From: Kai Moritz <kai@juplo.de>
Date: Tue, 1 Apr 2025 21:07:38 +0000 (+0200)
Subject: Vorlage für das Live-Coding zum `simple-consumer`
X-Git-Tag: grundlagen/simple-consumer--livecoding--2025-04-signal-spickzettel
X-Git-Url: http://juplo.de/gitweb/?a=commitdiff_plain;h=8b523af7caf98711fe2d2eba26babd949f400176;p=demos%2Fkafka%2Ftraining

Vorlage für das Live-Coding zum `simple-consumer`
---

diff --git a/src/main/java/de/juplo/kafka/ExampleConsumer.java b/src/main/java/de/juplo/kafka/ExampleConsumer.java
index 7be827e..b02d502 100644
--- a/src/main/java/de/juplo/kafka/ExampleConsumer.java
+++ b/src/main/java/de/juplo/kafka/ExampleConsumer.java
@@ -16,19 +16,19 @@ import java.util.Properties;
 @Slf4j
 public class ExampleConsumer
 {
-  private final String id;
-  private final String topic;
-  private final Consumer<String, String> consumer;
+  private String id;
+  private String topic;
+  private Consumer<String, String> consumer;
 
-  private volatile boolean running = false;
   private long consumed = 0;
 
-  public ExampleConsumer(
-    String broker,
-    String topic,
-    String groupId,
-    String clientId)
+  public static void main(String[] args) throws Exception
   {
+    String broker = "localhost:9092";
+    String topic = "test";
+    String groupId = "my-group";
+    String clientId = "DEV";
+
     Properties props = new Properties();
     props.put("bootstrap.servers", broker);
     props.put("group.id", groupId); // ID für die Offset-Commits
@@ -36,28 +36,26 @@ public class ExampleConsumer
     props.put("key.deserializer", StringDeserializer.class.getName());
     props.put("value.deserializer", StringDeserializer.class.getName());
 
-    this.id = clientId;
-    this.topic = topic;
-    consumer = new KafkaConsumer<>(props);
-  }
+    Consumer<String, String> consumer = new KafkaConsumer<>(props);
 
+    String id = clientId;
+    long consumed = 0;
 
-  public void run()
-  {
     try
     {
       log.info("{} - Subscribing to topic {}", id, topic);
       consumer.subscribe(Arrays.asList(topic));
-      running = true;
 
       while (true)
       {
         ConsumerRecords<String, String> records = consumer.poll(Duration.ofSeconds(1));
 
-        log.info("{} - Received {} messages", id, records.count());
         for (ConsumerRecord<String, String> record : records)
         {
-          handleRecord(
+          consumed++;
+          log.info(
+            "{} - partition={}-{}, offset={}: {}={}",
+            id,
             record.topic(),
             record.partition(),
             record.offset(),
@@ -66,76 +64,10 @@ public class ExampleConsumer
         }
       }
     }
-    catch(WakeupException e)
-    {
-      log.info("{} - Consumer was signaled to finish its work", id);
-    }
-    catch(Exception e)
-    {
-      log.error("{} - Unexpected error, unsubscribing!", id, e);
-      consumer.unsubscribe();
-    }
     finally
     {
-      log.info("{} - Closing the KafkaConsumer", id);
-      consumer.close();
       log.info("{}: Consumed {} messages in total, exiting!", id, consumed);
-      running = false;
     }
   }
-
-  private void handleRecord(
-    String topic,
-    Integer partition,
-    Long offset,
-    String key,
-    String value)
-  {
-    consumed++;
-    log.info("{} - partition={}-{}, offset={}: {}={}", id, topic, partition, offset, key, value);
-  }
-
-
-  public static void main(String[] args) throws Exception
-  {
-    if (args.length != 4)
-    {
-      log.error("Four arguments required!");
-      log.error("args[0]: Broker-Address");
-      log.error("args[1]: Topic");
-      log.error("args[2]: Group-ID");
-      log.error("args[3]: Unique Client-ID");
-      System.exit(1);
-      return;
-    }
-
-
-    log.info(
-      "Running ExampleConsumer: broker={}, topic={}, group-id={}, client-id={}",
-      args[0],
-      args[1],
-      args[2],
-      args[3]);
-
-    ExampleConsumer instance = new ExampleConsumer(args[0], args[1], args[2], args[3]);
-
-    Runtime.getRuntime().addShutdownHook(new Thread(() ->
-    {
-      instance.consumer.wakeup();
-
-      while (instance.running)
-      {
-        log.info("Waiting for main-thread...");
-        try
-        {
-          Thread.sleep(1000);
-        }
-        catch (InterruptedException e) {}
-      }
-      log.info("Shutdown completed.");
-    }));
-
-    instance.run();
-  }
 }