getBean（“aBService”）

getBean（ABService.class）

applicationContext.getBeansOfType(ABService.class).forEach((beanName,bean)->{
            System.out.println(beanName + ":" + bean);
        });

org.springframework.context.annotation.AnnotationBeanNameGenerator#generateBeanName

org.springframework.context.annotation.AnnotationBeanNameGenerator

@Override
  public String generateBeanName(BeanDefinition definition, BeanDefinitionRegistry registry) {
    if (definition instanceof AnnotatedBeanDefinition) {
      String beanName = determineBeanNameFromAnnotation((AnnotatedBeanDefinition) definition);
      if (StringUtils.hasText(beanName)) {
        // Explicit bean name found.
        return beanName;
      }
    }
    // Fallback: generate a unique default bean name.
    return buildDefaultBeanName(definition, registry);
  }

protected String buildDefaultBeanName(BeanDefinition definition) {
    String beanClassName = definition.getBeanClassName();
    Assert.state(beanClassName != null, "No bean class name set");
    String shortClassName = ClassUtils.getShortName(beanClassName);
    return Introspector.decapitalize(shortClassName);
  }

public static String decapitalize(String name) {
        if (name == null || name.length() == 0) {
            return name;
        }
        if (name.length() > 1 && Character.isUpperCase(name.charAt(1)) &&
                        Character.isUpperCase(name.charAt(0))){
            return name;
        }
        char chars[] = name.toCharArray();
        chars[0] = Character.toLowerCase(chars[0]);
        return new String(chars);
    }

/**
     * Utility method to take a string and convert it to normal Java variable
     * name capitalization. This normally means converting the first
     * character from upper case to lower case, but in the (unusual) special
     * case when there is more than one character and both the first and
     * second characters are upper case, we leave it alone.
     * <p>
     * Thus "FooBah" becomes "fooBah" and "X" becomes "x", but "URL" stays
     * as "URL".
     *
     * @param name The string to be decapitalized.
     * @return The decapitalized version of the string.
     */