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Close response after sending error in McpStreamableServerSession#responseStream (#1041)

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Closes #1040

Signed-off-by: Daniel Garnier-Moiroux <git@garnier.wf>
This commit is contained in:
Daniel Garnier-Moiroux 2026-06-26 16:06:36 +02:00 • committed by GitHub
commit ff78191ebd
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2 changed files with 55 additions and 3 deletions
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10
mcp-core/src/main/java/io/modelcontextprotocol/spec/McpStreamableServerSession.java
View file

@ -214,9 +214,13 @@ public class McpStreamableServerSession implements McpLoggableSession {
// (sink)
if (requestHandler == null) {
MethodNotFoundError error = getMethodNotFoundError(jsonrpcRequest.method());
return transport.sendMessage(
McpSchema.JSONRPCResponse.error(jsonrpcRequest.id(), new McpSchema.JSONRPCResponse.JSONRPCError(
McpSchema.ErrorCodes.METHOD_NOT_FOUND, error.message(), error.data())));
return transport
.sendMessage(
McpSchema.JSONRPCResponse
.error(jsonrpcRequest.id(),
new McpSchema.JSONRPCResponse.JSONRPCError(
McpSchema.ErrorCodes.METHOD_NOT_FOUND, error.message(), error.data())))
.then(transport.closeGracefully());
}
return requestHandler
.handle(new McpAsyncServerExchange(this.id, stream, clientCapabilities.get(), clientInfo.get(),

48
mcp-test/src/test/java/io/modelcontextprotocol/server/HttpServletStreamableIntegrationTests.java
View file

@ -6,6 +6,8 @@ package io.modelcontextprotocol.server;
import java.time.Duration;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Function;
import java.util.stream.Stream;
import io.modelcontextprotocol.AbstractMcpClientServerIntegrationTests;
@ -16,14 +18,19 @@ import io.modelcontextprotocol.server.McpServer.AsyncSpecification;
import io.modelcontextprotocol.server.McpServer.SyncSpecification;
import io.modelcontextprotocol.server.transport.HttpServletStreamableServerTransportProvider;
import io.modelcontextprotocol.server.transport.TomcatTestUtil;
import io.modelcontextprotocol.spec.McpSchema;
import jakarta.servlet.http.HttpServletRequest;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleState;
import org.apache.catalina.startup.Tomcat;
import org.awaitility.Awaitility;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.Timeout;
import org.junit.jupiter.params.provider.Arguments;
import reactor.core.publisher.Mono;
import reactor.test.StepVerifier;
import static org.assertj.core.api.Assertions.assertThat;
@ -96,6 +103,47 @@ class HttpServletStreamableIntegrationTests extends AbstractMcpClientServerInteg
}
}
@Test
void testMissingHandlerReturnsMethodNotFoundError() {
var mcpServer = prepareAsyncServerBuilder().serverInfo("test-server", "1.0.0")
.capabilities(McpSchema.ServerCapabilities.builder().tools(true).build())
.build();
var clientTransport = HttpClientStreamableHttpTransport.builder("http://localhost:" + PORT)
.endpoint(MESSAGE_ENDPOINT)
.build();
try (var mcpClient = McpClient.sync(clientTransport).build()) {
// Create a session using an MCP client
McpSchema.InitializeResult initResult = mcpClient.initialize();
assertThat(initResult).isNotNull();
// Override the response handler in the client to capture responses
AtomicReference<McpSchema.JSONRPCResponse> response = new AtomicReference<>();
var handler = (Function<Mono<McpSchema.JSONRPCMessage>, Mono<McpSchema.JSONRPCMessage>>) (
message) -> message.doOnNext(r -> {
if (r instanceof McpSchema.JSONRPCResponse resp) {
response.set(resp);
}
});
StepVerifier.create(clientTransport.connect(handler)).verifyComplete();
// Send an incorrect request through the transport
StepVerifier
.create(clientTransport.sendMessage(new McpSchema.JSONRPCRequest("foo/bar", "test-request-123")))
.verifyComplete();
// Wait until we've received the response
Awaitility.await().atMost(Duration.ofSeconds(1)).until(() -> response.get() != null);
assertThat(response.get().error().code()).isEqualTo(McpSchema.ErrorCodes.METHOD_NOT_FOUND);
assertThat(response.get().error().message()).isEqualTo("Method not found: foo/bar");
}
finally {
mcpServer.close();
}
}
static McpTransportContextExtractor<HttpServletRequest> TEST_CONTEXT_EXTRACTOR = (r) -> McpTransportContext
.create(Map.of("important", "value"));