第一节 参考
spring架构，Bean创建前的定义过程参考<spring源码分析之架构和Refresh>
第二节 架构
如下图
三步操作:创建对象，填充成员，调用初始化方法
三种回调:InstantiationAwareBeanPostProcessor创建对象回调,BeanPostProcessor初始化成员时回调,InitializingBean业务bean的初始化方法
第三节 源码
一.入口
protected <T> T doGetBean(
final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
throws BeansException {
//转换bean的名称。主要是对工厂bean，去掉&,取出真实名称
final String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
/*
先在DefaultSingletonBeanRegistry.singletonObjects，DefaultSingletonBeanRegistry.earlySingletonObjects，
DefaultSingletonBeanRegistry.singletonFactories里面检查是否已经创建过, 已经创建过或者正在创建过程中的直接返回,处理循环依赖,
代码在后面分析
*/
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 + "'");
}
}
//如果是工厂Bean,调用factory.getObject()解析真实对象返回,代码在后面分析
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
//如果bean是原型模式，且正在创建过程中，运行到这里代表循环依赖了，抛出异常
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
//检查bean的定义是否在父BeanFactory中有定义，如果有，通过父BeanFactory创建,还没见过这种用法?
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) {
//把bean的名称放到AbstractBeanFactory#alreadyCreated成员中，标记正在创建过程中.
markBeanAsCreated(beanName);
}
try {
//获取bean的定义
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
//如果bean定义检查是abstract虚拟类，抛出异常
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
//如果bean有依赖类，先创建依赖类的实例
if (dependsOn != null) {
//遍历依赖类
for (String dep : dependsOn) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
//创建依赖类的实例
getBean(dep);
}
}
// Create bean instance.
/*创建单例模式的bean.在createBean创建完之后，调用getSingleton()方法把bean放到
DefaultSingletonBeanRegistry#singletonObjects里面，同时从DefaultSingletonBeanRegistry#singletonFactories中移除，
循环依赖处理完成 */
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
try {
//实际完成创建bean的操作,代码在后面分析
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;
}
}
});
//创建工厂bean的对象
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
else if (mbd.isPrototype()) {
//创建原型模式的bean对象,每次都是new一个新对象
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
//创建除了单例，原型模式的bean对象
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, 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;
}
}
// Check if required type matches the type of the actual bean instance.
//如果创建出来的bean不是bean定义中Class类型的，抛出异常
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;
}二.处理循环依赖
如果已经创建的直接返回，正在创建中的处理循环依赖.
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
synchronized (this.singletonObjects) {
singletonObject = this.earlySingletonObjects.get(beanName);
if (singletonObject == null && allowEarlyReference) {
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
if (singletonFactory != null) {
//后面九中,实例化后，还没有填充前，会先put到singletonFactory中.这里直接返回，不用重复创建，循环依赖.
singletonObject = singletonFactory.getObject();
this.earlySingletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
}
}
}
}
return (singletonObject != NULL_OBJECT ? singletonObject : null);
}三.创建FactoryBean的对象
AbstractBeanFactory#getObjectForBeanInstance()代码如下:
protected Object getObjectForBeanInstance(
Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {
// Don't let calling code try to dereference the factory if the bean isn't a factory.
//判断是不是工厂类型的bean，不是抛异常
if (BeanFactoryUtils.isFactoryDereference(name) && !(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());
//调用factory.getObject()获取bean的真实对象
object = getObjectFromFactoryBean(factory, beanName, !synthetic);
}
return object;
}四.创建Bean
protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
if (logger.isDebugEnabled()) {
logger.debug("Creating instance of bean '" + beanName + "'");
}
RootBeanDefinition mbdToUse = mbd;
// Make sure bean class is actually resolved at this point, and
// clone the bean definition in case of a dynamically resolved Class
// which cannot be stored in the shared merged bean definition.
//调用AbstractBeanFactory#doResolveBeanClass()解析bean的Class类型,代码在后面5分析
Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
mbdToUse = new RootBeanDefinition(mbd);
mbdToUse.setBeanClass(resolvedClass);
}
// Prepare method overrides.
try {
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}
try {
// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
//调用各种InstantiationAwareBeanPostProcessor的postProcessBeforeInitialization()方法,代码在后面6分析
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
if (bean != null) {
return bean;
}
}
catch (Throwable ex) {
throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
"BeanPostProcessor before instantiation of bean failed", ex);
}
//实际创建Bean对象的重要方法,代码在后面7分析
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
if (logger.isDebugEnabled()) {
logger.debug("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}五.解析bean的Class类型
private Class<?> doResolveBeanClass(RootBeanDefinition mbd, Class<?>... typesToMatch)
throws ClassNotFoundException {
//这里获取到的是AppClassLoader
ClassLoader beanClassLoader = getBeanClassLoader();
ClassLoader classLoaderToUse = beanClassLoader;
//这里不进去
if (!ObjectUtils.isEmpty(typesToMatch)) {
// When just doing type checks (i.e. not creating an actual instance yet),
// use the specified temporary class loader (e.g. in a weaving scenario).
ClassLoader tempClassLoader = getTempClassLoader();
if (tempClassLoader != null) {
classLoaderToUse = tempClassLoader;
if (tempClassLoader instanceof DecoratingClassLoader) {
DecoratingClassLoader dcl = (DecoratingClassLoader) tempClassLoader;
for (Class<?> typeToMatch : typesToMatch) {
dcl.excludeClass(typeToMatch.getName());
}
}
}
}
//获取类的完全路径名称
String className = mbd.getBeanClassName();
if (className != null) {
//调用StandardBeanExpressionResolver#evaluate()处理类路径名称，通配符处理?
Object evaluated = evaluateBeanDefinitionString(className, mbd);
if (!className.equals(evaluated)) {
// A dynamically resolved expression, supported as of 4.2...
if (evaluated instanceof Class) {
return (Class<?>) evaluated;
}
else if (evaluated instanceof String) {
return ClassUtils.forName((String) evaluated, classLoaderToUse);
}
else {
throw new IllegalStateException("Invalid class name expression result: " + evaluated);
}
}
// When resolving against a temporary class loader, exit early in order
// to avoid storing the resolved Class in the bean definition.
if (classLoaderToUse != beanClassLoader) {
return ClassUtils.forName(className, classLoaderToUse);
}
}
//调用ClassLoader#loadClass()或者Class.forName生成bean的Class对象
return mbd.resolveBeanClass(beanClassLoader);
}六.回调BeanPostProcessor
回调各种InstantiationAwareBeanPostProcessor的postProcessBeforeInstantiation()
protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
Object bean = null;
if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
// Make sure bean class is actually resolved at this point.
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
//如果是FactoryBean,获取真实类型
Class<?> targetType = determineTargetType(beanName, mbd);
if (targetType != null) {
//遍历InstantiationAwareBeanPostProcessor,调用postProcessBeforeInstantiation
//aop在这里处理，后面新开贴分析
bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);
if (bean != null) {
/* 如果在InstantiationAwareBeanPostProcessor中已经实例化，直接调用InstantiationAwareBeanPostProcessor#postProcessAfterInstantiation回调 */
bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
}
}
}
mbd.beforeInstantiationResolved = (bean != null);
}
return bean;
}七.实际创建bean的核心方法
AbstractAutowireCapableBeanFactory#doCreateBean(),代码如下:
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
throws BeanCreationException {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
//如果Bean是单例的，从FactoryBean缓存中移除
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
//完成Bean的实例化，生成对象，属性没有填充,重要方法,需要判断调用哪个构造方法,代码在后面8分析
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
//遍历所有MergedBeanDefinitionPostProcessor的实现类，回调它的postProcessMergedBeanDefinition()方法.
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Post-processing of merged bean definition failed", ex);
}
mbd.postProcessed = true;
}
}
// Eagerly cache singletons to be able to resolve circular references
// even when triggered by lifecycle interfaces like BeanFactoryAware.
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
if (logger.isDebugEnabled()) {
logger.debug("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
//在填充属性前,标记自己被创建中,提前put到singletonFactories里面,处理循环依赖,在前面的二中取出,代码在后面9分析
addSingletonFactory(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
return getEarlyBeanReference(beanName, mbd, bean);
}
});
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
//IOC填充注入bean对象的成员属性,重要方法,在后面10分析
populateBean(beanName, mbd, instanceWrapper);
if (exposedObject != null) {
/* 调用bean的初始化方法。在此之前，bean的构造方法，成员属性都已经注入完成.代码在后面十五分析. */
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
}
catch (Throwable ex) {
if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
throw (BeanCreationException) ex;
}
else {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
}
}
if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);
if (earlySingletonReference != null) {
if (exposedObject == bean) {
exposedObject = earlySingletonReference;
}
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
for (String dependentBean : dependentBeans) {
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
actualDependentBeans.add(dependentBean);
}
}
if (!actualDependentBeans.isEmpty()) {
throw new BeanCurrentlyInCreationException(beanName,
"Bean with name '" + beanName + "' has been injected into other beans [" +
StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
"] in its raw version as part of a circular reference, but has eventually been " +
"wrapped. This means that said other beans do not use the final version of the " +
"bean. This is often the result of over-eager type matching - consider using " +
"'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
}
}
}
}
// Register bean as disposable.
try {
//把bean注册到DefaultSingletonBeanRegistry#disposableBeans的map中，表示可以被析构
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}八.实例化Bean对象
AbstractAutowireCapableBeanFactory#createBeanInstance()方法,代码如下:
protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
// Make sure bean class is actually resolved at this point.
//获取bean的实际类型
Class<?> beanClass = resolveBeanClass(mbd, beanName);
//只能注入public的类。
if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
}
//如果是FactoryMethod的类，通过FactoryMethod实例化.
if (mbd.getFactoryMethodName() != null) {
return instantiateUsingFactoryMethod(beanName, mbd, args);
}
// Shortcut when re-creating the same bean...
boolean resolved = false;
boolean autowireNecessary = false;
if (args == null) {
synchronized (mbd.constructorArgumentLock) {
if (mbd.resolvedConstructorOrFactoryMethod != null) {
resolved = true;
autowireNecessary = mbd.constructorArgumentsResolved;
}
}
}
if (resolved) {
if (autowireNecessary) {
//autowire注解的类创建对象
return autowireConstructor(beanName, mbd, null, null);
}
else {
return instantiateBean(beanName, mbd);
}
}
// Need to determine the constructor...
/* 判断调用哪个构造方法创建对象,普通的bean走到这里.如果是SmartInstantiationAwareBeanPostProcessor类型.回调determineCandidateConstructors方法
返回Constructor.InstantiationAwareBeanPostProcessorAdapter类有这个回调，但是空实现.AutowiredAnnotationBeanPostProcessor类通过这个接口做lookupMethod处理.
对于普通的bean,这里Constructor返回null.
*/
Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
if (ctors != null ||
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {
return autowireConstructor(beanName, mbd, ctors, args);
}
// No special handling: simply use no-arg constructor.
//普通bean进入这里,先调用Class#getDeclaredConstructor()获取无参的构造方法,再调用Constructor#newInstance()创建实例
//,然后把创建的Bean实例放到BeanWrapperImpl封装对象中.
return instantiateBean(beanName, mbd);
}九.处理循环依赖
提前暴露到DefaultSingletonBeanRegistry#singletonFactories中.
protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory) {
Assert.notNull(singletonFactory, "Singleton factory must not be null");
synchronized (this.singletonObjects) {
if (!this.singletonObjects.containsKey(beanName)) {
//放到singletonFactories中,在前面二中，如果循环依赖了，直接从singletonFactories中返回，不会重复创建
this.singletonFactories.put(beanName, singletonFactory);
this.earlySingletonObjects.remove(beanName);
this.registeredSingletons.add(beanName);
}
}
}十.填充注入Bean对象的成员属性
protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) {
PropertyValues pvs = mbd.getPropertyValues();
//实例化的bean对象为空，直接返回
if (bw == null) {
if (!pvs.isEmpty()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// Skip property population phase for null instance.
return;
}
}
// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
// state of the bean before properties are set. This can be used, for example,
// to support styles of field injection.
boolean continueWithPropertyPopulation = true;
//遍历所有InstantiationAwareBeanPostProcessor接口的实现类,调用它的postProcessAfterInstantiation()方法
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
continueWithPropertyPopulation = false;
break;
}
}
}
}
if (!continueWithPropertyPopulation) {
return;
}
//如果注入类型是byName.xml里面的bean默认是AbstractBeanDefinition#AUTOWIRE_NO.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);
if (hasInstAwareBpps || needsDepCheck) {
PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
if (hasInstAwareBpps) {
/*在后面11分析.
遍历所有InstantiationAwareBeanPostProcessor接口的实现类,回调它的postProcessPropertyValues方法.
autowired的注解在AutowiredAnnotationBeanPostProcessor#postProcessPropertyValues()方法处理注入.
@Resource注解在CommonAnnotationBeanPostProcessor#postProcessPropertyValues()处理.
*/
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvs == null) {
return;
}
}
}
}
if (needsDepCheck) {
checkDependencies(beanName, mbd, filteredPds, pvs);
}
}
applyPropertyValues(beanName, mbd, bw, pvs);
}十一.注入Autowired成员属性
进入AutowiredAnnotationBeanPostProcessor#postProcessPropertyValues()方法,代码如下:
public PropertyValues postProcessPropertyValues(
PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException {
//获取带有@Autowired注解的所有成员属性.
InjectionMetadata metadata = findAutowiringMetadata(beanName, bean.getClass(), pvs);
try {
/* 注入上面获取到的成员,即遍历这些成员，每一个都调用AutowiredAnnotationBeanPostProcessor.AutowiredFieldElement#inject()方法,创建这些成员的对象并且初始化,代码在下面12分析 */
metadata.inject(bean, beanName, pvs);
}
catch (Throwable ex) {
throw new BeanCreationException(beanName, "Injection of autowired dependencies failed", ex);
}
return pvs;
}十二.注入填充单个属性.
进入代码AutowiredAnnotationBeanPostProcessor.AutowiredFieldElement#inject()方法,代码如下:
protected void inject(Object bean, String beanName, PropertyValues pvs) throws Throwable {
//获取要Autowired注入的成员
Field field = (Field) this.member;
try {
Object value;
if (this.cached) {
value = resolvedCachedArgument(beanName, this.cachedFieldValue);
}
else {
//创建DependencyDescriptor对象封装描述这个成员的信息,比如所在类,类型.
DependencyDescriptor desc = new DependencyDescriptor(field, this.required);
desc.setContainingClass(bean.getClass());
Set<String> autowiredBeanNames = new LinkedHashSet<String>(1);
TypeConverter typeConverter = beanFactory.getTypeConverter();
/* 调用DefaultListableBeanFactory#resolveDependency()解析这个成员，成员可能是map,list，普通bean,代码在后面13分析 */
value = beanFactory.resolveDependency(desc, beanName, autowiredBeanNames, typeConverter);
synchronized (this) {
if (!this.cached) {
if (value != null || this.required) {
this.cachedFieldValue = desc;
/*记录依赖关系,放到DefaultSingletonBeanRegistry#dependentBeanMap()中记录，key是成员，value是依赖这个成员的bean,反向记录.
同时放到DefaultSingletonBeanRegistry#dependenciesForBeanMap,正向记录 */
registerDependentBeans(beanName, autowiredBeanNames);
if (autowiredBeanNames.size() == 1) {
String autowiredBeanName = autowiredBeanNames.iterator().next();
if (beanFactory.containsBean(autowiredBeanName)) {
if (beanFactory.isTypeMatch(autowiredBeanName, field.getType())) {
this.cachedFieldValue = new RuntimeBeanReference(autowiredBeanName);
}
}
}
}
else {
this.cachedFieldValue = null;
}
this.cached = true;
}
}
}
if (value != null) {
//把解析到的成员对象赋值到bean属性里面
ReflectionUtils.makeAccessible(field);
field.set(bean, value);
}
}
catch (Throwable ex) {
throw new BeanCreationException("Could not autowire field: " + field, ex);
}
}
}十三.注入单个成员属性，创建bean的成员的对象
进入DefaultListableBeanFactory#resolveDependency()方法,实际调用下面这个方法处理.
public Object doResolveDependency(DependencyDescriptor descriptor, String beanName,
Set<String> autowiredBeanNames, TypeConverter typeConverter) throws BeansException {
//获取注入的成员Class对象
Class<?> type = descriptor.getDependencyType();
//获取注入成员的值,普通bean这里为null
Object value = getAutowireCandidateResolver().getSuggestedValue(descriptor);
if (value != null) {
if (value instanceof String) {
String strVal = resolveEmbeddedValue((String) value);
BeanDefinition bd = (beanName != null && containsBean(beanName) ? getMergedBeanDefinition(beanName) : null);
value = evaluateBeanDefinitionString(strVal, bd);
}
TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
return (descriptor.getField() != null ?
converter.convertIfNecessary(value, type, descriptor.getField()) :
converter.convertIfNecessary(value, type, descriptor.getMethodParameter()));
}
//注入数组类型的成员
if (type.isArray()) {
Class<?> componentType = type.getComponentType();
DependencyDescriptor targetDesc = new DependencyDescriptor(descriptor);
targetDesc.increaseNestingLevel();
Map<String, Object> matchingBeans = findAutowireCandidates(beanName, componentType, targetDesc);
if (matchingBeans.isEmpty()) {
if (descriptor.isRequired()) {
raiseNoSuchBeanDefinitionException(componentType, "array of " + componentType.getName(), descriptor);
}
return null;
}
if (autowiredBeanNames != null) {
autowiredBeanNames.addAll(matchingBeans.keySet());
}
TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
Object result = converter.convertIfNecessary(matchingBeans.values(), type);
if (getDependencyComparator() != null && result instanceof Object[]) {
Arrays.sort((Object[]) result, adaptDependencyComparator(matchingBeans));
}
return result;
}
//注入集合类型的成员
else if (Collection.class.isAssignableFrom(type) && type.isInterface()) {
Class<?> elementType = descriptor.getCollectionType();
if (elementType == null) {
if (descriptor.isRequired()) {
throw new FatalBeanException("No element type declared for collection [" + type.getName() + "]");
}
return null;
}
DependencyDescriptor targetDesc = new DependencyDescriptor(descriptor);
targetDesc.increaseNestingLevel();
Map<String, Object> matchingBeans = findAutowireCandidates(beanName, elementType, targetDesc);
if (matchingBeans.isEmpty()) {
if (descriptor.isRequired()) {
raiseNoSuchBeanDefinitionException(elementType, "collection of " + elementType.getName(), descriptor);
}
return null;
}
if (autowiredBeanNames != null) {
autowiredBeanNames.addAll(matchingBeans.keySet());
}
TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
Object result = converter.convertIfNecessary(matchingBeans.values(), type);
if (getDependencyComparator() != null && result instanceof List) {
Collections.sort((List<?>) result, adaptDependencyComparator(matchingBeans));
}
return result;
}
//注入Map
else if (Map.class.isAssignableFrom(type) && type.isInterface()) {
Class<?> keyType = descriptor.getMapKeyType();
if (String.class != keyType) {
if (descriptor.isRequired()) {
throw new FatalBeanException("Key type [" + keyType + "] of map [" + type.getName() +
"] must be [java.lang.String]");
}
return null;
}
Class<?> valueType = descriptor.getMapValueType();
if (valueType == null) {
if (descriptor.isRequired()) {
throw new FatalBeanException("No value type declared for map [" + type.getName() + "]");
}
return null;
}
DependencyDescriptor targetDesc = new DependencyDescriptor(descriptor);
targetDesc.increaseNestingLevel();
Map<String, Object> matchingBeans = findAutowireCandidates(beanName, valueType, targetDesc);
if (matchingBeans.isEmpty()) {
if (descriptor.isRequired()) {
raiseNoSuchBeanDefinitionException(valueType, "map with value type " + valueType.getName(), descriptor);
}
return null;
}
if (autowiredBeanNames != null) {
autowiredBeanNames.addAll(matchingBeans.keySet());
}
return matchingBeans;
}
else {
/* 注入普通的bean,遍历所有的DefaultListableBeanFactory#beanDefinitionNames,查找该成员类型的对象，找到bean定义,这里对同一个interface,可能有多个实现类,
每个都调用getBean()创建对象并初始化,代码在后面分析.具体调用栈如下图 */
Map<String, Object> matchingBeans = findAutowireCandidates(beanName, type, descriptor);
if (matchingBeans.isEmpty()) {
if (descriptor.isRequired()) {
raiseNoSuchBeanDefinitionException(type, "", descriptor);
}
return null;
}
if (matchingBeans.size() > 1) {
String primaryBeanName = determineAutowireCandidate(matchingBeans, descriptor);
if (primaryBeanName == null) {
//找到多个相同类型的bean，未指定优先级，报错.
throw new NoUniqueBeanDefinitionException(type, matchingBeans.keySet());
}
if (autowiredBeanNames != null) {
autowiredBeanNames.add(primaryBeanName);
}
return matchingBeans.get(primaryBeanName);
}
// We have exactly one match.
Map.Entry<String, Object> entry = matchingBeans.entrySet().iterator().next();
if (autowiredBeanNames != null) {
autowiredBeanNames.add(entry.getKey());
}
return entry.getValue();
}
}
十四.创建bean的成员的对象并初始化
protected Map<String, Object> findAutowireCandidates(
String beanName, Class<?> requiredType, DependencyDescriptor descriptor) {
/* 遍历所有的DefaultListableBeanFactory#beanDefinitionNames,查找该成员类型的对象，找到bean名称,普通不是接口的bean，这里返回该成员有的名称 */
String[] candidateNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
this, requiredType, true, descriptor.isEager());
Map<String, Object> result = new LinkedHashMap<String, Object>(candidateNames.length);
for (Class<?> autowiringType : this.resolvableDependencies.keySet()) {
if (autowiringType.isAssignableFrom(requiredType)) {
Object autowiringValue = this.resolvableDependencies.get(autowiringType);
autowiringValue = AutowireUtils.resolveAutowiringValue(autowiringValue, requiredType);
if (requiredType.isInstance(autowiringValue)) {
result.put(ObjectUtils.identityToString(autowiringValue), autowiringValue);
break;
}
}
}
for (String candidateName : candidateNames) {
if (!isSelfReference(beanName, candidateName) && isAutowireCandidate(candidateName, descriptor)) {
//重要!遍历对找到的每一个候选bean名称，调用getBean()方法创建bean的对象,并且初始化，这里完成bean成员的创建
result.put(candidateName, getBean(candidateName));
}
}
if (result.isEmpty()) {
DependencyDescriptor fallbackDescriptor = descriptor.forFallbackMatch();
for (String candidateName : candidateNames) {
if (!candidateName.equals(beanName) && isAutowireCandidate(candidateName, fallbackDescriptor)) {
result.put(candidateName, getBean(candidateName));
}
}
}
return result;
}十五.调用bean的初始化方法
在此之前，bean的构造方法，成员属性都已经注入完成
protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {
AccessController.doPrivileged(new PrivilegedAction<Object>() {
@Override
public Object run() {
invokeAwareMethods(beanName, bean);
return null;
}
}, getAccessControlContext());
}
else {
invokeAwareMethods(beanName, bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
//遍历所有的BeanPostProcessor对象，回调它的postProcessBeforeInitialization()方法.
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
//如果是InitializingBean对象，回调它的afterPropertiesSet()方法.
//如果bean定义了initMethod调用它的初始化方法.
invokeInitMethods(beanName, wrappedBean, mbd);
}
catch (Throwable ex) {
throw new BeanCreationException(
(mbd != null ? mbd.getResourceDescription() : null),
beanName, "Invocation of init method failed", ex);
}
if (mbd == null || !mbd.isSynthetic()) {
//遍历所有的BeanPostProcessor对象，回调它的postProcessAfterInitialization()方法.
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}
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