Spring源码解析 - FactoryBean&&BeanFactory（中）

  @SuppressWarnings("unchecked")
  @Nullable
  private <T> NamedBeanHolder<T> resolveNamedBean(
      ResolvableType requiredType, @Nullable Object[] args, boolean nonUniqueAsNull) throws BeansException {
    Assert.notNull(requiredType, "Required type must not be null");
    String[] candidateNames = getBeanNamesForType(requiredType);
    if (candidateNames.length > 1) {
      List<String> autowireCandidates = new ArrayList<>(candidateNames.length);
      for (String beanName : candidateNames) {
        if (!containsBeanDefinition(beanName) || getBeanDefinition(beanName).isAutowireCandidate()) {
          autowireCandidates.add(beanName);
        }
      }
      if (!autowireCandidates.isEmpty()) {
        candidateNames = StringUtils.toStringArray(autowireCandidates);
      }
    }
    if (candidateNames.length == 1) {
      String beanName = candidateNames[0];
      return new NamedBeanHolder<>(beanName, (T) getBean(beanName, requiredType.toClass(), args));
    }
    else if (candidateNames.length > 1) {
      Map<String, Object> candidates = new LinkedHashMap<>(candidateNames.length);
      for (String beanName : candidateNames) {
        if (containsSingleton(beanName) && args == null) {
          Object beanInstance = getBean(beanName);
          candidates.put(beanName, (beanInstance instanceof NullBean ? null : beanInstance));
        }
        else {
          candidates.put(beanName, getType(beanName));
        }
      }
      String candidateName = determinePrimaryCandidate(candidates, requiredType.toClass());
      if (candidateName == null) {
        candidateName = determineHighestPriorityCandidate(candidates, requiredType.toClass());
      }
      if (candidateName != null) {
        Object beanInstance = candidates.get(candidateName);
        if (beanInstance == null || beanInstance instanceof Class) {
          beanInstance = getBean(candidateName, requiredType.toClass(), args);
        }
        return new NamedBeanHolder<>(candidateName, (T) beanInstance);
      }
      if (!nonUniqueAsNull) {
        throw new NoUniqueBeanDefinitionException(requiredType, candidates.keySet());
      }
    }
    return null;
  }

  @SuppressWarnings("unchecked")
  @Nullable
  private <T> NamedBeanHolder<T> resolveNamedBean(
      ResolvableType requiredType, @Nullable Object[] args, boolean nonUniqueAsNull) throws BeansException {
    Assert.notNull(requiredType, "Required type must not be null");
    // 该方法根据传入的Class类型获取BeanName，因为有接口有多个实现类情况，所以这里返回是String数组。
    // 调用getBean方法传入的type为com.javaedge.FactoryBeanService类型，但没有在Spring容器中注入FactoryBeanService类型的Bean
    // 所以讲道理在这里应该获取不到beanName，事实是这样吗？看对getBeanNamesForType的分析
    String[] candidateNames = getBeanNamesForType(requiredType);
    // 有多个BeanName，则挑最合适的
    if (candidateNames.length > 1) {
      List<String> autowireCandidates = new ArrayList<>(candidateNames.length);
      for (String beanName : candidateNames) {
        if (!containsBeanDefinition(beanName) || getBeanDefinition(beanName).isAutowireCandidate()) {
          autowireCandidates.add(beanName);
        }
      }
      if (!autowireCandidates.isEmpty()) {
        candidateNames = StringUtils.toStringArray(autowireCandidates);
      }
    }
    // 如果只有一个BeanName，调用getBean获取Bean实例放到NamedBeanHolder
    // todo
    if (candidateNames.length == 1) {
      String beanName = candidateNames[0];
      return new NamedBeanHolder<>(beanName, (T) getBean(beanName, requiredType.toClass(), args));
    }
    // 经过挑选后，如果合适的BeanName还是多个
    else if (candidateNames.length > 1) {
      Map<String, Object> candidates = new LinkedHashMap<>(candidateNames.length);
      for (String beanName : candidateNames) {
        // 看看是不是已经创建过的单例Bean
        if (containsSingleton(beanName) && args == null) {
          Object beanInstance = getBean(beanName);
          candidates.put(beanName, (beanInstance instanceof NullBean ? null : beanInstance));
        }
        else {
          // 调用getType继续获取Bean实例
          candidates.put(beanName, getType(beanName));
        }
      }
      // 有多个Bean实例，则取带有Primary注解或者带有Primary信息的
      String candidateName = determinePrimaryCandidate(candidates, requiredType.toClass());
      if (candidateName == null) {
        // 如果没有Primary注解或者Primary相关的信息，则取优先级高的Bean
        candidateName = determineHighestPriorityCandidate(candidates, requiredType.toClass());
      }
      if (candidateName != null) {
        Object beanInstance = candidates.get(candidateName);
        // Class类型的话 继续调用getBean获取Bean实例
        if (beanInstance == null || beanInstance instanceof Class) {
          beanInstance = getBean(candidateName, requiredType.toClass(), args);
        }
        return new NamedBeanHolder<>(candidateName, (T) beanInstance);
      }
      if (!nonUniqueAsNull) {
        // 都没获取到，抛出异常
        throw new NoUniqueBeanDefinitionException(requiredType, candidates.keySet());
      }
    }
    return null;
  }