.sseEndpoint = sseEndpoint;
}
@ -203,7 +223,7 @@ public class HttpServletSseServerTransportProvider extends HttpServlet implement
this.sessions.put(sessionId, session);
// Send initial endpoint event
this.sendEvent(writer, ENDPOINT_EVENT_TYPE, messageEndpoint + "?sessionId=" + sessionId);
this.sendEvent(writer, ENDPOINT_EVENT_TYPE, this.baseUrl + this.messageEndpoint + "?sessionId=" + sessionId);
}
/**
@ -449,6 +469,8 @@ public class HttpServletSseServerTransportProvider extends HttpServlet implement
private ObjectMapper objectMapper = new ObjectMapper();
private String baseUrl = DEFAULT_BASE_URL;
private String messageEndpoint;
private String sseEndpoint = DEFAULT_SSE_ENDPOINT;
@ -464,6 +486,17 @@ public class HttpServletSseServerTransportProvider extends HttpServlet implement
return this;
}
/**
* Sets the base URL for the server transport.
* @param baseUrl The base URL to use
* @return This builder instance for method chaining
*/
public Builder baseUrl(String baseUrl) {
Assert.notNull(baseUrl, "Base URL must not be null");
this.baseUrl = baseUrl;
return this;
}
/**
* Sets the endpoint path where clients will send their messages.
* @param messageEndpoint The message endpoint path
@ -502,7 +535,7 @@ public class HttpServletSseServerTransportProvider extends HttpServlet implement
if (messageEndpoint == null) {
throw new IllegalStateException("MessageEndpoint must be set");
}
return new HttpServletSseServerTransportProvider(objectMapper, messageEndpoint, sseEndpoint);
return new HttpServletSseServerTransportProvider(objectMapper, baseUrl, messageEndpoint, sseEndpoint);
}
}

86
mcp/src/test/java/io/modelcontextprotocol/server/transport/HttpServletSseServerCustomContextPathTests.java Normal file
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@ -0,0 +1,86 @@
/*
* Copyright 2024 - 2024 the original author or authors.
*/
package io.modelcontextprotocol.server.transport;
import com.fasterxml.jackson.databind.ObjectMapper;
import io.modelcontextprotocol.client.McpClient;
import io.modelcontextprotocol.client.transport.HttpClientSseClientTransport;
import io.modelcontextprotocol.server.McpServer;
import io.modelcontextprotocol.spec.McpSchema;
import org.apache.catalina.Context;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleState;
import org.apache.catalina.startup.Tomcat;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import static org.assertj.core.api.Assertions.assertThat;
public class HttpServletSseServerCustomContextPathTests {
private static final int PORT = 8195;
private static final String CUSTOM_CONTEXT_PATH = "/api/v1";
private static final String CUSTOM_SSE_ENDPOINT = "/somePath/sse";
private static final String CUSTOM_MESSAGE_ENDPOINT = "/otherPath/mcp/message";
private HttpServletSseServerTransportProvider mcpServerTransportProvider;
McpClient.SyncSpec clientBuilder;
private Tomcat tomcat;
@BeforeEach
public void before() {
// Create and configure the transport provider
mcpServerTransportProvider = HttpServletSseServerTransportProvider.builder()
.objectMapper(new ObjectMapper())
.baseUrl(CUSTOM_CONTEXT_PATH)
.messageEndpoint(CUSTOM_MESSAGE_ENDPOINT)
.sseEndpoint(CUSTOM_SSE_ENDPOINT)
.build();
tomcat = TomcatTestUtil.createTomcatServer(CUSTOM_CONTEXT_PATH, PORT, mcpServerTransportProvider);
try {
tomcat.start();
assertThat(tomcat.getServer().getState() == LifecycleState.STARTED);
}
catch (Exception e) {
throw new RuntimeException("Failed to start Tomcat", e);
}
this.clientBuilder = McpClient.sync(HttpClientSseClientTransport.builder("http://localhost:" + PORT)
.sseEndpoint(CUSTOM_CONTEXT_PATH + CUSTOM_SSE_ENDPOINT)
.build());
}
@AfterEach
public void after() {
if (mcpServerTransportProvider != null) {
mcpServerTransportProvider.closeGracefully().block();
}
if (tomcat != null) {
try {
tomcat.stop();
tomcat.destroy();
}
catch (LifecycleException e) {
throw new RuntimeException("Failed to stop Tomcat", e);
}
}
}
@Test
void testCustomContextPath() {
McpServer.async(mcpServerTransportProvider).serverInfo("test-server", "1.0.0").build();
var client = clientBuilder.clientInfo(new McpSchema.Implementation("Sample " + "client", "0.0.0")).build();
assertThat(client.initialize()).isNotNull();
}
}

21
mcp/src/test/java/io/modelcontextprotocol/server/transport/HttpServletSseServerTransportProviderIntegrationTests.java
View file

@ -26,7 +26,6 @@ import io.modelcontextprotocol.spec.McpSchema.Role;
import io.modelcontextprotocol.spec.McpSchema.Root;
import io.modelcontextprotocol.spec.McpSchema.ServerCapabilities;
import io.modelcontextprotocol.spec.McpSchema.Tool;
import org.apache.catalina.Context;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleState;
import org.apache.catalina.startup.Tomcat;
@ -59,14 +58,6 @@ public class HttpServletSseServerTransportProviderIntegrationTests {
@BeforeEach
public void before() {
tomcat = new Tomcat();
tomcat.setPort(PORT);
String baseDir = System.getProperty("java.io.tmpdir");
tomcat.setBaseDir(baseDir);
Context context = tomcat.addContext("", baseDir);
// Create and configure the transport provider
mcpServerTransportProvider = HttpServletSseServerTransportProvider.builder()
.objectMapper(new ObjectMapper())
@ -74,18 +65,8 @@ public class HttpServletSseServerTransportProviderIntegrationTests {
.sseEndpoint(CUSTOM_SSE_ENDPOINT)
.build();
// Add transport servlet to Tomcat
org.apache.catalina.Wrapper wrapper = context.createWrapper();
wrapper.setName("mcpServlet");
wrapper.setServlet(mcpServerTransportProvider);
wrapper.setLoadOnStartup(1);
wrapper.setAsyncSupported(true);
context.addChild(wrapper);
context.addServletMappingDecoded("/*", "mcpServlet");
tomcat = TomcatTestUtil.createTomcatServer("", PORT, mcpServerTransportProvider);
try {
var connector = tomcat.getConnector();
connector.setAsyncTimeout(3000);
tomcat.start();
assertThat(tomcat.getServer().getState() == LifecycleState.STARTED);
}

45
mcp/src/test/java/io/modelcontextprotocol/server/transport/TomcatTestUtil.java Normal file
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@ -0,0 +1,45 @@
/*
* Copyright 2025 - 2025 the original author or authors.
*/
package io.modelcontextprotocol.server.transport;
import com.fasterxml.jackson.databind.ObjectMapper;
import jakarta.servlet.Servlet;
import org.apache.catalina.Context;
import org.apache.catalina.LifecycleState;
import org.apache.catalina.startup.Tomcat;
import static org.junit.Assert.assertThat;
/**
* @author Christian Tzolov
*/
public class TomcatTestUtil {
public static Tomcat createTomcatServer(String contextPath, int port, Servlet servlet) {
var tomcat = new Tomcat();
tomcat.setPort(port);
String baseDir = System.getProperty("java.io.tmpdir");
tomcat.setBaseDir(baseDir);
// Context context = tomcat.addContext("", baseDir);
Context context = tomcat.addContext(contextPath, baseDir);
// Add transport servlet to Tomcat
org.apache.catalina.Wrapper wrapper = context.createWrapper();
wrapper.setName("mcpServlet");
wrapper.setServlet(servlet);
wrapper.setLoadOnStartup(1);
wrapper.setAsyncSupported(true);
context.addChild(wrapper);
context.addServletMappingDecoded("/*", "mcpServlet");
var connector = tomcat.getConnector();
connector.setAsyncTimeout(3000);
return tomcat;
}
}