java - 通过工厂方法实例化 Bean 失败；异常 org.springframework.beans.BeanInstantiationException

Question

我有以下 Kafka 的 Spring 配置:

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());
  }    
}

我将项目迁移到最新的 Spring cloud 2021.0.1 和 Spring Boot 2.6.6。但是我在启动时收到以下错误堆栈:

    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

你知道我该如何解决这个问题吗？

Answer 1

错误堆栈跟踪表明在 producerFactory() 方法中创建 DefaultKafkaProducerFactory 的新实例时发生了 NullPointerException .

在内部，DefaultKafkaProducerFactory creates a ConcurrentHashMap使用提供的信息来维护其配置。

正如您在 ConcurrentHashMap javadocs 中看到的那样，如果提供的任何键或值是 null，put 方法将引发 NullPointerException。

因此，keySerializer、valueSerializer 或 bootstrapServers 中的一个或多个变量可能为空。

我假设这些值是根据您的 @ConfigurationProperties kafka.status.producer 通过依赖注入(inject)填充的。请确保在您的 Spring 配置中正确定义了这些属性。

出于测试目的，请尝试删除 @RefreshScope 注释:它可能是问题的原因。

反之亦然。如 Spring Cloud 文档中所示 talking about @RefreshScope :

@RefreshScope works (technically) on a @Configuration class,but it might lead to surprising behavior. For example, it does notmean that all the @Beans defined in that class are themselves in@RefreshScope. Specifically, anything that depends on those beanscannot rely on them being updated when a refresh is initiated, unlessit is itself in @RefreshScope. In that case, it is rebuilt on arefresh and its dependencies are re-injected. At that point, they arere-initialized from the refreshed @Configuration).

从这个角度来看，如果用 @RefreshScope 注释 producerFactory bean 也是完全合理的。我会尝试:

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());
  }    
}

请注意包含额外的 @RefreshScope 注释。

最后，考虑查看 Spring Kafka 项目文档，它提供了几个有关如何配置项目的示例，无论您是否使用 Spring Boot或 not ，并为您提供有关 DefaultKafkaProducerFactory 的更多背景信息.

正如您在上述文档中所见，如果您使用的是 Spring Boot，就像您的情况一样，代码可以大大简化。考虑查看 Spring Boot related documentation关于主题和related properties configuration .