🎉 add kafka demo

src/main/java/com/darkness/engine/kafkademo/KafkaDemoController.java

@@ -0,0 +1,19 @@
+package com.darkness.engine.kafkademo;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+@RequestMapping("/kafka")
+public class KafkaDemoController {
+
+    @Autowired
+    private KafkaDemoService kafkaDemoService;
+
+    @PostMapping("/demo")
+    public void sendMessage() {
+        kafkaDemoService.sendMessage("my-topic", "Hello, Kafka!");
+    }
+}

src/main/java/com/darkness/engine/kafkademo/KafkaDemoService.java

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+package com.darkness.engine.kafkademo;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.kafka.annotation.KafkaListener;
+import org.springframework.kafka.core.KafkaTemplate;
+import org.springframework.stereotype.Service;
+
+@Service
+public class KafkaDemoService {
+
+    @Autowired
+    private KafkaTemplate<String, String> kafkaTemplate;
+
+    public void sendMessage(String topic, String message) {
+        kafkaTemplate.send(topic, message).addCallback(
+                success -> System.out.println("Message sent successfully!"),
+                failure -> System.err.println("Failed to send message: " + failure.getMessage())
+        );
+    }
+
+    @KafkaListener(topics = "my-topic", groupId = "darkness-group")
+    public void consume(String message) {
+        System.out.println("Received message: " + message);
+    }
+}
+