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Fix error behavior on unregistered handlers in stateless server handler (#800)

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Instead of throwing an McpError, it now returns with a JSON-RPC method not found error (-32601), aligned with the stateful implementation.

Closes #784
This commit is contained in:
Mathias Geat 2026-07-08 14:42:06 +02:00 • committed by GitHub
commit 5d3decebd6
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1 changed files with 89 additions and 4 deletions
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47
mcp-test/src/test/java/io/modelcontextprotocol/server/HttpServletStatelessIntegrationTests.java
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@ -9,6 +9,7 @@ import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.BiFunction;
import java.util.function.Function;
import io.modelcontextprotocol.client.McpClient;
import io.modelcontextprotocol.client.transport.HttpClientStreamableHttpTransport;
@ -45,6 +46,8 @@ import org.junit.jupiter.api.Timeout;
import org.springframework.mock.web.MockHttpServletRequest;
import org.springframework.mock.web.MockHttpServletResponse;
import org.springframework.web.client.RestClient;
import reactor.core.publisher.Mono;
import reactor.test.StepVerifier;
import static io.modelcontextprotocol.server.transport.HttpServletStatelessServerTransport.APPLICATION_JSON;
import static io.modelcontextprotocol.server.transport.HttpServletStatelessServerTransport.TEXT_EVENT_STREAM;
@ -448,7 +451,7 @@ class HttpServletStatelessIntegrationTests {
"type", "object",
"properties", Map.of(
"name", Map.of("type", "string"),
"age", Map.of("type", "number")),
"age", Map.of("type", "number")),
"required", List.of("name", "age"))); // @formatter:on
Tool calculatorTool = Tool.builder("getMembers")
@ -765,6 +768,48 @@ class HttpServletStatelessIntegrationTests {
mcpServer.close();
}
@Test
void testMissingHandlerReturnsMethodNotFoundError() {
var mcpServer = McpServer.sync(mcpStatelessServerTransport)
.serverInfo("test-server", "1.0.0")
.capabilities(ServerCapabilities.builder().build())
.build();
var clientTransport = HttpClientStreamableHttpTransport.builder("http://localhost:" + PORT)
.endpoint(CUSTOM_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 a request for a non-existent method through the transport, bypassing
// the client's capability checks
StepVerifier
.create(clientTransport.sendMessage(new McpSchema.JSONRPCRequest("foo/bar", "test-request-123")))
.verifyComplete();
// Wait until we've received the response
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.closeGracefully();
}
}
private double evaluateExpression(String expression) {
// Simple expression evaluator for testing
return switch (expression) {