Apache Kafka + Apache Camel 集成 + POC 问题 + java.util.Hashtable.put(Hashtable.java:459) 处的 java.lang.NullPointerException

Question

This is my route builder. Here i am trying to insert data from my file to topic.Later, i am passing through my main method and using camel context i am running it. I have tried several codes but none helped me. i am working on POC of Apache kafka - Camel.

public class SimpleRouteBuilder extends RouteBuilder {

    @Override
    public void configure() throws Exception {

        String topicName = "test120";
        String kafkaServer = "kafka:localhost:9092";
        String zooKeeperHost = "zookeeperHost=localhost&zookeeperPort=2181";
        String serializerClass = "serializerClass=kafka.serializer.StringEncoder";

        String toKafka =  "kafka:localhost:9092?topic=test120;zookeeperHost=localhost;zookeeperPort=2181;groupId=group1";


    //  toKafka = new StringBuilder().append("&").append(serializerClass).toString();

                /*new StringBuilder().append(kafkaServer).append("?").append(topicName).append("&")
                .append(zooKeeperHost).append("&").append(serializerClass).toString();*/

        from("file:C:/inbox?noop=true").to(toKafka);


    }
}

This is my pom.xml

<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/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>HelloWorld</groupId>
  <artifactId>Pallavi</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <dependencies>
      <dependency>
          <groupId>org.apache.camel</groupId>
          <artifactId>camel-core</artifactId>
          <version>2.20.1</version>
      </dependency>

      <dependency>
          <groupId>org.apache.camel</groupId>
          <artifactId>camel-kafka</artifactId>
          <version>2.20.1</version>
      </dependency>

      <dependency>
          <groupId>org.scala-lang</groupId>
          <artifactId>scala-library</artifactId>
          <version>2.11.0</version>
      </dependency>
  </dependencies>

</project>

This is my main class:

import org.apache.camel.CamelContext;
import org.apache.camel.impl.DefaultCamelContext;

public class MainApp {

    public static void main(String[] args) {
        SimpleRouteBuilder routeBuilder = new SimpleRouteBuilder();
        CamelContext ctx = new DefaultCamelContext();
        try {
            ctx.addRoutes(routeBuilder);
            ctx.start();
            Thread.sleep(5 * 60 * 1000);
            ctx.stop();
            System.out.println("hi i am working");
        }
        catch (Exception e) {
            e.printStackTrace();
        }

    }
}

error is :

java.lang.NullPointerException
    at java.util.Hashtable.put(Hashtable.java:459)
    at org.apache.camel.component.kafka.KafkaProducer.getProps(KafkaProducer.java:63)
    at org.apache.camel.component.kafka.KafkaProducer.doStart(KafkaProducer.java:89)
    at org.apache.camel.support.ServiceSupport.start(ServiceSupport.java:61)
    at org.apache.camel.util.ServiceHelper.startService(ServiceHelper.java:75)
    at org.apache.camel.impl.DeferServiceStartupListener.onCamelContextStarted(DeferServiceStartupListener.java:49)
    at org.apache.camel.impl.DefaultCamelContext.safelyStartRouteServices(DefaultCamelContext.java:3859)
    at org.apache.camel.impl.DefaultCamelContext.doStartOrResumeRoutes(DefaultCamelContext.java:3638)
    at org.apache.camel.impl.DefaultCamelContext.doStartCamel(DefaultCamelContext.java:3490)
    at org.apache.camel.impl.DefaultCamelContext.access$000(DefaultCamelContext.java:208)
    at org.apache.camel.impl.DefaultCamelContext$2.call(DefaultCamelContext.java:3249)
    at org.apache.camel.impl.DefaultCamelContext$2.call(DefaultCamelContext.java:3245)
    at org.apache.camel.impl.DefaultCamelContext.doWithDefinedClassLoader(DefaultCamelContext.java:3268)
    at org.apache.camel.impl.DefaultCamelContext.doStart(DefaultCamelContext.java:3245)
    at org.apache.camel.support.ServiceSupport.start(ServiceSupport.java:61)
    at org.apache.camel.impl.DefaultCamelContext.start(DefaultCamelContext.java:3168)
    at demo.MainApp.main(MainApp.java:13)
Picked up _JAVA_OPTIONS: -Xmx512M -Xms512M

Answer 1

I have followed the same tutorial. But initially, I could not run successfully (who using latest version of kafka server). I got following exception instead of null point exception:

org.apache.camel.FailedToCreateRouteException: Failed to create route route1 at: >>> Split[tokenize{body() using token: 
} -> [To[kafka:localhost:9092?topic=test&zookeeperHost=localhost&zookeeperPort=2181&serializerClass=kafka.serializer.StringEncoder]]] <<< in route: Route(route1)[[From[file:C:/input?noop=true]] -> [Split[toke... because of Failed to resolve endpoint: kafka://localhost:9092?serializerClass=kafka.serializer.StringEncoder&topic=test&zookeeperHost=localhost&zookeeperPort=2181 due to: Failed to resolve endpoint: kafka://localhost:9092?serializerClass=kafka.serializer.StringEncoder&topic=test&zookeeperHost=localhost&zookeeperPort=2181 due to: There are 2 parameters that couldn't be set on the endpoint. Check the uri if the parameters are spelt correctly and that they are properties of the endpoint. Unknown parameters=[{zookeeperHost=localhost, zookeeperPort=2181}]
    at org.apache.camel.model.RouteDefinition.addRoutes(RouteDefinition.java:1303)
    at org.apache.camel.model.RouteDefinition.addRoutes(RouteDefinition.java:204)
    at org.apache.camel.impl.DefaultCamelContext.startRoute(DefaultCamelContext.java:1143)
    at org.apache.camel.impl.DefaultCamelContext.startRouteDefinitions(DefaultCamelContext.java:3729)
    at org.apache.camel.impl.DefaultCamelContext.doStartCamel(DefaultCamelContext.java:3443)
    at org.apache.camel.impl.DefaultCamelContext.access$000(DefaultCamelContext.java:209)
    at org.apache.camel.impl.DefaultCamelContext$2.call(DefaultCamelContext.java:3251)
    at org.apache.camel.impl.DefaultCamelContext$2.call(DefaultCamelContext.java:3247)
    at org.apache.camel.impl.DefaultCamelContext.doWithDefinedClassLoader(DefaultCamelContext.java:3270)
    at org.apache.camel.impl.DefaultCamelContext.doStart(DefaultCamelContext.java:3247)
    at org.apache.camel.support.ServiceSupport.start(ServiceSupport.java:61)
    at org.apache.camel.impl.DefaultCamelContext.start(DefaultCamelContext.java:3163)
    at com.parane.kafka.demo.DemoApplication.main(DemoApplication.java:17)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
Caused by: org.apache.camel.ResolveEndpointFailedException: Failed to resolve endpoint: kafka://localhost:9092?serializerClass=kafka.serializer.StringEncoder&topic=test&zookeeperHost=localhost&zookeeperPort=2181 due to: Failed to resolve endpoint: kafka://localhost:9092?serializerClass=kafka.serializer.StringEncoder&topic=test&zookeeperHost=localhost&zookeeperPort=2181 due to: There are 2 parameters that couldn't be set on the endpoint. Check the uri if the parameters are spelt correctly and that they are properties of the endpoint. Unknown parameters=[{zookeeperHost=localhost, zookeeperPort=2181}]
    at org.apache.camel.impl.DefaultCamelContext.getEndpoint(DefaultCamelContext.java:758)
    at org.apache.camel.util.CamelContextHelper.getMandatoryEndpoint(CamelContextHelper.java:80)
    at org.apache.camel.model.RouteDefinition.resolveEndpoint(RouteDefinition.java:219)
    at org.apache.camel.impl.DefaultRouteContext.resolveEndpoint(DefaultRouteContext.java:115)
    at org.apache.camel.impl.DefaultRouteContext.resolveEndpoint(DefaultRouteContext.java:121)
    at org.apache.camel.model.SendDefinition.resolveEndpoint(SendDefinition.java:62)
    at org.apache.camel.model.SendDefinition.createProcessor(SendDefinition.java:56)
    at org.apache.camel.model.ProcessorDefinition.createProcessor(ProcessorDefinition.java:511)
    at org.apache.camel.model.ProcessorDefinition.createOutputsProcessorImpl(ProcessorDefinition.java:474)
    at org.apache.camel.model.ProcessorDefinition.createOutputsProcessor(ProcessorDefinition.java:441)
    at org.apache.camel.model.ProcessorDefinition.createOutputsProcessor(ProcessorDefinition.java:185)
    at org.apache.camel.model.ProcessorDefinition.createChildProcessor(ProcessorDefinition.java:204)
    at org.apache.camel.model.SplitDefinition.createProcessor(SplitDefinition.java:101)
    at org.apache.camel.model.ProcessorDefinition.makeProcessorImpl(ProcessorDefinition.java:562)
    at org.apache.camel.model.ProcessorDefinition.makeProcessor(ProcessorDefinition.java:523)
    at org.apache.camel.model.ProcessorDefinition.addRoutes(ProcessorDefinition.java:239)
    at org.apache.camel.model.RouteDefinition.addRoutes(RouteDefinition.java:1300)
    ... 17 more
Caused by: org.apache.camel.ResolveEndpointFailedException: Failed to resolve endpoint: kafka://localhost:9092?serializerClass=kafka.serializer.StringEncoder&topic=test&zookeeperHost=localhost&zookeeperPort=2181 due to: There are 2 parameters that couldn't be set on the endpoint. Check the uri if the parameters are spelt correctly and that they are properties of the endpoint. Unknown parameters=[{zookeeperHost=localhost, zookeeperPort=2181}]
    at org.apache.camel.impl.DefaultComponent.validateParameters(DefaultComponent.java:215)
    at org.apache.camel.impl.DefaultComponent.createEndpoint(DefaultComponent.java:139)
    at org.apache.camel.impl.DefaultCamelContext.getEndpoint(DefaultCamelContext.java:711)
    ... 33 more 

As mentioned by Claus Ibsen, you need to add

brokers

code Sample

toKafka="kafka://localhost:9092?topic=test&brokers=localhost:9092";

I hope this will helpful who following the tutorial.

Answer 2

You need to configure the brokers option on the endpoint. Or globally on the kafka component.

I have logged a ticket to make Camel report a better exception in next releases: https://issues.apache.org/jira/browse/CAMEL-12090

There is a Kafka example here you can look at too: https://github.com/apache/camel/tree/master/examples/camel-example-kafka

Answer 3

Probably you've not set producer properties which has configurations provided for Kafka producer.

Kafka component for camel needs to be configured with mandatory Kafka producer properties.

Answer 4

Make sure that the directory C:\\inbox actually exists. Also, make sure that you change the versions of the dependencies in the pom file to the ones mentioned in the tutorial, as things have changed since camel-kafka 2.17.0 , and it no longer accepts zookeeperHost and zookeeperPort values as in the toKafka string.