Java连接kafka
1、maven依赖：
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.xxx.test</groupId>
<artifactId>xxx</artifactId>
<version>1.0-SNAPSHOT</version>
<inceptionYear>2008</inceptionYear>
<properties>
<scala.version>2.11.12</scala.version>
<kafka.version>0.10.2.0</kafka.version>
<!--<kafka.version>1.1.0</kafka.version>-->
</properties> <repositories>
<repository>
<id>scala-tools.org</id>
<name>Scala-Tools Maven2 Repository</name>
<url>http://scala-tools.org/repo-releases</url>
</repository>
</repositories> <pluginRepositories>
<pluginRepository>
<id>scala-tools.org</id>
<name>Scala-Tools Maven2 Repository</name>
<url>http://scala-tools.org/repo-releases</url>
</pluginRepository>
</pluginRepositories> <dependencies> <!-- https://mvnrepository.com/artifact/org.apache.kafka/kafka -->
<dependency>
<groupId>org.apache.kafka</groupId>
<artifactId>kafka_2.12</artifactId>
<version>${kafka.version}</version>
</dependency> <!-- https://mvnrepository.com/artifact/org.apache.kafka/kafka-clients -->
<dependency>
<groupId>org.apache.kafka</groupId>
<artifactId>kafka-clients</artifactId>
<version>${kafka.version}</version>
</dependency> </dependencies> <build>
<sourceDirectory>src/main/scala</sourceDirectory>
<testSourceDirectory>src/test/scala</testSourceDirectory>
<plugins>
<plugin>
<groupId>org.scala-tools</groupId>
<artifactId>maven-scala-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>compile</goal>
<goal>testCompile</goal>
</goals>
</execution>
</executions>
<configuration>
<scalaVersion>${scala.version}</scalaVersion>
<args>
<arg>-target:jvm-1.8</arg>
</args>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-eclipse-plugin</artifactId>
<configuration>
<downloadSources>true</downloadSources>
<buildcommands>
<buildcommand>ch.epfl.lamp.sdt.core.scalabuilder</buildcommand>
</buildcommands>
<additionalProjectnatures>
<projectnature>ch.epfl.lamp.sdt.core.scalanature</projectnature>
</additionalProjectnatures>
<classpathContainers>
<classpathContainer>org.eclipse.jdt.launching.JRE_CONTAINER</classpathContainer>
<classpathContainer>ch.epfl.lamp.sdt.launching.SCALA_CONTAINER</classpathContainer>
</classpathContainers>
</configuration>
</plugin> <plugin>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<appendAssemblyId>false</appendAssemblyId>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
<archive>
<manifest>
<!-- 此处指定main方法入口的class -->
<mainClass></mainClass>
</manifest>
</archive>
</configuration>
<executions>
<execution>
<id>make-assembly</id>
<phase>package</phase>
<goals>
<goal>assembly</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build> <reporting>
<plugins> <plugin>
<groupId>org.scala-tools</groupId>
<artifactId>maven-scala-plugin</artifactId>
<configuration>
<scalaVersion>${scala.version}</scalaVersion>
</configuration>
</plugin> </plugins>
</reporting>
</project>
2、Java代码：
import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer; import java.util.Collections;
import java.util.Properties; public class MyConsumer{ private final static String TOPIC = "test_topic";
private final static String KAFKA_SERVER_URL = "10.31.7.200";
private final static String KAFKA_SERVER_PORT = "9092";
public static final String HOST_NAME = KAFKA_SERVER_URL; public static KafkaConsumer<Integer, String> getConsumer() {
KafkaConsumer<Integer, String> consumer;
Properties props = new Properties();
props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, KAFKA_SERVER_URL + ":" + KAFKA_SERVER_PORT);
props.put(ConsumerConfig.GROUP_ID_CONFIG, "DemoConsumer");
props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, "true");
props.put(ConsumerConfig.AUTO_COMMIT_INTERVAL_MS_CONFIG, "1000");
props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, "30000");
props.put("host.name",HOST_NAME); props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer"); // props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.IntegerDeserializer");
// props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");
// props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.connect.json.JsonConverter"); consumer = new KafkaConsumer<Integer, String>(props);
return consumer;
} public static void main(String[] args) {
KafkaConsumer<Integer, String> consumer = getConsumer();
consumer.subscribe(Collections.singletonList(TOPIC));
ConsumerRecords<Integer, String> records ; records = consumer.poll(1000); for (ConsumerRecord<Integer, String> record : records) {
System.out.println("Received message: (" + record.key() + ", " + record.value() + ") at offset " + record.offset());
}
}
}
3、可能的报错：
需要设置 props.put("host.name",ip);
org.apache.kafka.common.errors.TimeoutException
这个报错需要检查k/v的序列化类，要求序列化类是org.apache.kafka.common.serialization.Deserializer的子类
Exception in thread "main" org.apache.kafka.common.errors.SerializationException: Error deserializing key/value for partition event_topic-0 at offset 161529729
Caused by: org.apache.kafka.common.errors.SerializationException: Size of data received by IntegerDeserializer is not 4
1、需要设置 value.deserializer 的值
Exception in thread "main" org.apache.kafka.common.config.ConfigException: Missing required configuration "value.deserializer" which has no default value.
at org.apache.kafka.common.config.ConfigDef.parse(ConfigDef.java:436)
at org.apache.kafka.common.config.AbstractConfig.<init>(AbstractConfig.java:56)
at org.apache.kafka.common.config.AbstractConfig.<init>(AbstractConfig.java:63)
at org.apache.kafka.clients.consumer.ConsumerConfig.<init>(ConsumerConfig.java:426)
at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:597)
at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:579)
at com.fumi.test.MyConsumer2.get(MyConsumer2.java:46)
at com.fumi.test.MyConsumer2.main(MyConsumer2.java:56)
2、k/v的 序列化类 org.apache.kafka.connect.json.JsonConverter 不是 org.apache.kafka.common.serialization.Deserializer 的子类，所以报错了。
Exception in thread "main" org.apache.kafka.common.KafkaException: Failed to construct kafka consumer
at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:717)
at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:597)
at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:579)
at com.fumi.test.MyConsumer2.get(MyConsumer2.java:46)
at com.fumi.test.MyConsumer2.main(MyConsumer2.java:56)
Caused by: org.apache.kafka.common.KafkaException: org.apache.kafka.connect.json.JsonConverter is not an instance of org.apache.kafka.common.serialization.Deserializer
at org.apache.kafka.common.config.AbstractConfig.getConfiguredInstance(AbstractConfig.java:205)
at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:645)
... 4 more
这个报错也是类似
Exception in thread "main" org.apache.kafka.common.KafkaException: Failed to construct kafka consumer
at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:717)
at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:597)
at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:579)
at com.fumi.test.MyConsumer2.get(MyConsumer2.java:46)
at com.fumi.test.MyConsumer2.main(MyConsumer2.java:56)
Caused by: org.apache.kafka.common.KafkaException: org.apache.kafka.common.serialization.StringSerializer is not an instance of org.apache.kafka.common.serialization.Deserializer
at org.apache.kafka.common.config.AbstractConfig.getConfiguredInstance(AbstractConfig.java:205)
at org.apache.kafka.clients.consumer.KafkaConsumer.<init>(KafkaConsumer.java:637)
... 4 more
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