Docker Kafka Producer java.lang.ClassNotFoundException

Question

I'm trying to run my kafka project on docker. If I run this project on my local it works correctly but If I run on docker I got this error message

   Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/kafka/clients/producer/Producer
        at com.kafka.App.main(App.java:14)
Caused by: java.lang.ClassNotFoundException: org.apache.kafka.clients.producer.Producer
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 1 more

I'm not sure but it looks like can't load dependencies from pom.xml.

Here is my Dockerfile

FROM maven:3.5-jdk-8 as maven
WORKDIR /app
COPY ./pom.xml ./pom.xml
RUN mvn dependency:go-offline -B
COPY ./src ./src
RUN mvn package && cp target/kafka-producer-*.jar app.jar
RUN apk add --no-cache bash
WORKDIR /app
COPY --from=maven /app/app.jar ./app.jar
CMD ["java", "-jar", "/app/app.jar"]

And last thing App:14 creating new instance from SimpleProducer class and the error line is

import com.kafka.Interfaces.IKafkaConstants;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.Producer;      ***HERE***
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.serialization.LongSerializer;
import org.apache.kafka.common.serialization.StringSerializer;
import java.util.Properties;

public class SimpleProducer {

You should pre-package your application (with all its dependencies) in a single jar and use this jar to build your container... — Turing85
– Turing85, Commented Jun 17, 2019 at 20:15
Yeah actually I'm doing as you said with "mvn clean package" and then I'm building it "docker build . -t foobar" @Turing85 — more
– more, Commented Jun 17, 2019 at 21:23
That doesn't mean that your JAR contains all the declared dependencies. You need to create an uber jar — OneCricketeer
– OneCricketeer, Commented Jun 18, 2019 at 0:16

OneCricketeer · Accepted Answer · 2019-06-18 18:49:35Z

1

Based on the error, it seems like your JAR doesn't contain your declared dependencies.

You should get a similar error doing java -jar "locally", and you can get around the error using the shade plugin, for example to make an uber jar.

Or, I would suggest using jib-maven-plugin to build the container, which I beleive does put all declare dependencies into the container image, and you don't need a Dockerfile. (I have no affiliation)

edited Jun 18, 2019 at 18:49

answered Jun 18, 2019 at 18:37

OneCricketeer

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