BeanNameGenerator如何改变beanName的生成策略、如何自己写一个beanName的生成策略

Spring中Bean名的自定义生成策略

1. AnnotationBeanNameGenerator

 /**
     * 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.
     * 

     * 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.
     */
    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);
    }

正常情况下将首字母变成消息，当第一第二个字母都是大写时，不做任何改变。

2. DefaultBeanGenerator

    /**
     * Generate a bean name for the given bean definition, unique within the
     * given bean factory.
     * @param definition the bean definition to generate a bean name for
     * @param registry the bean factory that the definition is going to be
     * registered with (to check for existing bean names)
     * @param isInnerBean whether the given bean definition will be registered
     * as inner bean or as top-level bean (allowing for special name generation
     * for inner beans versus top-level beans)
     * @return the generated bean name
     * @throws BeanDefinitionStoreException if no unique name can be generated
     * for the given bean definition
     */
    public static String generateBeanName(
            BeanDefinition definition, BeanDefinitionRegistry registry, boolean isInnerBean)
            throws BeanDefinitionStoreException {

        String generatedBeanName = definition.getBeanClassName();
        if (generatedBeanName == null) {
            if (definition.getParentName() != null) {
                // parent$child
                generatedBeanName = definition.getParentName() + "$child";
            }
            else if (definition.getFactoryBeanName() != null) {
                // factoryName$create
                generatedBeanName = definition.getFactoryBeanName() + "$created";
            }
        }
        // 如果字符串里面的值为null， ""， "   "，那么返回值为false；否则为true
        if (!StringUtils.hasText(generatedBeanName)) {
            throw new BeanDefinitionStoreException("Unnamed bean definition specifies neither " +
                    "'class' nor 'parent' nor 'factory-bean' - can't generate bean name");
        }

        String id = generatedBeanName;
        if (isInnerBean) {
            // 内部类 
            // Inner bean: generate identity hashcode suffix.
            id = generatedBeanName + GENERATED_BEAN_NAME_SEPARATOR + ObjectUtils.getIdentityHexString(definition);
        }
        else {
            // Top-level bean: use plain class name with unique suffix if necessary.
            return uniqueBeanName(generatedBeanName, registry);
        }
        return id;
    }

当bean 是顶级类的时候的生成策略

    /**
     * Turn the given bean name into a unique bean name for the given bean factory,
     * appending a unique counter as suffix if necessary.
     * @param beanName the original bean name
     * @param registry the bean factory that the definition is going to be
     * registered with (to check for existing bean names)
     * @return the unique bean name to use
     * @since 5.1
     */
    public static String uniqueBeanName(String beanName, BeanDefinitionRegistry registry) {
        String id = beanName;
        int counter = -1;

        // Increase counter until the id is unique.
        // 不停+1 重试是否已经有名称，知到生成成功
        while (counter == -1 || registry.containsBeanDefinition(id)) {
            counter++;
            id = beanName + GENERATED_BEAN_NAME_SEPARATOR + counter;
        }
        return id;
    }