Spring 注释 conditionalOnBean 不起作用 [英] Spring annotation conditionalOnBean not working

问题描述

我定义了一个带有注解配置的类

I defined a class with annotation Configuration

    @Configuration
    @AutoConfigureAfter(EndpointAutoConfiguration.class)
    public class EndpointConfiguration {
        @Resource
        private MetricsEndpoint metricsEndpoint;

        @Bean
        public MetricsFormatEndpoint metricsFormatEndpoint() {
            return new MetricsFormatEndpoint(metricsEndpoint);
        }
    }

MetricsFormatEndpoint 运行良好.

the MetricsFormatEndpoint works well.

但是我使用了注解conditionalOnBean，它根本不起作用.

but I use the annotation conditionalOnBean, it doesn't work at all.

    @Bean
    @ConditionalOnBean(MetricsEndpoint.class)
    public MetricsFormatEndpoint metricsFormatEndpoint() {
        return new MetricsFormatEndpoint(metricsEndpoint);
    }

查看 localhost:8080/beans，spring applicationContext 有 bean 'metricsEndpoint'，

see the localhost:8080/beans,the spring applicationContext has the bean 'metricsEndpoint',

    {"bean":"metricsEndpoint","scope":"singleton",
     "type":"org.springframework.boot.actuate.endpoint.MetricsEndpoint",
     "resource":"class path resource 
    [org/springframework/boot/actuate/autoconfigure/EndpointAutoConfiguration.class]",
    "dependencies":[]}

我看了注解@ConditionalOnBean 的文档，它说应该检查的bean 的类类型.当 {@link ApplicationContext} 中包含任何指定的类时，条件匹配.

I read the document of the annotation @ConditionalOnBean, it says The class type of bean that should be checked. The condition matches when any of the classes specified is contained in the {@link ApplicationContext}.

谁能告诉我为什么

推荐答案

@ConditionalOnBean 的 javadoc 将其描述为:

The javadoc for @ConditionalOnBean describes it as:

Conditional 仅当指定的 bean 类和/或名称已包含在 BeanFactory 中时才匹配.

Conditional that only matches when the specified bean classes and/or names are already contained in the BeanFactory.

在这种情况下，关键部分是已经包含在 BeanFactory 中".在任何自动配置类之前考虑您自己的配置类.这意味着 MetricsEndpoint bean 的自动配置尚未在您自己的配置检查其存在时发生，因此，您的 MetricsFormatEndpoint bean未创建.

In this case, the key part is "already contained in the BeanFactory". Your own configuration classes are considered before any auto-configuration classes. This means that the auto-configuration of the MetricsEndpoint bean hasn't happened by the time that your own configuration is checking for its existence and, as a result, your MetricsFormatEndpoint bean isn't created.

一种方法是 为您的 MetricsFormatEndpoint bean 创建您自己的自动配置类，并使用 @AutoConfigureAfter(EndpointAutoConfiguration.class) 对其进行注释.这将确保在定义 MetricsEndpoint bean 之后评估其条件.

One approach to take would be to create your own auto-configuration class for your MetricsFormatEndpoint bean and annotate it with @AutoConfigureAfter(EndpointAutoConfiguration.class). That will ensure that its conditions are evaluated after the MetricsEndpoint bean has been defined.

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