[ISSUE #6752] fix: encode SSE events as UTF-8

shenyu-plugin/shenyu-plugin-mcp-server/src/main/java/org/apache/shenyu/plugin/mcp/server/transport/SseEventFormatter.java

@@ -23,6 +23,7 @@
 import org.springframework.http.codec.ServerSentEvent;
 import org.springframework.web.server.ServerWebExchange;
 
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 
 /**
@@ -73,7 +74,7 @@ public static DataBuffer formatEvent(final ServerSentEvent<?> event, final Serve
         String formattedEvent = sseData.toString();
         LOG.debug("Formatted SSE event: {}", formattedEvent.trim());
 
-        return exchange.getResponse().bufferFactory().wrap(formattedEvent.getBytes());
+        return exchange.getResponse().bufferFactory().wrap(formattedEvent.getBytes(StandardCharsets.UTF_8));
     }
 
     /**
@@ -86,6 +87,6 @@ public static DataBuffer formatEvent(final ServerSentEvent<?> event, final Serve
     public static DataBuffer formatComment(final String comment, final ServerWebExchange exchange) {
         String formattedComment = ": " + comment + "\n\n";
         LOG.debug("Formatted SSE comment: {}", formattedComment.trim());
-        return exchange.getResponse().bufferFactory().wrap(formattedComment.getBytes());
+        return exchange.getResponse().bufferFactory().wrap(formattedComment.getBytes(StandardCharsets.UTF_8));
     }
 }

shenyu-plugin/shenyu-plugin-mcp-server/src/test/java/org/apache/shenyu/plugin/mcp/server/transport/SseEventFormatterTest.java

@@ -0,0 +1,67 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.shenyu.plugin.mcp.server.transport;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferUtils;
+import org.springframework.http.codec.ServerSentEvent;
+import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
+import org.springframework.mock.web.server.MockServerWebExchange;
+
+import java.nio.charset.StandardCharsets;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+/**
+ * Test cases for {@link SseEventFormatter}.
+ */
+final class SseEventFormatterTest {
+
+    @Test
+    void testFormatEventUsesUtf8() {
+        MockServerWebExchange exchange = MockServerWebExchange.from(MockServerHttpRequest.get("/mcp/sse").build());
+        ServerSentEvent<String> event = ServerSentEvent.builder("{\"message\":\"你好，世界\"}")
+                .event("message")
+                .build();
+
+        DataBuffer buffer = SseEventFormatter.formatEvent(event, exchange);
+
+        assertArrayEquals("event: message\ndata: {\"message\":\"你好，世界\"}\n\n".getBytes(StandardCharsets.UTF_8),
+                readAndRelease(buffer));
+    }
+
+    @Test
+    void testFormatCommentUsesUtf8() {
+        MockServerWebExchange exchange = MockServerWebExchange.from(MockServerHttpRequest.get("/mcp/sse").build());
+
+        DataBuffer buffer = SseEventFormatter.formatComment("保持连接", exchange);
+
+        assertArrayEquals(": 保持连接\n\n".getBytes(StandardCharsets.UTF_8), readAndRelease(buffer));
+    }
+
+    private static byte[] readAndRelease(final DataBuffer buffer) {
+        try {
+            byte[] bytes = new byte[buffer.readableByteCount()];
+            buffer.read(bytes);
+            return bytes;
+        } finally {
+            DataBufferUtils.release(buffer);
+        }
+    }
+}