Spring初始化容器—实例化bean对象
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2022-05-21 22:10:42
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通过AbstractApplicationContext.refresh()方法调用finishBeanFactoryInitialization()方法进行bean的创建。
/**
* 完成bean的创建
* Finish the initialization of this context's bean factory,
* initializing all remaining singleton beans.
*/
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context.
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
beanFactory.setConversionService(
beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
beanFactory.freezeConfiguration();
//主要完成bean对象的实例化
// Instantiate all remaining (non-lazy-init) singletons.
beanFactory.preInstantiateSingletons();
}DefaultListableBeanFactory：主要完成bean的实例化、以及存储XmlBeanDefinitionReader解析resource注册到beanFactory中的BeanDefinition；数据结构如下：
public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
//.........................
//存储由XmlBeanDefinitionReader解析资源文件中的BeanDefinition
/** Map of bean definition objects, keyed by bean name */
private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>(64);
/** Map of singleton and non-singleton bean names keyed by dependency type */
private final Map<Class<?>, String[]> allBeanNamesByType = new ConcurrentHashMap<Class<?>, String[]>(64);
/** Map of singleton-only bean names keyed by dependency type */
private final Map<Class<?>, String[]> singletonBeanNamesByType = new ConcurrentHashMap<Class<?>, String[]>(64);
/** List of bean definition names, in registration order */
private final List<String> beanDefinitionNames = new ArrayList<String>();
/** Whether bean definition metadata may be cached for all beans */
private boolean configurationFrozen = false;
/** Cached array of bean definition names in case of frozen configuration */
private String[] frozenBeanDefinitionNames;
//.....................
}初始化单列bean对象，其中bean对象包括普通的bean对象和实现FactoryBean接口的bean对象；通过beanFactory获取FactoryBean对应的bean对象实际是通过FactoryBean.getObject()方法获取的。
@Override
public void preInstantiateSingletons() throws BeansException {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Pre-instantiating singletons in " + this);
}
List<String> beanNames;
synchronized (this.beanDefinitionMap) {
// Iterate over a copy to allow for init methods which in turn register new bean definitions.
// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
beanNames = new ArrayList<String>(this.beanDefinitionNames);
}
for (String beanName : beanNames) {
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
//判断bean类型
if (isFactoryBean(beanName)) {
//获取FactoryBean本身需要前缀“&”
final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
@Override
public Boolean run() {
return ((SmartFactoryBean<?>) factory).isEagerInit();
}
}, getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
getBean(beanName);
}
}
else {//普通bean的创建
getBean(beanName);
}
}
}
}
/**
* Return an instance, which may be shared or independent, of the specified bean.
* @param name the name of the bean to retrieve
* @param requiredType the required type of the bean to retrieve bean类型
* @param args arguments to use if creating a prototype using explicit arguments to a
* static factory method. It is invalid to use a non-null args value in any other case.
* args是prototype所需的参数
* @param typeCheckOnly whether the instance is obtained for a type check, 是否是类型检查
* not for actual use
* @return an instance of the bean
* @throws BeansException if the bean could not be created
*/
@SuppressWarnings("unchecked")
protected <T> T doGetBean(
final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
throws BeansException {
final String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {
if (logger.isDebugEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (args != null) {
// Delegation to parent with explicit args.
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else {
// No args -> delegate to standard getBean method.
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
}
if (!typeCheckOnly) {
markBeanAsCreated(beanName);//标记bean已创建
}
try {
//获取BeanDefinition
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
//检查BeanDefinition是否是Abstract，或者是否是Prototype等处理
checkMergedBeanDefinition(mbd, beanName, args);
//获取bean的依赖
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dependsOnBean : dependsOn) {
//判断循环依赖
if (isDependent(beanName, dependsOnBean)) {
throw new BeanCreationException("Circular depends-on relationship between '" +
beanName + "' and '" + dependsOnBean + "'");
}
registerDependentBean(dependsOnBean, beanName);
getBean(dependsOnBean);
}
}
//1、创建SingleBean
// Create bean instance.
if (mbd.isSingleton()) {
//创建单实例bean
sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
try {
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;
}
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
//2、创建PrototypeBean
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
//获取bean对象，bean为FactoryBean类型则，通过FactoryBean.getObject()获取，反之直接返回
//prototypeInstance
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
//其他类型的实例
else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
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;
}
}
//classType检查，若bean来下与ClassType不同，则进行强制转换
// Check if required type matches the type of the actual bean instance.
if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
try {
return getTypeConverter().convertIfNecessary(bean, requiredType);
}
catch (TypeMismatchException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to convert bean '" + name + "' to required type [" +
ClassUtils.getQualifiedName(requiredType) + "]", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
return (T) bean;
}
1、创建单实例bean，主要是依赖其父类SingletonBeanRegistry实现；SingletonBeanRegistry数据结构：
public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry {
/**
* Internal marker for a null singleton object:
* used as marker value for concurrent Maps (which don't support null values).
*/
protected static final Object NULL_OBJECT = new Object();
//缓存singleton对象
private final Map<String, Object> singletonObjects = new ConcurrentHashMap<String, Object>(64);
//缓存beanFactory
/** Cache of singleton factories: bean name --> ObjectFactory */
private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<String, ObjectFactory<?>>(16);
//缓存earlySingletonObjects，缓存创建的bean之前是否已被缓存过
/** Cache of early singleton objects: bean name --> bean instance */
private final Map<String, Object> earlySingletonObjects = new HashMap<String, Object>(16);
//缓存所有注册过的beanName
/** Set of registered singletons, containing the bean names in registration order */
private final Set<String> registeredSingletons = new LinkedHashSet<String>(64);
//当前正被创建的beanName
/** Names of beans that are currently in creation */
private final Set<String> singletonsCurrentlyInCreation =
Collections.newSetFromMap(new ConcurrentHashMap<String, Boolean>(16));
//创建被排除的beanname
/** Names of beans currently excluded from in creation checks */
private final Set<String> inCreationCheckExclusions =
Collections.newSetFromMap(new ConcurrentHashMap<String, Boolean>(16));
/** List of suppressed Exceptions, available for associating related causes */
private Set<Exception> suppressedExceptions;
/** Flag that indicates whether we're currently within destroySingletons */
private boolean singletonsCurrentlyInDestruction = false;
/** Disposable bean instances: bean name --> disposable instance */
private final Map<String, Object> disposableBeans = new LinkedHashMap<String, Object>();
/** Map between containing bean names: bean name --> Set of bean names that the bean contains */
private final Map<String, Set<String>> containedBeanMap = new ConcurrentHashMap<String, Set<String>>(16);
//缓存当前bean被所有其他bean依赖的集合
/** Map between dependent bean names: bean name --> Set of dependent bean names */
private final Map<String, Set<String>> dependentBeanMap = new ConcurrentHashMap<String, Set<String>>(64);
//与dependentBeanMap缓存方式相反，缓存当前bean所依赖的所有其他bean的集合
/** Map between depending bean names: bean name --> Set of bean names for the bean's dependencies */
private final Map<String, Set<String>> dependenciesForBeanMap = new ConcurrentHashMap<String, Set<String>>(64);
//..........................method..............
/**
* Return the (raw) singleton object registered under the given name,
* creating and registering a new one if none registered yet.
* @param beanName the name of the bean
* @param singletonFactory the ObjectFactory to lazily create the singleton
* with, if necessary
* @return the registered singleton object
*/
public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
Assert.notNull(beanName, "'beanName' must not be null");
synchronized (this.singletonObjects) {
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null) {
if (this.singletonsCurrentlyInDestruction) {
throw new BeanCreationNotAllowedException(beanName,
"Singleton bean creation not allowed while the singletons of this factory are in destruction " +
"(Do not request a bean from a BeanFactory in a destroy method implementation!)");
}
if (logger.isDebugEnabled()) {
logger.debug("Creating shared instance of singleton bean '" + beanName + "'");
}
beforeSingletonCreation(beanName);
boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
if (recordSuppressedExceptions) {
this.suppressedExceptions = new LinkedHashSet<Exception>();
}
try {
//创建bean
singletonObject = singletonFactory.getObject();
}
catch (BeanCreationException ex) {
if (recordSuppressedExceptions) {
for (Exception suppressedException : this.suppressedExceptions) {
ex.addRelatedCause(suppressedException);
}
}
throw ex;
}
finally {
if (recordSuppressedExceptions) {
this.suppressedExceptions = null;
}
afterSingletonCreation(beanName);
}
//将以创建的bean加入缓存singletonObjects中
addSingleton(beanName, singletonObject);
}
return (singletonObject != NULL_OBJECT ? singletonObject : null);
}
}
}转载于:https://my.oschina.net/u/1263326/blog/534155
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