techprimers / spring-boot-kafka-producer-example

Spring Boot Kafka Producer Example

Spring Boot with Kafka Producer Example

This Project covers how to use Spring Boot with Spring Kafka to Publish JSON/String message to a Kafka topic

Start Zookeeper

• bin/zookeeper-server-start.sh config/zookeeper.properties

Start Kafka Server

• bin/kafka-server-start.sh config/server.properties

Create Kafka Topic

• bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic Kafka_Example

Consume from the Kafka Topic via Console

• bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic Kafka_Example --from-beginning

Publish message via WebService

• http://localhost:8081/kafka/publish/Sam
• http://localhost:8081/kafka/publish/Peter

spring-boot-kafka-producer-example's Issues

How can i solve this issue?

2021-10-02 13:20:51.829 ERROR 12929 --- [nio-8081-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.apache.kafka.common.errors.SerializationException: Can't convert value of class model.User to class org.apache.kafka.common.serialization.StringSerializer specified in value.serializer] with root cause

java.lang.ClassCastException: class model.User cannot be cast to class java.lang.String (model.User is in unnamed module of loader 'app'; java.lang.String is in module java.base of loader 'bootstrap')
at org.apache.kafka.common.serialization.StringSerializer.serialize(StringSerializer.java:28) ~[kafka-clients-2.7.1.jar:na]
at org.apache.kafka.common.serialization.Serializer.serialize(Serializer.java:62) ~[kafka-clients-2.7.1.jar:na]
at org.apache.kafka.clients.producer.KafkaProducer.doSend(KafkaProducer.java:926) ~[kafka-clients-2.7.1.jar:na]
at org.apache.kafka.clients.producer.KafkaProducer.send(KafkaProducer.java:886) ~[kafka-clients-2.7.1.jar:na]
at org.springframework.kafka.core.DefaultKafkaProducerFactory$CloseSafeProducer.send(DefaultKafkaProducerFactory.java:864) ~[spring-kafka-2.7.7.jar:2.7.7]
at org.springframework.kafka.core.KafkaTemplate.doSend(KafkaTemplate.java:580) ~[spring-kafka-2.7.7.jar:2.7.7]
at org.springframework.kafka.core.KafkaTemplate.send(KafkaTemplate.java:380) ~[spring-kafka-2.7.7.jar:2.7.7]
at com.test.kafka.springbootkafkaproducerexample.resource.UserResource.post(UserResource.java:23) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:567) ~[na:na]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-5.3.10.jar:5.3.10]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-5.3.10.jar:5.3.10]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.10.jar:5.3.10]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.10.jar:5.3.10]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.10.jar:5.3.10]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.10.jar:5.3.10]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1067) ~[spring-webmvc-5.3.10.jar:5.3.10]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.10.jar:5.3.10]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.10.jar:5.3.10]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.10.jar:5.3.10]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:655) ~[tomcat-embed-core-9.0.53.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.10.jar:5.3.10]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) ~[tomcat-embed-core-9.0.53.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.53.jar:9.0.53]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.10.jar:5.3.10]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.10.jar:5.3.10]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.10.jar:5.3.10]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.10.jar:5.3.10]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.10.jar:5.3.10]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.10.jar:5.3.10]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:197) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:540) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:135) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1726) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.53.jar:9.0.53]
at java.base/java.lang.Thread.run(Thread.java:831) ~[na:na]