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