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[demos/kafka/training] / src / main / java / de / juplo / kafka / SimpleConsumer.java

diff --git a/src/main/java/de/juplo/kafka/SimpleConsumer.java b/src/main/java/de/juplo/kafka/SimpleConsumer.java
index e4d9697..8e557c2 100644 (file)
--- a/src/main/java/de/juplo/kafka/SimpleConsumer.java
+++ b/src/main/java/de/juplo/kafka/SimpleConsumer.java
@@ -1,131 +1,80 @@
 package de.juplo.kafka;
 
+import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import org.apache.kafka.clients.consumer.Consumer;
 import org.apache.kafka.clients.consumer.ConsumerRecord;
 import org.apache.kafka.clients.consumer.ConsumerRecords;
-import org.apache.kafka.clients.consumer.KafkaConsumer;
 import org.apache.kafka.common.errors.WakeupException;
-import org.apache.kafka.common.serialization.StringDeserializer;
 
 import java.time.Duration;
 import java.util.Arrays;
-import java.util.Properties;
-import java.util.concurrent.locks.Condition;
-import java.util.concurrent.locks.Lock;
-import java.util.concurrent.locks.ReentrantLock;
+import java.util.concurrent.Callable;
 
 
 @Slf4j
-public class SimpleConsumer
+@RequiredArgsConstructor
+public class SimpleConsumer implements Callable<Integer>
 {
-  private long consumed = 0;
-  private KafkaConsumer<String, String> consumer;
-  private Lock lock = new ReentrantLock();
-  private Condition stopped = lock.newCondition();
-
-
-  public SimpleConsumer()
-  {
-    // tag::create[]
-    Properties props = new Properties();
-    props.put("bootstrap.servers", ":9092");
-    props.put("group.id", "my-consumer"); // << Used for Offset-Commits
-    // end::create[]
-    props.put("auto.offset.reset", "earliest");
-    // tag::create[]
-    props.put("key.deserializer", StringDeserializer.class.getName());
-    props.put("value.deserializer", StringDeserializer.class.getName());
+  private final String id;
+  private final String topic;
+  private final Consumer<String, String> consumer;
 
-    KafkaConsumer<String, String> consumer = new KafkaConsumer<>(props);
-    // end::create[]
-    this.consumer = consumer;
-  }
+  private long consumed = 0;
 
 
-  public void run()
+  @Override
+  public Integer call()
   {
-    String id = "C";
-
     try
     {
-      log.info("{} - Subscribing to topic test", id);
-      consumer.subscribe(Arrays.asList("test"));
+      log.info("{} - Subscribing to topic {}", id, topic);
+      consumer.subscribe(Arrays.asList(topic));
 
-      // tag::loop[]
       while (true)
       {
         ConsumerRecords<String, String> records =
             consumer.poll(Duration.ofSeconds(1));
 
-        // Do something with the data...
-        // end::loop[]
         log.info("{} - Received {} messages", id, records.count());
         for (ConsumerRecord<String, String> record : records)
         {
-          consumed++;
-          log.info(
-              "{} - {}: {}/{} - {}={}",
-              id,
-              record.offset(),
-              record.topic(),
-              record.partition(),
-              record.key(),
-              record.value()
-          );
+          handleRecord(
+            record.topic(),
+            record.partition(),
+            record.offset(),
+            record.key(),
+            record.value());
         }
-        // tag::loop[]
       }
-      // end::loop[]
     }
     catch(WakeupException e)
     {
-      log.info("{} - RIIING!", id);
+      log.info("{} - Consumer was signaled to finish its work", id);
+      return 0;
     }
     catch(Exception e)
     {
-      log.error("{} - Unexpected error: {}", id, e.toString());
+      log.error("{} - Unexpected error: {}, unsubscribing!", id, e.toString());
+      consumer.unsubscribe();
+      return 1;
     }
     finally
     {
-      this.lock.lock();
-      try
-      {
-        log.info("{} - Closing the KafkaConsumer", id);
-        consumer.close();
-        log.info("C - DONE!");
-        stopped.signal();
-      }
-      finally
-      {
-        this.lock.unlock();
-        log.info("{}: Consumed {} messages in total, exiting!", id, consumed);
-      }
+      log.info("{} - Closing the KafkaConsumer", id);
+      consumer.close();
+      log.info("{}: Consumed {} messages in total, exiting!", id, consumed);
     }
   }
 
-
-  public static void main(String[] args) throws Exception
+  private void handleRecord(
+    String topic,
+    Integer partition,
+    Long offset,
+    String key,
+    Message value)
   {
-    SimpleConsumer instance = new SimpleConsumer();
-
-    Runtime.getRuntime().addShutdownHook(new Thread(() ->
-    {
-      instance.lock.lock();
-      try
-      {
-        instance.consumer.wakeup();
-        instance.stopped.await();
-      }
-      catch (InterruptedException e)
-      {
-        log.warn("Interrrupted while waiting for the consumer to stop!", e);
-      }
-      finally
-      {
-        instance.lock.unlock();
-      }
-    }));
-
-    instance.run();
+    consumed++;
+    log.info("{} - {}: {}/{} - {}={}", id, offset, topic, partition, key, value);
   }
 }