英文:
Why @autowired is not required?
问题
为什么对于后续的方法，我不需要要求使用 @Autowired 来注入 consumerFactory？而当我这样做时，会收到循环依赖的异常。
我是否漏掉了一些基本的东西，我猜是的。
感谢帮助。
@Bean
public ConsumerFactory<String, String> consumerFactory() {
return new DefaultKafkaConsumerFactory<>(consumerConfig());
}
@Bean
public KafkaListenerContainerFactory<
ConcurrentMessageListenerContainer<String, String>> factory(
ConsumerFactory<String, String> consumerFactory
) {
ConcurrentKafkaListenerContainerFactory<String, String> factory =
new ConcurrentKafkaListenerContainerFactory<>();
factory.setConsumerFactory(consumerFactory);
return factory;
}
英文:
why for a later method I do not need to require @Autowired to inject consumerFactory? And when I do so I receive a circular dependency exception.
Am I missing something fundamental, I guess yes.
Thanks for the help.
@Bean
public ConsumerFactory<String, String> consumerFactory() {
return new DefaultKafkaConsumerFactory<>(consumerConfig());
}
@Bean
public KafkaListenerContainerFactory<
ConcurrentMessageListenerContainer<String, String>> factory(
ConsumerFactory<String, String> consumerFactory
) {
ConcurrentKafkaListenerContainerFactory<String, String> factory =
new ConcurrentKafkaListenerContainerFactory<>();
factory.setConsumerFactory(consumerFactory);
return factory;
}
答案1
得分: 1
Spring会自动检测带有@Bean注解的factory()方法需要一个ConsumerFactory来创建KafkaListenerContainerFactory的实例。因此，它已经知道需要为此提供一个依赖项。
只有在你的类需要一个依赖项时才需要使用@Autowired，例如：
@Component
public class SomeClass {
@Autowired
private ConsumerFactory<String, String> consumerFactory;
}
另一种方法是将其定义为构造函数参数，然后不需要@Autowired，因为构造函数签名已经清楚：
@Component
public class SomeClass {
private ConsumerFactory<String, String> consumerFactory;
public SomeClass(ConsumerFactory<String, String> consumerFactory) {
this.consumerFactory = consumerFactory;
}
}
英文:
Spring automatically detects that the @Bean annotated method factory() requires a ConsumerFactory to create an instance of KafkaListenerContainerFactory. Hence it already knows that it needs to provide a dependency for that.
@Autowired is only required if you have a class that requires a dependency, for example:
@Component
public class SomeClass {
@Autowired
private ConsumerFactory<String, String> consumerFactory;
}
An alternative to this would be to define this as constructor argument, then you don't need @Autowired as well as it's already clear thanks to the constructor signature:
@Component
public class SomeClass {
private ConsumerFactory<String, String> consumerFactory;
public SomeClass(ConsumerFactory<String, String> consumerFactory) {
this.consumerFactory = consumerFactory;
}
}
答案2
得分: 1
你在同一类中使用了一个方法来初始化ConsumerFactory对象（我怀疑它是一个带有**@Configuration**注解的配置类）。
@Bean注解创建了另一个元素并将其添加到Spring引擎维护的集合中。
英文:
You use a method defined in the same class to initialize the ConsumerFactory object (I suspect it's a configuration class annotated with @Configuration).
The @Bean annotation creates another element and adds it to the set maintained by Spring engine.
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