Spring BeanDefinitionRegistry 接口
Spring BeanDefinitionRegistry 接口Registry 登记/注册 顾名思义, 该接口设计的目的是用于保存和管理 Bean定义描述(BeanDefinition)
org.springframework.beans.factory.support.BeanDefinitionRegistry
package org.springframework.beans.factory.support;
import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.core.AliasRegistry;
/**
* Interface for registries that hold bean definitions, for example RootBeanDefinition
* and ChildBeanDefinition instances. Typically implemented by BeanFactories that
* internally work with the AbstractBeanDefinition hierarchy.
*
* Registry 登记/注册 顾名思义 该接口设计的目的是用于保存和管理 Bean定义描述(BeanDefinition), 例如:RootBeanDefinition 和 ChildBeanDefinition 实例
*
* <p>This is the only interface in Spring's bean factory packages that encapsulates
* <i>registration</i> of bean definitions. The standard BeanFactory interfaces
* only cover access to a <i>fully configured factory instance</i>.
*
* <p>Spring's bean definition readers expect to work on an implementation of this
* interface. Known implementors within the Spring core are DefaultListableBeanFactory
* and GenericApplicationContext.
*
* @author Juergen Hoeller
* @since 26.11.2003
* @see org.springframework.beans.factory.config.BeanDefinition
* @see AbstractBeanDefinition
* @see RootBeanDefinition
* @see ChildBeanDefinition
* @see DefaultListableBeanFactory
* @see org.springframework.context.support.GenericApplicationContext
* @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
* @see PropertiesBeanDefinitionReader
*/
public interface BeanDefinitionRegistry extends AliasRegistry {
/**
* Register a new bean definition with this registry.
* Must support RootBeanDefinition and ChildBeanDefinition.
*
* 根据名称注册一个新的 BeanDefinition
* @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.
*
* 根据名称移除一个 BeanDefinition
* @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.
*
* 根据名称获取 BeanDefinition
* @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.
* 检查给定名称是否已存在
* @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 bean definition for the given name is overridable,
* i.e. whether {@link #registerBeanDefinition} would successfully return
* against an existing definition of the same name.
* <p>The default implementation returns {@code true}.
*
*判定给定的名称是否允许覆盖它的 BeanDefinition
*
* @param beanName the name to check
* @return whether the definition for the given bean name is overridable
* @since 6.1
*/
default boolean isBeanDefinitionOverridable(String beanName) {
return true;
}
/**
* 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);
}DefaultListableBeanFactory 的实现
大多数情况下, 我们项目的 BeanFactory 的实例是 DefaultListableBeanFactory, 它也是一个 BeanDefinitionRegistry
org.springframework.beans.factory.support.DefaultListableBeanFactory#registerBeanDefinition
public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
.........
/**
* 注册一个 BeanDefinition 的方法
*/
@Override
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 abd) {
try {
abd.validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}
// 获取一下是否有这个 bean 的 BeanDefinition
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
// 如果有 且 不允许覆盖, 则抛出 BeanDefinitionOverrideException
if (!isBeanDefinitionOverridable(beanName)) {
throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
}
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
if (logger.isInfoEnabled()) {
logger.info("Overriding user-defined bean definition for bean '" + beanName +
"' with a framework-generated bean definition: replacing [" +
existingDefinition + "] with [" + beanDefinition + "]");
}
}
else if (!beanDefinition.equals(existingDefinition)) {
if (logger.isDebugEnabled()) {
logger.debug("Overriding bean definition for bean '" + beanName +
"' with a different definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
else {
if (logger.isTraceEnabled()) {
logger.trace("Overriding bean definition for bean '" + beanName +
"' with an equivalent definition: replacing [" + existingDefinition +
"] with [" + beanDefinition + "]");
}
}
this.beanDefinitionMap.put(beanName, beanDefinition);
}
else {
if (isAlias(beanName)) {
//判断下, 别名是否覆盖.
String aliasedName = canonicalName(beanName);
if (!isBeanDefinitionOverridable(aliasedName)) {
if (containsBeanDefinition(aliasedName)) {// alias for existing bean definition
throw new BeanDefinitionOverrideException(
beanName, beanDefinition, getBeanDefinition(aliasedName));
}
else {// alias pointing to non-existing bean definition
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition for bean '" + beanName +
"' since there is already an alias for bean '" + aliasedName + "' bound.");
}
}
else {
removeAlias(beanName);
}
}
if (hasBeanCreationStarted()) {
//bean 是否已经开始创建中. 后面再研究, 不是这个分支
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
this.beanDefinitionMap.put(beanName, beanDefinition);
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
updatedDefinitions.addAll(this.beanDefinitionNames);
updatedDefinitions.add(beanName);
this.beanDefinitionNames = updatedDefinitions;
removeManualSingletonName(beanName);
}
}
else {
// 放到 beanDefinitionMap, key 是 beanName; value 是 beanDefinition;
// Still in startup registration phase
this.beanDefinitionMap.put(beanName, beanDefinition);
// 别名 添加到 beanDefinitionNames
this.beanDefinitionNames.add(beanName);
removeManualSingletonName(beanName);
}
this.frozenBeanDefinitionNames = null;
}
if (existingDefinition != null || containsSingleton(beanName)) {
resetBeanDefinition(beanName);
}
else if (isConfigurationFrozen()) {
clearByTypeCache();
}
}
/**
* 移除一个 BeanDefinition 的方法
*/
@Override
public void removeBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
Assert.hasText(beanName, "'beanName' must not be empty");
//从 beanDefinitionMap 中移除
BeanDefinition bd = this.beanDefinitionMap.remove(beanName);
if (bd == null) {
if (logger.isTraceEnabled()) {
logger.trace("No bean named '" + beanName + "' found in " + this);
}
throw new NoSuchBeanDefinitionException(beanName);
}
//bean 是否已经开始创建中
if (hasBeanCreationStarted()) {
// Cannot modify startup-time collection elements anymore (for stable iteration)
synchronized (this.beanDefinitionMap) {
List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames);
updatedDefinitions.remove(beanName);
this.beanDefinitionNames = updatedDefinitions;
}
}
else {
//从 beanDefinitionNames 中移除
// Still in startup registration phase
this.beanDefinitionNames.remove(beanName);
}
this.frozenBeanDefinitionNames = null;
resetBeanDefinition(beanName);
}
........ 对于 DefaultListableBeanFactory 的实现主要就是使用两个集合存起来:
/**
* 这个 Map 存储所有已注册 BeanDefinition, 其中 key是bean主要name, value 是 BeanDefinition
*/
private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);
/**
* 这个list 存储所有的 bean definition 名称
*/
private volatile List<String> beanDefinitionNames = new ArrayList<>(256);
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