[英]Java Kafka Consumer noClassDefFoundError
I am learning using a test Kafka consumer & producer however facing below error. 我正在学习使用测试卡夫卡消费者和生产者,但是面临以下错误。
Kafka consumer program: 卡夫卡消费者计划:
package kafka001;
import java.util.Arrays;
import java.util.Properties;
import java.util.Scanner;
import org.apache.kafka.clients.consumer.*;
import org.apache.kafka.common.errors.WakeupException;
public class ConsumerApp {
private static Scanner in;
private static boolean stop = false;
public static void main(String[] args) throws Exception {
System.out.println(args[0] + args.length);
if (args.length != 2) {
System.err.printf("Usage: %s <topicName> <groupId>\n");
System.exit(-1);
}
in = new Scanner(System.in);
String topicName = args[0];
String groupId = args[1];
ConsumerThread consumerRunnable = new ConsumerThread(topicName, groupId);
consumerRunnable.start();
//System.out.println("Here");
String line = "";
while (!line.equals("exit")) {
line = in.next();
}
consumerRunnable.getKafkaConsumer().wakeup();
System.out.println("Stopping consumer now.....");
consumerRunnable.join();
}
private static class ConsumerThread extends Thread{
private String topicName;
private String groupId;
private KafkaConsumer<String,String> kafkaConsumer;
public ConsumerThread(String topicName, String groupId){
//System.out.println("inside ConsumerThread constructor");
this.topicName = topicName;
this.groupId = groupId;
}
public void run() {
//System.out.println("inside run");
// Setup Kafka producer properties
Properties configProperties = new Properties();
configProperties.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "aup7727s.unix.anz:9092");
configProperties.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
configProperties.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer");
configProperties.put(ConsumerConfig.GROUP_ID_CONFIG, groupId);
configProperties.put(ConsumerConfig.CLIENT_ID_CONFIG, "simple");
// subscribe to topic
kafkaConsumer = new KafkaConsumer<String, String>(configProperties);
kafkaConsumer.subscribe(Arrays.asList(topicName));
// Get/process messages from topic and print it to console
try {while(true) {
ConsumerRecords<String, String> records = kafkaConsumer.poll(100);
for (ConsumerRecord<String, String> record : records)
System.out.println(record.value());
}
} catch(WakeupException ex) {
System.out.println("Exception caught " + ex.getMessage());
}finally {
kafkaConsumer.close();
System.out.println("After closing KafkaConsumer");
}
}
public KafkaConsumer<String,String> getKafkaConsumer(){
return this.kafkaConsumer;
}
}
}
When I compile the code, I am noticing following class files: 编译代码时,我注意到以下类文件:
ConsumerApp$ConsumerThread.class and ConsumerApp.class ConsumerApp $ ConsumerThread.class和ConsumerApp.class
I've generated jar file named ConsumerApp.jar through eclipse and when I run this in Hadoop cluster, I get noclassdeffound error as below: 我已经通过eclipse生成了一个名为ConsumerApp.jar的jar文件,当我在Hadoop集群中运行它时,出现noclassdeffound错误,如下所示:
java -cp ConsumerApp.jar kafka001/ConsumerApp console1 group1
or
hadoop jar ConsumerApp.jar console1 group1
Exception in thread "main" java.lang.NoClassDefFoundError: org.apache.kafka.common.errors.WakeupException
at kafka001.ConsumerApp.main(ConsumerApp.java:24)
Caused by: java.lang.ClassNotFoundException: org.apache.kafka.common.errors.WakeupException
at java.net.URLClassLoader.findClass(URLClassLoader.java:607)
at java.lang.ClassLoader.loadClassHelper(ClassLoader.java:846)
at java.lang.ClassLoader.loadClass(ClassLoader.java:825)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:325)
at java.lang.ClassLoader.loadClass(ClassLoader.java:805)
... 1 more
I am using Eclipse to compile, maven build and generate jar file. 我正在使用Eclipse进行编译,maven构建和生成jar文件。 Line number 24 correspond to creation of ConsumerThread instance.
行号24对应于ConsumerThread实例的创建。
I am unable to resolve if its due to ConsumerThread class name being incorrectly saved (Class file generated as ConsumerApp$ConsumerThread.class instead of ConsumerThread.class) ? 我是否无法解析是否由于ConsumerThread类名称的错误保存(生成为ConsumerApp $ ConsumerThread.class而不是ConsumerThread.class的类文件)? or something to be taken care while generating jar file ?
或生成jar文件时要注意的事项?
Since I can't view the entire project, I would try this: Right click on the project -> go to Maven 2 tools -> click generate artifacts (check for updates). 由于无法查看整个项目,因此我将尝试以下操作:右键单击项目->转到Maven 2工具->单击生成工件(检查更新)。 That should create any missing dependencies.
那应该创建任何丢失的依赖项。 Also make sure you check out other similar posts that may resolve your issue like this .
另外,还要确保你检查出可能解决您的问题像其他类似的帖子这个 。
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