根据属性动态注册Spring Bean

我正在使用最新的 Spring Boot 版本，并尝试根据中定义的内容动态创建 n 个 beanapplication.yaml文件。然后我想根据 bean 名称将这些 bean 注入到其他类中。

下面的代码是我想要实现的目标的一个非常简化的示例。自动配置通常是 spring boot starter 库的一部分，因此需要注册的 bean 数量未知。

@Slf4j
@Value
public class BeanClass {

    private final String name;

    public void logName() {
        log.info("Name: {}", name);
    }

}

@Component
@RequiredArgsConstructor
public class ServiceClass {

    private final BeanClass fooBean;
    private final BeanClass barBean;

    public void log() {
        fooBean.logName();
        barBean.logName();
    }

}

@Value
@ConfigurationProperties
public class BeanProperties {

    private final List<String> beans;

}

@Configuration
public class AutoConfiguration {

    // Obviously not correct
    @Bean
    public List<BeanClass> beans(final BeanProperties beanProperties) {
        return beanProperties.getBeans().stream()
                .map(BeanClass::new)
                .collect(Collectors.toList());
    }

}

@EnableConfigurationProperties(BeanProperties.class)
@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        final ConfigurableApplicationContext context = SpringApplication.run(DemoApplication.class, args);
        final ServiceClass service = context.getBean(ServiceClass.class);
        service.log();
    }

}

beansToMake:
  - fooBean
  - barBean

我在谷歌上尝试了多种建议，但没有任何效果，而且似乎已经过时了。我希望 Spring 的一个新功能能让这一切变得简单。

你可以实施BeanDefinitionRegistryPostProcessor界面 https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/beans/factory/support/BeanDefinitionRegistryPostProcessor.html注册BeanClassbeans的定义如下：

public class DynamicBeanDefinitionRegistrar implements BeanDefinitionRegistryPostProcessor {

  public static final String PROPERTIES_PREFIX = "beans";
  private final List<String> beanNames;

  public DynamicBeanDefinitionRegistrar(Environment environment) {
    beanNames =
        Binder.get(environment)
            .bind(PROPERTIES_PREFIX, Bindable.listOf(String.class))
            .orElseThrow(IllegalStateException::new);
  }

  @Override
  public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)
      throws BeansException {
    beanNames.forEach(
        beanName -> {
          GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
          beanDefinition.setBeanClass(BeanClass.class);
          beanDefinition.setInstanceSupplier(() -> new BeanClass(beanName));
          registry.registerBeanDefinition(beanName, beanDefinition);
        });
  }

  @Override
  public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
      throws BeansException {}
}

由于在实例化bean之前需要属性，因此要注册BeanClass豆类的定义，@ConfigurationProperties不适合这种情况。反而，活页夹API https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.0-Release-Notes#configuration-property-binding用于以编程方式绑定它们。

Because BeanDefinitionPostProcessor对象必须在容器生命周期的早期实例化，@Bean方法应标记为静态@Configuration类，根据Spring文档 https://docs.spring.io/spring-framework/docs/5.0.x/javadoc-api/org/springframework/context/annotation/Bean.html.

@Configuration
public class DynamicBeanDefinitionRegistrarConfiguration {
  @Bean
  public static DynamicBeanDefinitionRegistrar beanDefinitionRegistrar(Environment environment) {
    return new DynamicBeanDefinitionRegistrar(environment);
  }
}

结果，您定义的所有 beanapplication.yml，注册为BeanClass beans:

beans: 
    - fooBean
    - barBean

以供参考：使用 BeanDefinitionRegistryPostProcessor 创建 N 个 Bean https://stackoverflow.com/questions/53462889/create-n-number-of-beans-with-beandefinitionregistrypostprocessor, 从属性文件创建 Spring Boot 动态 Bean https://stackoverflow.com/questions/48161636/spring-boot-dynamic-bean-creation-from-properties-file