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feat: Add transport context extraction support to all MCP servers (#477)

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- Add McpTransportContextExtractor to WebFlux/WebMVC SSE and Streamable transport providers
- Enable extraction of HTTP transport metadata (headers, etc.) for use during request processing
- Pass transport context through reactive context chain using McpTransportContext.KEY
- Add contextExtractor() builder methods for configuring custom extractors
- Update HttpServlet transport providers with same context extraction capability
- Modify McpServerSession to properly propagate transport context to handlers
- Add test coverage with TEST_CONTEXT_EXTRACTOR in integration tests

This allows MCP feature implementations to access HTTP transport level metadata
that was present at request time, enabling use cases like authentication,
request tracing, and custom header processing.

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>

Co-authored-by: Christian Tzolov <christian.tzolov@broadcom.com>
Co-authored-by: Dariusz Jędrzejczyk <dariusz.jedrzejczyk@broadcom.com>
This commit is contained in:
Kevin Stanton 2025-08-10 00:18:05 -05:00 • committed by Christian Tzolov
commit b4fef5241f
1 changed files with 374 additions and 24 deletions
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63
mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java
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@ -23,6 +23,7 @@ import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.BiFunction;
import java.util.function.Function;
@ -36,6 +37,7 @@ import io.modelcontextprotocol.server.McpServer;
import io.modelcontextprotocol.server.McpServerFeatures;
import io.modelcontextprotocol.server.McpSyncServer;
import io.modelcontextprotocol.server.McpSyncServerExchange;
import io.modelcontextprotocol.server.McpTransportContext;
import io.modelcontextprotocol.spec.McpError;
import io.modelcontextprotocol.spec.McpSchema;
import io.modelcontextprotocol.spec.McpSchema.CallToolResult;
@ -55,6 +57,7 @@ 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 io.modelcontextprotocol.util.Utils;
import net.javacrumbs.jsonunit.core.Option;
import reactor.core.publisher.Mono;
import reactor.test.StepVerifier;
@ -750,6 +753,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
var clientBuilder = clientBuilders.get(clientType);
var responseBodyIsNullOrBlank = new AtomicBoolean(false);
var callResponse = new McpSchema.CallToolResult(List.of(new McpSchema.TextContent("CALL RESPONSE")), null);
McpServerFeatures.SyncToolSpecification tool1 = McpServerFeatures.SyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
@ -763,7 +767,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
.GET()
.build(), HttpResponse.BodyHandlers.ofString());
String responseBody = response.body();
assertThat(responseBody).isNotBlank();
responseBodyIsNullOrBlank.set(!Utils.hasText(responseBody));
}
catch (Exception e) {
e.printStackTrace();
@ -786,6 +790,7 @@ public abstract class AbstractMcpClientServerIntegrationTests {
CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("tool1", Map.of()));
assertThat(responseBodyIsNullOrBlank.get()).isFalse();
assertThat(response).isNotNull().isEqualTo(callResponse);
}
@ -829,6 +834,62 @@ public abstract class AbstractMcpClientServerIntegrationTests {
mcpServer.close();
}
@ParameterizedTest(name = "{0} : {displayName} ")
@ValueSource(strings = { "httpclient", "webflux" })
void testToolCallSuccessWithTranportContextExtraction(String clientType) {
var clientBuilder = clientBuilders.get(clientType);
var transportContextIsNull = new AtomicBoolean(false);
var transportContextIsEmpty = new AtomicBoolean(false);
var responseBodyIsNullOrBlank = new AtomicBoolean(false);
var expectedCallResponse = new McpSchema.CallToolResult(
List.of(new McpSchema.TextContent("CALL RESPONSE; ctx=value")), null);
McpServerFeatures.SyncToolSpecification tool1 = McpServerFeatures.SyncToolSpecification.builder()
.tool(Tool.builder().name("tool1").description("tool1 description").inputSchema(emptyJsonSchema).build())
.callHandler((exchange, request) -> {
McpTransportContext transportContext = exchange.transportContext();
transportContextIsNull.set(transportContext == null);
transportContextIsEmpty.set(transportContext.equals(McpTransportContext.EMPTY));
String ctxValue = (String) transportContext.get("important");
try {
String responseBody = "TOOL RESPONSE";
responseBodyIsNullOrBlank.set(!Utils.hasText(responseBody));
}
catch (Exception e) {
e.printStackTrace();
}
return new McpSchema.CallToolResult(
List.of(new McpSchema.TextContent("CALL RESPONSE; ctx=" + ctxValue)), null);
})
.build();
var mcpServer = prepareSyncServerBuilder().capabilities(ServerCapabilities.builder().tools(true).build())
.tools(tool1)
.build();
try (var mcpClient = clientBuilder.build()) {
InitializeResult initResult = mcpClient.initialize();
assertThat(initResult).isNotNull();
assertThat(mcpClient.listTools().tools()).contains(tool1.tool());
CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("tool1", Map.of()));
assertThat(transportContextIsNull.get()).isFalse();
assertThat(transportContextIsEmpty.get()).isFalse();
assertThat(responseBodyIsNullOrBlank.get()).isFalse();
assertThat(response).isNotNull().isEqualTo(expectedCallResponse);
}
mcpServer.close();
}
@ParameterizedTest(name = "{0} : {displayName} ")
@ValueSource(strings = { "httpclient", "webflux" })
void testToolListChangeHandlingSuccess(String clientType) {