AnnotationConfigApplicationContext是把注册交给AnnotatedBeanDefinitionReader的，在AnnotatedBeanDefinitionReader有个属性是beaNameGenerator

private BeanNameGenerator beanNameGenerator = AnnotationBeanNameGenerator.INSTANCE;

BeanNameGenerator此接口有一个方法

String generateBeanName(BeanDefinition definition, BeanDefinitionRegistry registry);

实现此接口的都可以用BeanDefinition和BeanDefinitionRegistry来获取beanName

AnnotationBeanNameGenerator的实现：

	@Overridepublic String generateBeanName(BeanDefinition definition, BeanDefinitionRegistry registry) {if (definition instanceof AnnotatedBeanDefinition) {//判断definition是否是AnnotatedBeanDefinitionString beanName = determineBeanNameFromAnnotation((AnnotatedBeanDefinition) definition);//如果有自定义beanName的返回beanNameif (StringUtils.hasText(beanName)) {//如果beanName有数据就返回// Explicit bean name found.return beanName;}}// Fallback: generate a unique default bean name.return buildDefaultBeanName(definition, registry);//如果没有自定义名称就自动实现名称定义}

先看determineBeanNameFromAnnotation方法

@Nullableprotected String determineBeanNameFromAnnotation(AnnotatedBeanDefinition annotatedDef) {AnnotationMetadata amd = annotatedDef.getMetadata();Set<String> types = amd.getAnnotationTypes();//AnnotatedBeanDefinition上面所有bean的类名String beanName = null;for (String type : types) {AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(amd, type);//注解的数据if (attributes != null) {Set<String> metaTypes = this.metaAnnotationTypesCache.computeIfAbsent(type, key -> {Set<String> result = amd.getMetaAnnotationTypes(key);//获取注解接口上的注解return (result.isEmpty() ? Collections.emptySet() : result);});if (isStereotypeWithNameValue(type, metaTypes, attributes)) {//检查是否存在生成beanName的名称Object value = attributes.get("value");//获取value的值if (value instanceof String) {String strVal = (String) value;//转成stringif (StringUtils.hasLength(strVal)) {//strVal有没有长度if (beanName != null && !strVal.equals(beanName)) {//如果beanName有值并且当前这个注解上的value不等于beanName就会报错throw new IllegalStateException("Stereotype annotations suggest inconsistent " +"component names: '" + beanName + "' versus '" + strVal + "'");}beanName = strVal;//赋值给beanName}}}}}return beanName;}

在进入isStereotypeWithNameValue中看看有那些注解支持设置自定义beanName

	protected boolean isStereotypeWithNameValue(String annotationType,Set<String> metaAnnotationTypes, @Nullable Map<String, Object> attributes) {boolean isStereotype = annotationType.equals(COMPONENT_ANNOTATION_CLASSNAME) ||//如果annotationType是Component类为truemetaAnnotationTypes.contains(COMPONENT_ANNOTATION_CLASSNAME) ||//如果父注解上有Component注解为trueannotationType.equals("javax.annotation.ManagedBean") ||//如果注解是是ManagedBean为trueannotationType.equals("javax.inject.Named");//如果注解是Named为truereturn (isStereotype && attributes != null && attributes.containsKey("value"));//isStereotype和atrributes不为空，并且atrributes有value这个值就返回true}

现在知道如果是Component注解或者父注解是Component，ManagedBean和Named可以设置beanName.

回到determineBeanNameFromeAnnotation中

@Nullableprotected String determineBeanNameFromAnnotation(AnnotatedBeanDefinition annotatedDef) {AnnotationMetadata amd = annotatedDef.getMetadata();Set<String> types = amd.getAnnotationTypes();//AnnotatedBeanDefinition上面所有bean的类名String beanName = null;for (String type : types) {AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(amd, type);//注解的数据if (attributes != null) {Set<String> metaTypes = this.metaAnnotationTypesCache.computeIfAbsent(type, key -> {Set<String> result = amd.getMetaAnnotationTypes(key);//获取注解接口上的注解return (result.isEmpty() ? Collections.emptySet() : result);});if (isStereotypeWithNameValue(type, metaTypes, attributes)) {//检查是否存在生成beanName的名称Object value = attributes.get("value");//获取value的值if (value instanceof String) {String strVal = (String) value;//转成stringif (StringUtils.hasLength(strVal)) {//strVal有没有长度if (beanName != null && !strVal.equals(beanName)) {//如果beanName有值并且当前这个注解上的value不等于beanName就会报错throw new IllegalStateException("Stereotype annotations suggest inconsistent " +"component names: '" + beanName + "' versus '" + strVal + "'");}beanName = strVal;//赋值给beanName}}}}}return beanName;}

有这么一行代码if (beanName != null && !strVal.equals(beanName)) 就是说如果beanName存在并且当前这个接口(Component,ManagedBean,Named)的value不为空就会报错

 报错

 

不会报错

如果没有自定义的beanName，就会调用

AnnotationBeanNameGenerator的buildDefaultBeanName这个方法

	protected String buildDefaultBeanName(BeanDefinition definition) {String beanClassName = definition.getBeanClassName();//获取class的名称包名Assert.state(beanClassName != null, "No bean class name set");String shortClassName = ClassUtils.getShortName(beanClassName);//获取class的名称去除包名return Introspector.decapitalize(shortClassName);//通过类名构造成普通java变量名}

进入Introspector.decapitalize

    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))){//如果第name的长度大于1并且第一个字母和第二个字母都是大写不处理直接返回return name;}char chars[] = name.toCharArray();chars[0] = Character.toLowerCase(chars[0]);//第一个字母变成小写return new String(chars);}

如果类名是Foobah变成foobah，类名是URL那beanName还是URL

到此beanName的构造过程全部结束