如何将 bean 注入 Spring Condition 类？

我正在定义条件，稍后我将检查这些条件以动态加载我的服务接口的两个实现之一。

@Component
public class IsPolicyEnabled implements Condition {

    @Autowired
    private MyProperties props;

    @Override
    public boolean matches(ConditionContext arg0, AnnotatedTypeMetadata arg1) {
        return props.isPolicyEnabled();
    }

}

And

@Component
public class MyProperties {...}

And

@Service
@Conditional(IsPolicyEnabled.class)
public class ServiceA implements Service {...}

但是，我遇到了运行时错误。

java.lang.IllegalStateException: Failed to load ApplicationContext
Caused by: java.lang.NullPointerException
at com.xyz.utils.IsPolicyEnabled.matches(IsPolicyEnabled.java:9)
at org.springframework.context.annotation.ConditionEvaluator.shouldSkip(ConditionEvaluator.java:108)
at org.springframework.context.annotation.ConditionEvaluator.shouldSkip(ConditionEvaluator.java:88)
at org.springframework.context.annotation.ConditionEvaluator.shouldSkip(ConditionEvaluator.java:71)
at org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider.isConditionMatch(ClassPathScanningCandidateComponentProvider.java:515)

基本上，它无法初始化在条件实现中自动连接的 props 对象。这是不允许的吗？

由于我的条件评估取决于该依赖项提供的值，因此如何在条件实现中自动连接另一个依赖项？

条件已检查就在之前bean 定义将被注册 [...]

^{Condition, Spring Framework 5.0.8.RELEASE API documentation https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/annotation/Condition.html}

You can't inject a bean into a Condition instance because there are no bean-definitions in the context yet¹.

此外，你不应该在以下范围内使用beanCondition课程：

条件必须遵循与以下相同的限制BeanFactoryPostProcessor and 注意不要与 bean 实例交互.

^{Condition, Spring Framework 5.0.8.RELEASE API documentation https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/annotation/Condition.html}

你应该重新考虑设计，因为

[...]我的状况评估取决于该依赖性提供的值。

表明它不太正确。

^{1 Precisely speaking, there are a few beans already registered by Spring for its own needs.}