Bean instantiation via factory method failed; exception org.springframework.beans.BeanInstantiationException

Question

I have the following Spring configuration for Kafka:

import org.apache.kafka.clients.producer.ProducerConfig;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.kafka.core.DefaultKafkaProducerFactory;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.kafka.core.ProducerFactory;

import java.util.HashMap;
import java.util.Map;

@Configuration
@RefreshScope
@ConfigurationProperties(prefix = "kafka.status.producer")
public class StatusKafkaProducerConfig {

  private String keySerializer;
  private String valueSerializer;
  private String bootstrapServers;

  public void setKeySerializer(String keySerializer) {
    this.keySerializer = keySerializer;
  }

  public void setValueSerializer(String valueSerializer) {
    this.valueSerializer = valueSerializer;
  }

  public void setBootstrapServers(String bootstrapServers) {
    this.bootstrapServers = bootstrapServers;
  }

  @Bean
  public Map<String, Object> producerConfigs() {
    Map<String, Object> properties = new HashMap<>();

    properties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, keySerializer);
    properties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, valueSerializer);
    properties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);

    return properties;
  }

  @Bean
  @RefreshScope
  public KafkaTemplate<String, String> kafkaTemplate() {
    return new KafkaTemplate<>(producerFactory());
  }

  @Bean
  public ProducerFactory<String, String> producerFactory() {
    return new DefaultKafkaProducerFactory<>(producerConfigs());
  }    
}

I migrated the project to latest Spring cloud 2021.0.1 and Spring Boot 2.6.6. But I get the following error stack during boot time:

    2022-04-30 19:14:08.350 ERROR 23684 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'producerFactory' defined in class path resource [com/test/StatusUpdateKafkaProducerConfig.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.kafka.core.ProducerFactory]: Factory method 'producerFactory' threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:658) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:486) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1352) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1195) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:582) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:953) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918) ~[spring-context-5.3.19.jar:5.3.19]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583) ~[spring-context-5.3.19.jar:5.3.19]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) ~[spring-boot-2.6.7.jar:2.6.7]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:740) ~[spring-boot-2.6.7.jar:2.6.7]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:415) ~[spring-boot-2.6.7.jar:2.6.7]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) ~[spring-boot-2.6.7.jar:2.6.7]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1312) ~[spring-boot-2.6.7.jar:2.6.7]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301) ~[spring-boot-2.6.7.jar:2.6.7]
    at com.test.Application.main(Application.java:82) ~[main/:na]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.kafka.core.ProducerFactory]: Factory method 'producerFactory' threw exception; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.3.19.jar:5.3.19]
    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:653) ~[spring-beans-5.3.19.jar:5.3.19]
    ... 19 common frames omitted
Caused by: java.lang.NullPointerException: null
    at java.base/java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011) ~[na:na]
    at java.base/java.util.concurrent.ConcurrentHashMap.putAll(ConcurrentHashMap.java:1089) ~[na:na]
    at java.base/java.util.concurrent.ConcurrentHashMap.<init>(ConcurrentHashMap.java:852) ~[na:na]
    at org.springframework.kafka.core.DefaultKafkaProducerFactory.<init>(DefaultKafkaProducerFactory.java:205) ~[spring-kafka-2.8.5.jar:2.8.5]
    at org.springframework.kafka.core.DefaultKafkaProducerFactory.<init>(DefaultKafkaProducerFactory.java:168) ~[spring-kafka-2.8.5.jar:2.8.5]
    at com.test.StatusUpdateKafkaProducerConfig.producerFactory(TransactionStatusUpdateKafkaProducerConfig.java:53) ~[commons-0.0.1-plain.jar:na]
    at com.test.StatusUpdateKafkaProducerConfig$$EnhancerBySpringCGLIB$$e907de88.CGLIB$producerFactory$0(<generated>) ~[commons-0.0.1-plain.jar:na]
    at com.test.StatusUpdateKafkaProducerConfig$$EnhancerBySpringCGLIB$$e907de88$$FastClassBySpringCGLIB$$db10662a.invoke(<generated>) ~[commons-0.0.1-plain.jar:na]
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244) ~[spring-core-5.3.19.jar:5.3.19]
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:331) ~[spring-context-5.3.19.jar:5.3.19]
    at com.StatusUpdateKafkaProducerConfig$$EnhancerBySpringCGLIB$$e907de88.producerFactory(<generated>) ~[commons-0.0.1-plain.jar:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[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:568) ~[na:na]
    at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:282) ~[spring-core-5.3.19.jar:5.3.19]
    at org.springframework.cloud.context.scope.GenericScope$LockedScopedProxyFactoryBean.invoke(GenericScope.java:485) ~[spring-cloud-context-3.1.2.jar:3.1.2]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.19.jar:5.3.19]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:763) ~[spring-aop-5.3.19.jar:5.3.19]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:708) ~[spring-aop-5.3.19.jar:5.3.19]
    at com.StatusUpdateKafkaProducerConfig$$EnhancerBySpringCGLIB$$6800bd04.producerFactory(<generated>) ~[commons-0.0.1-plain.jar:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[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:568) ~[na:na]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.3.19.jar:5.3.19]
    ... 20 common frames omitted

Do you know how I can fix this issue?

Answer 1

The error stack trace is indicating that a NullPointerException is happening when you are creating a new instance of DefaultKafkaProducerFactory in the producerFactory() method.

Internally, DefaultKafkaProducerFactory creates a ConcurrentHashMap with the provided information to maintain its configuration.

As you can see in the ConcurrentHashMap javadocs, the put method will raise NullPointerException if any of the provided keys or values are null.

As a consequence, probably one of or several of the variables keySerializer, valueSerializer or bootstrapServers are null.

I assume these values are filled by dependency injection according to your @ConfigurationProperties kafka.status.producer. Please, be sure these properties are correctly defined in your Spring configuration.

For testing purposes, try removing the @RefreshScope annotation: it may be a cause of the problem.

The contrary can be a valid solution as well. As indicated in the Spring Cloud documentation when talking about @RefreshScope:

@RefreshScope works (technically) on a @Configuration class, but it might lead to surprising behavior. For example, it does not mean that all the @Beans defined in that class are themselves in @RefreshScope. Specifically, anything that depends on those beans cannot rely on them being updated when a refresh is initiated, unless it is itself in @RefreshScope. In that case, it is rebuilt on a refresh and its dependencies are re-injected. At that point, they are re-initialized from the refreshed @Configuration).

From that point of view if make perfect sense to annotate with @RefreshScope the producerFactory bean as well. I would try:

import org.apache.kafka.clients.producer.ProducerConfig;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.cloud.context.config.annotation.RefreshScope;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.kafka.core.DefaultKafkaProducerFactory;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.kafka.core.ProducerFactory;

import java.util.HashMap;
import java.util.Map;

@Configuration
@RefreshScope
@ConfigurationProperties(prefix = "kafka.status.producer")
public class StatusKafkaProducerConfig {

  private String keySerializer;
  private String valueSerializer;
  private String bootstrapServers;

  public void setKeySerializer(String keySerializer) {
    this.keySerializer = keySerializer;
  }

  public void setValueSerializer(String valueSerializer) {
    this.valueSerializer = valueSerializer;
  }

  public void setBootstrapServers(String bootstrapServers) {
    this.bootstrapServers = bootstrapServers;
  }

  @Bean
  @RefreshScope
  public Map<String, Object> producerConfigs() {
    Map<String, Object> properties = new HashMap<>();

    properties.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, keySerializer);
    properties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, valueSerializer);
    properties.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);

    return properties;
  }

  @Bean
  @RefreshScope
  public KafkaTemplate<String, String> kafkaTemplate() {
    return new KafkaTemplate<>(producerFactory());
  }

  @Bean
  @RefreshScope
  public ProducerFactory<String, String> producerFactory() {
    return new DefaultKafkaProducerFactory<>(producerConfigs());
  }    
}

Please, note the inclusion of the additional @RefreshScope annotations.

Finally, consider review the Spring Kafka project documentation, it provides several examples about how to configure your project, whether you are using Spring Boot or not, and gives you further background about DefaultKafkaProducerFactory.

As you can see in the aforementioned docs, if you are using Spring Boot, like in you case, the code can be greatly simplified. Consider review the Spring Boot related documentation about the subject and related properties configuration.