Update PING request handler, return empty map instead of empty string

Co-authored-by: NAME <NAME@EXAMPLE.COM>
Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>

Author: 2 people

mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java

@@ -6,6 +6,7 @@
 
 import java.time.Duration;
 import java.util.HashMap;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -403,7 +404,7 @@ private static class AsyncServerImpl extends McpAsyncServer {
 			// Initialize request handlers for standard MCP methods
 
 			// Ping MUST respond with an empty data, but not NULL response.
-			requestHandlers.put(McpSchema.METHOD_PING, (exchange, params) -> Mono.just(""));
+			requestHandlers.put(McpSchema.METHOD_PING, (exchange, params) -> Mono.just(Map.of()));
 
 			// Add tools API handlers if the tool capability is enabled
 			if (this.serverCapabilities.tools() != null) {
@@ -926,7 +927,7 @@ private static final class LegacyAsyncServer extends McpAsyncServer {
 			requestHandlers.put(McpSchema.METHOD_INITIALIZE, asyncInitializeRequestHandler());
 
 			// Ping MUST respond with an empty data, but not NULL response.
-			requestHandlers.put(McpSchema.METHOD_PING, (params) -> Mono.just(""));
+			requestHandlers.put(McpSchema.METHOD_PING, (params) -> Mono.just(Map.of()));
 
 			// Add tools API handlers if the tool capability is enabled
 			if (this.serverCapabilities.tools() != null) {