spring注解@Component、@Service等自动生成bean的命名规则

参考链接：信息来源

今天碰到一个问题，写了一个@Service的bean，类名大致为：CUser

xml配置：

<context:component-scan base-package="com.xxx.xx.x"/>

结果启动报错：No bean named 'cUser' is defined，即找不到名为cUser的bean

bean的名字不是我预期的"cUser"，临时将bean的名字硬性指定成了cUser来解决的，即：@Service("cUser")

 在网上找了半天，看到有位兄弟说得很有道理，引用一下（以下内容引用自篇首链接）：

    但还是觉得比较奇怪，之前一直以为Spring对注解形式的bean的名字的默认处理就是将首字母小写，再拼接后面的字符，但今天看来不是这样的。

回来翻了一下原码，原来还有另外的一个特殊处理：当类的名字是以两个或以上的大写字母开头的话，bean的名字会与类名保持一致

 

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/**
     * Derive a default bean name from the given bean definition.
     * <p>The default implementation simply builds a decapitalized version
     * of the short class name: e.g. "mypackage.MyJdbcDao" -> "myJdbcDao".
     * <p>Note that inner classes will thus have names of the form
     * "outerClassName.InnerClassName", which because of the period in the
     * name may be an issue if you are autowiring by name.
     * @param definition the bean definition to build a bean name for
     * @return the default bean name (never {@code null})
     */
    protected String buildDefaultBeanName(BeanDefinition definition) {
        String shortClassName = ClassUtils.getShortName(definition.getBeanClassName());
        return Introspector.decapitalize(shortClassName);
    }

 

    /**
     * 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.
     */
    public static String decapitalize(String name) {
        if (name == null || name.length() == 0) {
            return name;
        }
　　　　// 如果发现类的前两个字符都是大写，则直接返回类名
        if (name.length() > 1 && Character.isUpperCase(name.charAt(1)) &&
                        Character.isUpperCase(name.charAt(0))){
            return name;
        }
　　　　// 将类名的第一个字母转成小写，然后返回
        char chars[] = name.toCharArray();
        chars[0] = Character.toLowerCase(chars[0]);
        return new String(chars);
    }