BeanFactoryAnnotationUtils.java 文件源码

/**
 * Obtain a bean of type {@code T} from the given {@code BeanFactory} declaring a qualifier
 * (e.g. {@code <qualifier>} or {@code @Qualifier}) matching the given qualifier).
 * @param bf the BeanFactory to get the target bean from
 * @param beanType the type of bean to retrieve
 * @param qualifier the qualifier for selecting between multiple bean matches
 * @return the matching bean of type {@code T} (never {@code null})
 * @throws NoSuchBeanDefinitionException if no matching bean of type {@code T} found
 */
private static <T> T qualifiedBeanOfType(ConfigurableListableBeanFactory bf, Class<T> beanType, String qualifier) {
    Map<String, T> candidateBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(bf, beanType);
    T matchingBean = null;
    for (String beanName : candidateBeans.keySet()) {
        if (isQualifierMatch(qualifier, beanName, bf)) {
            if (matchingBean != null) {
                throw new NoSuchBeanDefinitionException(qualifier, "No unique " + beanType.getSimpleName() +
                        " bean found for qualifier '" + qualifier + "'");
            }
            matchingBean = candidateBeans.get(beanName);
        }
    }
    if (matchingBean != null) {
        return matchingBean;
    }
    else if (bf.containsBean(qualifier)) {
        // Fallback: target bean at least found by bean name - probably a manually registered singleton.
        return bf.getBean(qualifier, beanType);
    }
    else {
        throw new NoSuchBeanDefinitionException(qualifier, "No matching " + beanType.getSimpleName() +
                " bean found for qualifier '" + qualifier + "' - neither qualifier match nor bean name match!");
    }
}