Spring IOC（5）AbstractBeanFactory
2020-12-13 本文已影响0人
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DefaultListableBeanFactory继承关系
在前面我们已经过了BeanFactory，ListableBeanFactory，ConfigurableBeanFactory，AutowireCapableBeanFactory，ConfigurableListableBeanFactory。
这里我们总结一下：
- ConfigurableBeanFactory：主要是parentBeanFactory的设置，添加ClassLoader，注册属性编辑器，类型转换器，添加BeanPostProcessor，以及bean的依赖注册和获取。
- AutowireCapableBeanFactory：主要是用于自动装配，Bean的创建、属性填充、连接(包括自动装配)、初始化和销毁，以及BeanPostProcessor的调用，还有resolveDependency方法声明。
- ConfigurableListableBeanFactory：主要是对BeanDefinition的解析获取功能，以及预实例化singleton的bean，还包括AutowireCandidate方法声明。
在看过这么多接口之后，终于有一个实现类了AbstractBeanFactory。
AbstractBeanFactory
AbstractBeanFactory实现了ConfigurableBeanFactory，还继承了FactoryBeanRegistrySupport（后面再讲）。到目前为止第一个跟BeanFactory相关的实现类，主要提供了getBean()的各种实现，核心方法是doGetBean()。
因为实现了ConfigurableBeanFactory，那么就会提供一些与实现相关的成员变量譬如parentBeanFactory，beanClassLoader，propertyEditorRegistrars，typeConverter，beanPostProcessors等。
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {
//提供了getBean的实现doGetBean()
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}
@Override
public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
return doGetBean(name, requiredType, null, false);
}
@Override
public Object getBean(String name, Object... args) throws BeansException {
return doGetBean(name, null, args, false);
}
public <T> T getBean(String name, @Nullable Class<T> requiredType, @Nullable Object... args)
throws BeansException {
return doGetBean(name, requiredType, args, false);
}
//实际获取bean的方法
protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
//转化name为beanName
final String beanName = transformedBeanName(name);
Object bean;
// getSingleton由DefaultSingletonBeanRegistry实现，用三级缓存解决循环依赖的问题
Object sharedInstance = getSingleton(beanName);
//如果缓存中存在该bean
if (sharedInstance != null && args == null) {
if (logger.isTraceEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
}
}
//如果是单例bean，则直接返回；如果是FactoryBean，则返回FactoryBean
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
//缓存中不存在该bean
else {
// 如果是prototype类型的，正在创建的bean，就直接报错
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
BeanFactory parentBeanFactory = getParentBeanFactory();
//检查BeanDefinition是否存在于该BeanFactory
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
String nameToLookup = originalBeanName(name);
//交由parentBeanFactory尝试getBean
if (parentBeanFactory instanceof AbstractBeanFactory) {
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else if (requiredType != null) {
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
else {
return (T) parentBeanFactory.getBean(nameToLookup);
}
}
if (!typeCheckOnly) {
//将该beanName放入alreadyCreated<set>中
markBeanAsCreated(beanName);
}
try {
//获得RootBeanDefinition
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
// 如果有dependsOn的bean，要先进行初始化
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dep : dependsOn) {
//判断该Dependent是否正在被创建
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
//将DependentBean注册到map中
registerDependentBean(dep, beanName);
try {
//调用getBean()来创建Dependent bean
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// 开始创建bean，DefaultSingletonBeanRegistry提供的getSingleton模板方法，接受一个ObjectFactory的函数来创建bean。
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
//createBean由子类AbstractAutowireCapableBeanFactory实现
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
destroySingleton(beanName);
throw ex;
}
});
//如果是单例bean，则直接返回；如果是FactoryBean，则返回FactoryBean
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
//创建prototype类型的bean
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
//原型bean每次getBean的时候都会去创建一个新的bean
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
//如果是单例bean，则直接返回；如果是FactoryBean，则返回FactoryBean
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
//customer scope的处理
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, () -> {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
});
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
}
if (requiredType != null && !requiredType.isInstance(bean)) {
try {
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
if (convertedBean == null) {
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
return convertedBean;
}
catch (TypeMismatchException ex) {
if (logger.isTraceEnabled()) {
logger.trace("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
return (T) bean;
}
@Override
public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
// Remove from old position, if any
this.beanPostProcessors.remove(beanPostProcessor);
// Track whether it is instantiation/destruction aware
if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) {
this.hasInstantiationAwareBeanPostProcessors = true;
}
if (beanPostProcessor instanceof DestructionAwareBeanPostProcessor) {
this.hasDestructionAwareBeanPostProcessors = true;
}
// Add to end of list
this.beanPostProcessors.add(beanPostProcessor);
}
//销毁bean
public void destroyBean(String beanName, Object beanInstance) {
destroyBean(beanName, beanInstance, getMergedLocalBeanDefinition(beanName));
}
//销毁bean
protected void destroyBean(String beanName, Object bean, RootBeanDefinition mbd) {
new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), getAccessControlContext()).destroy();
}
//根据beanName获取bean的class对象
@Nullable
protected Class<?> resolveBeanClass(final RootBeanDefinition mbd, String beanName, final Class<?>... typesToMatch)
throws CannotLoadBeanClassException {
try {
if (mbd.hasBeanClass()) {
return mbd.getBeanClass();
}
if (System.getSecurityManager() != null) {
return AccessController.doPrivileged((PrivilegedExceptionAction<Class<?>>) () ->
doResolveBeanClass(mbd, typesToMatch), getAccessControlContext());
}
else {
return doResolveBeanClass(mbd, typesToMatch);
}
}
catch (PrivilegedActionException pae) {
ClassNotFoundException ex = (ClassNotFoundException) pae.getException();
throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
}
catch (ClassNotFoundException ex) {
throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
}
catch (LinkageError err) {
throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), err);
}
}
//获取bean，如果是单例bean，则直接返回；如果是FactoryBean，则返回FactoryBean.getObject()
protected Object getObjectForBeanInstance(
Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) {
// Don't let calling code try to dereference the factory if the bean isn't a factory.
if (BeanFactoryUtils.isFactoryDereference(name)) {
if (beanInstance instanceof NullBean) {
return beanInstance;
}
if (!(beanInstance instanceof FactoryBean)) {
throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
}
}
// Now we have the bean instance, which may be a normal bean or a FactoryBean.
// If it's a FactoryBean, we use it to create a bean instance, unless the
// caller actually wants a reference to the factory.
if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
return beanInstance;
}
Object object = null;
if (mbd == null) {
object = getCachedObjectForFactoryBean(beanName);
}
if (object == null) {
// Return bean instance from factory.
FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
// Caches object obtained from FactoryBean if it is a singleton.
if (mbd == null && containsBeanDefinition(beanName)) {
mbd = getMergedLocalBeanDefinition(beanName);
}
boolean synthetic = (mbd != null && mbd.isSynthetic());
object = getObjectFromFactoryBean(factory, beanName, !synthetic);
}
return object;
}
---------抽象方法---------
//检查该BeanFactory里是否包含beanName对应的BeanDefinition
protected abstract boolean containsBeanDefinition(String beanName);
//根据beanName返回BeanDefinition
protected abstract BeanDefinition getBeanDefinition(String beanName) throws BeansException;
//根据给定的beanDefinition创建bean实例
protected abstract Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException;
}
