spring源码（8）注册解析的BeanDefinition

对于配置文件解析完之后，我们得到了beanDefinition。下一步就是注册。 同样，注册操作委托给BeanDefinitionReaderUtils.registerBeanDefinition。

public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {

//使用beanName做唯一标识注册
String beanName = definitionHolder.getBeanName();
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
//注册所有的别名
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
for (String aliase : aliases) {
registry.registerAlias(beanName, aliase);
}
}
}

一、使用beanName做唯一标识注册

对于BeanDefinition的注册，spring将beanName，放入list集合beanDefinitionNames。BeanDefinition放入Map集合beanDefinitionMap中。

public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {

Assert.hasText(beanName, "Bean name must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");

if (beanDefinition instanceof AbstractBeanDefinition) {
try {
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}

BeanDefinition oldBeanDefinition;

//对beanDefinitionMap增加同步操作
synchronized (this.beanDefinitionMap) {
oldBeanDefinition = this.beanDefinitionMap.get(beanName);
if (oldBeanDefinition != null) {
//如果配置了bean不允许被覆盖，则抛出异常
if (!this.allowBeanDefinitionOverriding) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
"': There is already [" + oldBeanDefinition + "] bound.");
}
else {
if (this.logger.isInfoEnabled()) {
this.logger.info("Overriding bean definition for bean '" + beanName +
"': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]");
}
}
}
else {
//记录BeanName
this.beanDefinitionNames.add(beanName);
this.frozenBeanDefinitionNames = null;
}
//记录beanDefinition
this.beanDefinitionMap.put(beanName, beanDefinition);
}

if (oldBeanDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
}

二、注册所有的别名

别名存放在Map集合aliasMap中

public void registerAlias(String name, String alias) {
Assert.hasText(name, "'name' must not be empty");
Assert.hasText(alias, "'alias' must not be empty");
//如果alias与beanName相同，删除原有的alias
if (alias.equals(name)) {
this.aliasMap.remove(alias);
}
else {
//若不允许覆盖，别名已经被其他bean使用，则抛出异常
if (!allowAliasOverriding()) {
String registeredName = this.aliasMap.get(alias);
if (registeredName != null && !registeredName.equals(name)) {
throw new IllegalStateException("Cannot register alias '" + alias + "' for name '" +
name + "': It is already registered for name '" + registeredName + "'.");
}
}
//循环检查
checkForAliasCircle(name, alias);
this.aliasMap.put(alias, name);
}
}