@Service
public class MyService {
    public void doSomething() {
        // ...
        doSomethingElse();
    }

    @Transactional
    public void doSomethingElse() {
        // ...
    }
}

@Component
public class MyBean {
    @Autowired
    private MyBean self;

    public void doSomething() {
        // use self reference here
    }
}

@Component
public class MyBean {
    @Autowired
    private MyBean self;

    public void doSomething() {
        // use self reference here
    }
}

@Component
public class MyBean implements ApplicationContextAware {
    private ApplicationContext context;

    @Override
    public void setApplicationContext(ApplicationContext context) throws BeansException {
        this.context = context;
    }

    public void doSomething() {
        MyBean self = context.getBean(MyBean.class);
        // ...
    }
}

/**
	 * Determine whether the given beanName/candidateName pair indicates a self reference,
	 * i.e. whether the candidate points back to the original bean or to a factory method
	 * on the original bean.
	 */
	private boolean isSelfReference(@Nullable String beanName, @Nullable String candidateName) {
		return (beanName != null && candidateName != null &&
				(beanName.equals(candidateName) || (containsBeanDefinition(candidateName) &&
						beanName.equals(getMergedLocalBeanDefinition(candidateName).getFactoryBeanName()))));
	}

/**
	 * Find bean instances that match the required type.
	 * Called during autowiring for the specified bean.
	 * @param beanName the name of the bean that is about to be wired
	 * @param requiredType the actual type of bean to look for
	 * (may be an array component type or collection element type)
	 * @param descriptor the descriptor of the dependency to resolve
	 * @return a Map of candidate names and candidate instances that match
	 * the required type (never {@code null})
	 * @throws BeansException in case of errors
	 * @see #autowireByType
	 * @see #autowireConstructor
	 */
	protected Map<String, Object> findAutowireCandidates(
			@Nullable String beanName, Class<?> requiredType, DependencyDescriptor descriptor) {

		String[] candidateNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
				this, requiredType, true, descriptor.isEager());
		Map<String, Object> result = CollectionUtils.newLinkedHashMap(candidateNames.length);
		for (Map.Entry<Class<?>, Object> classObjectEntry : this.resolvableDependencies.entrySet()) {
			Class<?> autowiringType = classObjectEntry.getKey();
			if (autowiringType.isAssignableFrom(requiredType)) {
				Object autowiringValue = classObjectEntry.getValue();
				autowiringValue = AutowireUtils.resolveAutowiringValue(autowiringValue, requiredType);
				if (requiredType.isInstance(autowiringValue)) {
					result.put(ObjectUtils.identityToString(autowiringValue), autowiringValue);
					break;
				}
			}
		}
		for (String candidate : candidateNames) {
			if (!**isSelfReference**(beanName, candidate) && isAutowireCandidate(candidate, descriptor)) {
				addCandidateEntry(result, candidate, descriptor, requiredType);
			}
		}
		if (result.isEmpty()) {
			boolean multiple = indicatesMultipleBeans(requiredType);
			// Consider fallback matches if the first pass failed to find anything...
			DependencyDescriptor fallbackDescriptor = descriptor.forFallbackMatch();
			for (String candidate : candidateNames) {
				if (!**isSelfReference**(beanName, candidate) && isAutowireCandidate(candidate, fallbackDescriptor) &&
						(!multiple || getAutowireCandidateResolver().hasQualifier(descriptor))) {
					addCandidateEntry(result, candidate, descriptor, requiredType);
				}
			}
			if (result.isEmpty() && !multiple) {
				// Consider self references as a final pass...
				// but in the case of a dependency collection, not the very same bean itself.
				for (String candidate : candidateNames) {
					if (**isSelfReference**(beanName, candidate) &&
							(!(descriptor instanceof MultiElementDescriptor) || !beanName.equals(candidate)) &&
							isAutowireCandidate(candidate, fallbackDescriptor)) {
						addCandidateEntry(result, candidate, descriptor, requiredType);
					}
				}
			}
		}
		return result;
	}

@Component
public class BeanA {
    @Autowired
    private BeanB b;
    @Autowired
    private BeanA a;

}

@Component
public class BeanB {
}

@Component
public class BeanC implements ApplicationContextAware {
    private ApplicationContext context;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.context = context;
    }

    public void doSomething() {
        BeanC self = context.getBean(BeanC.class);
    }
}

Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private org.example.BeanA org.example.BeanA.a; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.example.BeanA] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:573) ~[spring-beans-4.2.8.RELEASE.jar:4.2.8.RELEASE]
	at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.2.8.RELEASE.jar:4.2.8.RELEASE]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331) ~[spring-beans-4.2.8.RELEASE.jar:4.2.8.RELEASE]
	... 16 common frames omitted
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.example.BeanA] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1380) ~[spring-beans-4.2.8.RELEASE.jar:4.2.8.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1126) ~[spring-beans-4.2.8.RELEASE.jar:4.2.8.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1021) ~[spring-beans-4.2.8.RELEASE.jar:4.2.8.RELEASE]
	at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:545) ~[spring-beans-4.2.8.RELEASE.jar:4.2.8.RELEASE]
	... 18 common frames omitted