【flink】之如何消费kafka数据？

为了编写一个使用Apache Flink来读取Apache Kafka消息的示例，我们需要确保我们的环境已经安装了Flink和Kafka，并且它们都能正常运行。此外，我们还需要在项目中引入相应的依赖库。以下是一个详细的步骤指南，包括依赖添加、代码编写和执行说明。

1.环境准备

确保你已经安装了Apache Kafka和Apache Flink，并且Kafka正在运行。Kafka的默认端口是9092，而Zookeeper（Kafka依赖的服务）的默认端口是2181

2.Maven项目设置

创建一个新的Maven项目，并在pom.xml中添加以下依赖：

<dependencies>  <!-- Flink dependencies -->  <dependency>  <groupId>org.apache.flink</groupId>  <artifactId>flink-streaming-java_2.12</artifactId>  <version>1.13.2</version>  </dependency>  <dependency>  <groupId>org.apache.flink</groupId>  <artifactId>flink-connector-kafka_2.12</artifactId>  <version>1.13.2</version>  </dependency>  <!-- Kafka client dependency -->  <dependency>  <groupId>org.apache.kafka</groupId>  <artifactId>kafka-clients</artifactId>  <version>2.8.0</version>  </dependency>  <!-- Logging -->  <dependency>  <groupId>org.slf4j</groupId>  <artifactId>slf4j-log4j12</artifactId>  <version>1.7.30</version>  </dependency>  
</dependencies>

注意：请根据你使用的Scala或Java版本以及Flink和Kafka的版本调整上述依赖。

3.编写Flink Kafka Consumer代码

import org.apache.flink.api.common.functions.MapFunction;  
import org.apache.flink.streaming.api.datastream.DataStream;  
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;  
import org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer;  import java.util.Properties;  public class FlinkKafkaConsumerDemo {  public static void main(String[] args) throws Exception {  // 设置执行环境  final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();  // Kafka消费者属性  Properties props = new Properties();  props.put("bootstrap.servers", "localhost:9092");  props.put("group.id", "test-group");  props.put("enable.auto.commit", "true");  props.put("auto.commit.interval.ms", "1000");  props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");  props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");  // 创建Kafka消费者  FlinkKafkaConsumer<String> myConsumer = new FlinkKafkaConsumer<>(  "input-topic", // Kafka topic  new SimpleStringSchema(), // 反序列化器  props);  // 添加数据源  DataStream<String> stream = env.addSource(myConsumer);  // 数据处理  stream.map(new MapFunction<String, String>() {  @Override  public String map(String value) throws Exception {  return "Received: " + value;  }  }).print();  // 执行流程序  env.execute("Flink Kafka Consumer Example");  }  // 简单的字符串反序列化器  public static final class SimpleStringSchema implements DeserializationSchema<String> {  @Override  public String deserialize(byte[] message) throws IOException {  return new String(message, "UTF-8");  }  @Override  public boolean isEndOfStream(String nextElement) {  return false;  }  @Override  public TypeInformation<String> getProducedType() {  return BasicTypeInfo.STRING_TYPE_INFO;  }  }  
}