From 917ddc7b598e1c7e361dbba8192e304962367952 Mon Sep 17 00:00:00 2001
From: Kai Moritz <kai@juplo.de>
Date: Fri, 4 Nov 2022 12:59:20 +0100
Subject: [PATCH] SimpleConsumer auf JSON-Nachrichten umgestellt

---
 src/main/java/de/juplo/kafka/Message.java     |  9 ++++++
 .../java/de/juplo/kafka/MessageAddNumber.java | 19 ++++++++++++
 .../de/juplo/kafka/MessageCalculateSum.java   | 16 ++++++++++
 .../java/de/juplo/kafka/SimpleConsumer.java   |  6 ++--
 src/main/resources/application.yml            |  5 +++-
 src/test/java/de/juplo/kafka/MessageTest.java | 29 +++++++++++++++++++
 6 files changed, 80 insertions(+), 4 deletions(-)
 create mode 100644 src/main/java/de/juplo/kafka/Message.java
 create mode 100644 src/main/java/de/juplo/kafka/MessageAddNumber.java
 create mode 100644 src/main/java/de/juplo/kafka/MessageCalculateSum.java
 create mode 100644 src/test/java/de/juplo/kafka/MessageTest.java

diff --git a/src/main/java/de/juplo/kafka/Message.java b/src/main/java/de/juplo/kafka/Message.java
new file mode 100644
index 0000000..e4999b7
--- /dev/null
+++ b/src/main/java/de/juplo/kafka/Message.java
@@ -0,0 +1,9 @@
+package de.juplo.kafka;
+
+
+public abstract class Message
+{
+  public enum Type {ADD, CALC}
+
+  public abstract Type getType();
+}
diff --git a/src/main/java/de/juplo/kafka/MessageAddNumber.java b/src/main/java/de/juplo/kafka/MessageAddNumber.java
new file mode 100644
index 0000000..c024b65
--- /dev/null
+++ b/src/main/java/de/juplo/kafka/MessageAddNumber.java
@@ -0,0 +1,19 @@
+package de.juplo.kafka;
+
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import lombok.Data;
+
+
+@Data
+@JsonIgnoreProperties(ignoreUnknown = true)
+public class MessageAddNumber extends Message
+{
+  private Integer next;
+
+
+  @Override
+  public Type getType()
+  {
+    return Type.ADD;
+  }
+}
diff --git a/src/main/java/de/juplo/kafka/MessageCalculateSum.java b/src/main/java/de/juplo/kafka/MessageCalculateSum.java
new file mode 100644
index 0000000..afc5a39
--- /dev/null
+++ b/src/main/java/de/juplo/kafka/MessageCalculateSum.java
@@ -0,0 +1,16 @@
+package de.juplo.kafka;
+
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+import lombok.Data;
+
+
+@Data
+@JsonIgnoreProperties(ignoreUnknown = true)
+public class MessageCalculateSum extends Message
+{
+  @Override
+  public Type getType()
+  {
+    return Type.CALC;
+  }
+}
diff --git a/src/main/java/de/juplo/kafka/SimpleConsumer.java b/src/main/java/de/juplo/kafka/SimpleConsumer.java
index 0e37686..7f94371 100644
--- a/src/main/java/de/juplo/kafka/SimpleConsumer.java
+++ b/src/main/java/de/juplo/kafka/SimpleConsumer.java
@@ -17,7 +17,7 @@ public class SimpleConsumer implements Runnable
 {
   private final String id;
   private final String topic;
-  private final Consumer<String, String> consumer;
+  private final Consumer<String, Message> consumer;
 
   private long consumed = 0;
 
@@ -32,11 +32,11 @@ public class SimpleConsumer implements Runnable
 
       while (true)
       {
-        ConsumerRecords<String, String> records =
+        ConsumerRecords<String, Message> records =
             consumer.poll(Duration.ofSeconds(1));
 
         log.info("{} - Received {} messages", id, records.count());
-        for (ConsumerRecord<String, String> record : records)
+        for (ConsumerRecord<String, Message> record : records)
         {
           consumed++;
           log.info(
diff --git a/src/main/resources/application.yml b/src/main/resources/application.yml
index d524e5f..07d0625 100644
--- a/src/main/resources/application.yml
+++ b/src/main/resources/application.yml
@@ -30,10 +30,13 @@ spring:
       auto-offset-reset: earliest
       auto-commit-interval: 5s
       key-deserializer: org.apache.kafka.common.serialization.StringDeserializer
-      value-deserializer: org.apache.kafka.common.serialization.StringDeserializer
+      value-deserializer: org.springframework.kafka.support.serializer.JsonDeserializer
       properties:
         partition.assignment.strategy: org.apache.kafka.clients.consumer.StickyAssignor
         metadata.max.age.ms: 1000
+        spring.json.type.mapping: >
+          ADD:de.juplo.kafka.MessageAddNumber,
+          CALC:de.juplo.kafka.MessageCalculateSum
 logging:
   level:
     root: INFO
diff --git a/src/test/java/de/juplo/kafka/MessageTest.java b/src/test/java/de/juplo/kafka/MessageTest.java
new file mode 100644
index 0000000..82116f4
--- /dev/null
+++ b/src/test/java/de/juplo/kafka/MessageTest.java
@@ -0,0 +1,29 @@
+package de.juplo.kafka;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+
+public class MessageTest
+{
+  ObjectMapper mapper = new ObjectMapper();
+
+  @Test
+  @DisplayName("Deserialize a MessageAddNumber message")
+  public void testDeserializeMessageAddNumber()
+  {
+    Assertions.assertDoesNotThrow(() -> mapper.readValue("{\"next\":42}", MessageAddNumber.class));
+    Assertions.assertDoesNotThrow(() -> mapper.readValue("{\"number\":666,\"next\":42}", MessageAddNumber.class));
+  }
+
+  @Test
+  @DisplayName("Deserialize a MessageCalculateSum message")
+  public void testDeserializeMessageCalculateSum() throws JsonProcessingException
+  {
+    Assertions.assertDoesNotThrow(() -> mapper.readValue("{}", MessageCalculateSum.class));
+    Assertions.assertDoesNotThrow(() -> mapper.readValue("{\"number\":666}", MessageCalculateSum.class));
+  }
+}
-- 
2.20.1