Depend on SNAPSHOT version of Helidon. Initial switch to SSE connection to support MCP features.

Author: spericas

examples/calendar/pom.xml

@@ -23,7 +23,7 @@
     <parent>
         <groupId>io.helidon.applications</groupId>
         <artifactId>helidon-se</artifactId>
-        <version>4.3.0-M1</version>
+        <version>4.3.0-SNAPSHOT</version>
         <relativePath/>
     </parent>
 

examples/calendar/src/test/java/io/helidon/extensions/mcp/examples/calendar/StreamableHttpClientTest.java

@@ -16,6 +16,8 @@
 
 package io.helidon.extensions.mcp.examples.calendar;
 
+import java.time.Duration;
+
 import io.helidon.webserver.WebServer;
 import io.helidon.webserver.testing.junit5.ServerTest;
 
@@ -30,7 +32,9 @@ class StreamableHttpClientTest extends BaseTest {
     StreamableHttpClientTest(WebServer server) {
         this.client = McpClient.sync(HttpClientStreamableHttpTransport.builder("http://localhost:" + server.port())
                                              .endpoint("/calendar")
-                                             .build()).build();
+                                             .build())
+                .requestTimeout(Duration.ofSeconds(100000))
+                .build();
         client.initialize();
     }
 

examples/weather-application/mcp-client/pom.xml

@@ -23,7 +23,7 @@
     <parent>
         <groupId>io.helidon.applications</groupId>
         <artifactId>helidon-se</artifactId>
-        <version>4.3.0-M1</version>
+        <version>4.3.0-SNAPSHOT</version>
         <relativePath/>
     </parent>
 

examples/weather-application/mcp-server-declarative/pom.xml

@@ -23,7 +23,7 @@
     <parent>
         <groupId>io.helidon.applications</groupId>
         <artifactId>helidon-se</artifactId>
-        <version>4.3.0-M1</version>
+        <version>4.3.0-SNAPSHOT</version>
         <relativePath/>
     </parent>
 

examples/weather-application/mcp-server/pom.xml

@@ -23,7 +23,7 @@
     <parent>
         <groupId>io.helidon.applications</groupId>
         <artifactId>helidon-se</artifactId>
-        <version>4.3.0-M1</version>
+        <version>4.3.0-SNAPSHOT</version>
         <relativePath/>
     </parent>
 

pom.xml

@@ -60,7 +60,7 @@
 
     <properties>
         <version.java>21</version.java>
-        <helidon.version>4.3.0-M1</helidon.version>
+        <helidon.version>4.3.0-SNAPSHOT</helidon.version>
 
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

server/src/main/java/io/helidon/extensions/mcp/server/McpFeatures.java

@@ -16,16 +16,33 @@
 
 package io.helidon.extensions.mcp.server;
 
+import java.util.Objects;
+import java.util.Optional;
+
+import io.helidon.webserver.jsonrpc.JsonRpcResponse;
+import io.helidon.webserver.sse.SseSink;
+
 /**
  * Support for optional client features like {@link McpProgress} and {@link McpLogger}.
  */
 public final class McpFeatures {
-    private final McpProgress progress;
-    private final McpLogger logger;
+    private final JsonRpcResponse response;
+    private final McpSession session;
+
+    private McpProgress progress;
+    private McpLogger logger;
+    private SseSink sseSink;
 
     McpFeatures(McpSession session) {
-        this.logger = new McpLogger(session);
-        this.progress = new McpProgress(session);
+        Objects.requireNonNull(session, "session is null");
+        this.session = session;
+        this.response = null;
+    }
+
+    McpFeatures(JsonRpcResponse response) {
+        Objects.requireNonNull(response, "response is null");
+        this.response = response;
+        this.session = null;
     }
 
     /**
@@ -34,6 +51,14 @@ public final class McpFeatures {
      * @return progress
      */
     public McpProgress progress() {
+        if (progress == null) {
+            if (response != null) {
+                sseSink = getOrCreateSseSink();
+                progress = new McpProgress(sseSink);
+            } else if (session != null) {
+                progress = new McpProgress(session);
+            }
+        }
         return progress;
     }
 
@@ -43,6 +68,33 @@ public McpProgress progress() {
      * @return logging
      */
     public McpLogger logger() {
+        if (logger == null) {
+            if (response != null) {
+                sseSink = getOrCreateSseSink();
+                logger = new McpLogger(sseSink);
+            } else if (session != null) {
+                logger = new McpLogger(session);
+            }
+        }
         return logger;
     }
+
+    /**
+     * Get access to underlying SSE sink, if available. This method is package private.
+     *
+     * @return optional SSE sink
+     */
+    Optional<SseSink> sseSink() {
+        return Optional.ofNullable(sseSink);
+    }
+
+    /**
+     * Get or create an SSE sink.
+     *
+     * @return the SSE sink
+     */
+    private SseSink getOrCreateSseSink() {
+        Objects.requireNonNull(response, "response is null");
+        return sseSink != null ? sseSink : response.sink(SseSink.TYPE);
+    }
 }

server/src/main/java/io/helidon/extensions/mcp/server/McpLogger.java

@@ -18,16 +18,30 @@
 
 import java.util.Objects;
 
+import io.helidon.http.sse.SseEvent;
+import io.helidon.webserver.sse.SseSink;
+
 /**
  * Mcp logger to send notification to the client.
  */
 public final class McpLogger {
     private final String name;
     private final McpSession session;
+    private final SseSink sseSink;
     private Level level;
 
     McpLogger(McpSession session) {
+        Objects.requireNonNull(session, "session is null");
         this.session = session;
+        this.sseSink = null;
+        this.level = Level.INFO;
+        this.name = "helidon-logger";
+    }
+
+    McpLogger(SseSink sseSink) {
+        Objects.requireNonNull(sseSink, "sseSink is null");
+        this.session = null;
+        this.sseSink = sseSink;
         this.level = Level.INFO;
         this.name = "helidon-logger";
     }
@@ -42,7 +56,14 @@ public void log(Level level, String message) {
         Objects.requireNonNull(level, "level must not be null");
         Objects.requireNonNull(message, "message must not be null");
         if (level.ordinal() >= this.level.ordinal()) {
-            session.send(McpJsonRpc.createLoggingNotification(level, name, message));
+            if (sseSink != null) {
+                sseSink.emit(SseEvent.builder()
+                                     .name("message")
+                                     .data(McpJsonRpc.createLoggingNotification(level, name, message))
+                                     .build());
+            } else if (session != null) {
+                session.send(McpJsonRpc.createLoggingNotification(level, name, message));
+            }
         }
     }
 

server/src/main/java/io/helidon/extensions/mcp/server/McpProgress.java

@@ -16,18 +16,34 @@
 
 package io.helidon.extensions.mcp.server;
 
+import java.util.Objects;
+
+import io.helidon.http.sse.SseEvent;
+import io.helidon.webserver.sse.SseSink;
+
 /**
  * Progress notification to the client.
  */
 public final class McpProgress {
     private final McpSession session;
+    private final SseSink sseSink;
+
     private int total;
     private int tokenInt;
     private String token;
     private boolean isSending;
 
     McpProgress(McpSession session) {
+        Objects.requireNonNull(session, "session is null");
         this.session = session;
+        this.sseSink = null;
+        this.token = "";
+    }
+
+    McpProgress(SseSink sseSink) {
+        Objects.requireNonNull(sseSink, "sseSink is null");
+        this.session = null;
+        this.sseSink = sseSink;
         this.token = "";
     }
 
@@ -50,7 +66,14 @@ public void send(int progress) {
             return;
         }
         if (isSending) {
-            session.send(McpJsonRpc.toJson(this, progress));
+            if (sseSink != null) {
+                sseSink.emit(SseEvent.builder()
+                                     .name("message")
+                                     .data(McpJsonRpc.toJson(this, progress))
+                                     .build());
+            } else if (session != null) {
+                session.send(McpJsonRpc.toJson(this, progress));
+            }
         }
         if (progress >= total) {
             isSending = false;