Spring版本
5.2.5.RELEASE
参考
源码解读
BeanDefinitionRegistry继承了AliasRegistry接口，其核心子类有三个：
SimpleBeanDefinitionRegistryDefaultListableBeanFactoryGenericApplicationContext
1 AliasRegistry
public interface AliasRegistry {
/**
* Given a name, register an alias for it.
* @param name the canonical name
* @param alias the alias to be registered
* @throws IllegalStateException if the alias is already in use
* and may not be overridden
*/
void registerAlias(String name, String alias);
/**
* Remove the specified alias from this registry.
* @param alias the alias to remove
* @throws IllegalStateException if no such alias was found
*/
void removeAlias(String alias);
/**
* Determine whether the given name is defined as an alias
* (as opposed to the name of an actually registered component).
* @param name the name to check
* @return whether the given name is an alias
*/
boolean isAlias(String name);
/**
* Return the aliases for the given name, if defined.
* @param name the name to check for aliases
* @return the aliases, or an empty array if none
*/
String[] getAliases(String name);
}
该接口定义了四个方法：
-
registerAlias：为name注册alias别名 -
removeAlias：移除别名 -
isAlias：判断name是否被定义为别名 -
getAliases：获取name对应的所有别名
2 BeanDefinitionRegistry
public interface BeanDefinitionRegistry extends AliasRegistry {
/**
* Register a new bean definition with this registry.
* Must support RootBeanDefinition and ChildBeanDefinition.
* @param beanName the name of the bean instance to register
* @param beanDefinition definition of the bean instance to register
* @throws BeanDefinitionStoreException if the BeanDefinition is invalid
* @throws BeanDefinitionOverrideException if there is already a BeanDefinition
* for the specified bean name and we are not allowed to override it
* @see GenericBeanDefinition
* @see RootBeanDefinition
* @see ChildBeanDefinition
*/
void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException;
/**
* Remove the BeanDefinition for the given name.
* @param beanName the name of the bean instance to register
* @throws NoSuchBeanDefinitionException if there is no such bean definition
*/
void removeBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;
/**
* Return the BeanDefinition for the given bean name.
* @param beanName name of the bean to find a definition for
* @return the BeanDefinition for the given name (never {@code null})
* @throws NoSuchBeanDefinitionException if there is no such bean definition
*/
BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;
/**
* Check if this registry contains a bean definition with the given name.
* @param beanName the name of the bean to look for
* @return if this registry contains a bean definition with the given name
*/
boolean containsBeanDefinition(String beanName);
/**
* Return the names of all beans defined in this registry.
* @return the names of all beans defined in this registry,
* or an empty array if none defined
*/
String[] getBeanDefinitionNames();
/**
* Return the number of beans defined in the registry.
* @return the number of beans defined in the registry
*/
int getBeanDefinitionCount();
/**
* Determine whether the given bean name is already in use within this registry,
* i.e. whether there is a local bean or alias registered under this name.
* @param beanName the name to check
* @return whether the given bean name is already in use
*/
boolean isBeanNameInUse(String beanName);
}
BeanDefinitionRegistry继承自AliasRegistry，提供了一系列关于beanDefinition注册的接口定义
3 SimpleBeanDefinitionRegistry
public class SimpleBeanDefinitionRegistry extends SimpleAliasRegistry implements BeanDefinitionRegistry {
/** Map of bean definition objects, keyed by bean name. */
private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(64);
@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
Assert.hasText(beanName, "'beanName' must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
this.beanDefinitionMap.put(beanName, beanDefinition);
}
@Override
public void removeBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
if (this.beanDefinitionMap.remove(beanName) == null) {
throw new NoSuchBeanDefinitionException(beanName);
}
}
@Override
public BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
BeanDefinition bd = this.beanDefinitionMap.get(beanName);
if (bd == null) {
throw new NoSuchBeanDefinitionException(beanName);
}
return bd;
}
@Override
public boolean containsBeanDefinition(String beanName) {
return this.beanDefinitionMap.containsKey(beanName);
}
@Override
public String[] getBeanDefinitionNames() {
return StringUtils.toStringArray(this.beanDefinitionMap.keySet());
}
@Override
public int getBeanDefinitionCount() {
return this.beanDefinitionMap.size();
}
@Override
public boolean isBeanNameInUse(String beanName) {
return isAlias(beanName) || containsBeanDefinition(beanName);
}
}
SimpleBeanDefinitionRegistry是BeanDefinitionRegistry的一个简单实现，可以看到
SimpleBeanDefinitionRegistry内部维护了一个ConcurrentHashMap对象beanDefinitionMap，beanDefinition的注册、移除等相关操作其实就是对beanDefinitionMap的操作。
4 DefaultListableBeanFactory
DefaultListableBeanFactory，ConfigurableListableBeanFactory（其实就是 BeanFactory ） 和BeanDefinitionRegistry接口的默认实现：一个基于BeanDefinition元数据的完整 bean 工厂。所以相对于SimpleBeanDefinitionRegistry而言，DefaultListableBeanFactory则是一个具有注册功能的完整 Bean 工厂。它同样是用ConcurrentHashMap数据结构来存储注册的 BeanDefinition。具体逻辑可以查看《Spring源码解析（六）-解析bean标签》 3.1 节
5 GenericApplicationContext
@Override
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
this.beanFactory.registerBeanDefinition(beanName, beanDefinition);
}
@Override
public void removeBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
this.beanFactory.removeBeanDefinition(beanName);
}
对于类GenericApplicationContext，查看源码你会发现他实现注册、注销功能都是委托DefaultListableBeanFactory实现的。
总结
BeanRegistry的逻辑是比较简单，不外乎就是将信息保存到一个map中，并没有想象中的复杂和高大上。
