Description
When registering two singleton beans using org.springframework.beans.factory.config.SingletonBeanRegistry#registerSingleton, and use @ConditionalOnSingleCandidate(TestBean.class) a NullPointerException occurs due to the absence of corresponding bean definitions.
Reproduction Steps
Register singleton bean using SingletonBeanRegistry#registerSingleton:
```java
beanFactory.registerSingleton("bean1", new TestBean());
beanFactory.registerSingleton("bean2", new TestBean());
use @ConditionalOnSingleCandidate(TestBean.class)
```java
@Configuration
@ConditionalOnSingleCandidate(TestBean.class)
public class TestConfiguration {
@Bean
public SomeBean someBean() {
return new SomeBean();
}
}
The application will throw a NullPointerException during startup.
Environment Information Spring Boot Version: 3.5.7 JDK Version: 21
Comment From: linw-bai
The method org.springframework.boot.autoconfigure.condition.OnBeanCondition#getMatchingBeans does not account for cases where there is no BeanDefinition.
Caused by: java.lang.NullPointerException: null
at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchingBeans(OnBeanCondition.java:474) ~[spring-boot-autoconfigure-3.5.7.jar:3.5.7]
at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getPrimaryBeans(OnBeanCondition.java:464) ~[spring-boot-autoconfigure-3.5.7.jar:3.5.7]
at org.springframework.boot.autoconfigure.condition.OnBeanCondition.evaluateConditionalOnSingleCandidate(OnBeanCondition.java:176) ~[spring-boot-autoconfigure-3.5.7.jar:3.5.7]
at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchOutcome(OnBeanCondition.java:136) ~[spring-boot-autoconfigure-3.5.7.jar:3.5.7]
at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:47) ~[spring-boot-autoconfigure-3.5.7.jar:3.5.7]
... 17 common frames omitted