今天我们讲解spring 启动过程中最核心方法，我们计划分多篇讲解，今天解析该方法的主干核心，后几篇我们解析该方法相关的分支方法（为啥啊？因为这个方法太重要了！），废话少说，看源码！
1、来到 AbstractApplicationContext extends DefaultResourceLoader implements ConfigurableApplicationContext 类的
refresh() 方法
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
try {
//删除以前解析过的源码
/*
* 这个方法是spring中最重要的方法，没有之一
* 因此这个方法一定要详细分析，主要有一下几点功能：
* 1、bean实例化过程，实例化所有的(非惰性初始化)单例。
* 2、ioc 容器，循环依赖注入
* 3、类中各种注解的支持
* 4、BeanPostProcessor的执行
* 5、Aop动态代理的入口处
* */
finishBeanFactoryInitialization(beanFactory);//点击进入
// Last step: publish corresponding event.
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
//设置类型转换器
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));
}
//如果没有bean后处理器，注册一个默认的嵌入式值解析器
//(例如PropertyPlaceholderConfigurer bean)以前注册过:
//此时，主要用于解析注释属性值。
//先简单看看
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// 尽早初始化LoadTimeWeaverAware bean，以便尽早注册它们的转换器。先简单看看
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// 停止使用临时类加载器进行类型匹配。先简单看看
beanFactory.setTempClassLoader(null);
// 允许缓存所有的bean定义元数据，不期望有进一步的更改。先简单看看
beanFactory.freezeConfiguration();
//重点看这个方法，实例化所有剩余的(非惰性初始化)单例。
beanFactory.preInstantiateSingletons();//点击进入
}
2、ctrl+t 进入 DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable 类中
@Override
public void preInstantiateSingletons() throws BeansException {
if (logger.isTraceEnabled()) {
logger.trace("Pre-instantiating singletons in " + this);
}
//前几篇 讲解 xml解析时讲过，把所有beanName都缓存到beanDefinitionNames了
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// 触发所有非惰性单例bean的初始化...
for (String beanName : beanNames) {
//把父BeanDefinition里面的属性拿到子子类BeanDefinition中，可以进去先看看，不难
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
//如果不是抽象的，单例的，非懒加载的就实例化
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
//判断bean是否实现了FactoryBean接口，这里自己看看，后面会详细讲解
if (isFactoryBean(beanName)) {
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
if (bean instanceof FactoryBean) {
final FactoryBean<?> factory = (FactoryBean<?>) bean;
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
((SmartFactoryBean<?>) factory)::isEagerInit,
getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
getBean(beanName);
}
}
}
else {
//主要核心从这里进入，看看实例化过程，点击进入
getBean(beanName);
}
}
}
// 所有适用的bean触发初始化后回调...
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}3、进入 AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory 中的
getBean方法@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);//继续进入，进入最最核心方法
}protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
final String beanName = transformedBeanName(name);
System.out.println("====beanName=="+beanName+"===instance begin====");
Object bean;
//首先从缓存中拿实例
Object sharedInstance = getSingleton(beanName);
//如果缓存里面能拿到实例
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 + "'");
}
}
//该方法是FactoryBean接口的调用入口
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
//如果singletonObjects缓存里面没有，则往下看
//如果是scope 是Prototype的，校验是否有出现循环依赖，如果有则直接报错
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// 检查这个工厂中是否存在bean定义
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
//如果没有，则效验父类
String nameToLookup = originalBeanName(name);
if (parentBeanFactory instanceof AbstractBeanFactory) {
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
// 使用显式参数委托给父进程
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else if (requiredType != null) {
// 没有参数 -> 委托给标准的getBean方法
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
else {
return (T) parentBeanFactory.getBean(nameToLookup);
}
}
if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}
try {
//父子BeanDefinition合并
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
//获取依赖对象属性，依赖对象要先实例化，即保证当前bean所依赖的bean先初始化。
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
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);
try {
//实例化
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
//着重看，创建单例对象
if (mbd.isSingleton()) {//这里采用java8 lambda 表达式，函数式接口，取代以前的匿名内部类。
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);//ctrl+t 点击进入
}
catch (BeansException ex) {
//从单例缓存中显式删除实例:它可能已经被放在那里了
//先被创建进程，以允许循环引用解析。
//还要删除接收到该bean的临时引用的所有 bean对象。
destroySingleton(beanName);
throw ex;
}
});
//改方法是FactoryBean接口的调用入口
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
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);
}
//改方法是FactoryBean接口的调用入口
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
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);
}
});
//改方法是FactoryBean接口的调用入口
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;
}
}
// 检查所需的类型是否与实际bean实例的类型相匹配
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;
}5、进入 AbstractAutowireCapableBeanFactory extends AbstractBeanFactory implements AutowireCapableBeanFactory
@Override
protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
if (logger.isTraceEnabled()) {
logger.trace("Creating instance of bean '" + beanName + "'");
}
RootBeanDefinition mbdToUse = mbd;
//确保此时bean类已经解析，并且在动态解析类的情况下，克隆bean定义，不能共享的合并到bean中。
Class<?> resolvedClass = resolveBeanClass(mbd, beanName);//通过反射获取类 以后细讲
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
mbdToUse = new RootBeanDefinition(mbd);
mbdToUse.setBeanClass(resolvedClass);
}
// 准备方法覆盖
try {
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}
try {
/*
* TargetSource接口的运用，可以在用改一个类实现该接口，然后在里面定义实例化对象的方式，然后返回
* 也就是说不需要spring帮助我们实例化对象，这里可以直接返回实例本身
* 给beanpostprocessor一个机会来返回代理而不是目标bean实例， 这个代码简单看看，实际开发过程中很少用到。
* */
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);
}
try {
//主要看这个方法，非常重要，点击进入
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
if (logger.isTraceEnabled()) {
logger.trace("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {
// A previously detected exception with proper bean creation context already,
// or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry.
throw ex;
}
catch (Throwable ex) {
throw new BeanCreationException(
mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex);
}
}来到这个核心方法 doCreateBean，这个方法里面有多个主要分支，我们一一揭晓。
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)
throws BeanCreationException {
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);//先从缓存中删除
}
if (instanceWrapper == null) {
//创建实例后包装到BeanWrapper 中,这里就是bean的实例化过程，重点看，点击进入
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
final Object bean = instanceWrapper.getWrappedInstance();//再获取到这个对象
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// 允许后置处理器修改合并bean
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
//CommonAnnotationBeanPostProcessor 支持了@PostConstruct，@PreDestroy,@Resource注解
//AutowiredAnnotationBeanPostProcessor 支持 @Autowired,@Value注解
//BeanPostProcessor接口的典型运用，这里要着重理解这个接口
//对类中注解的自动装配过程，这里是非常重要的一个分支 ，点击进入
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Post-processing of merged bean definition failed", ex);
}
mbd.postProcessed = true;
}
}
//立刻缓存单例以便能够解析循环引用
//甚至当由生命周期接口(如BeanFactoryAware)触发时也是如此。
//单例bean是否提前暴露
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
if (logger.isTraceEnabled()) {
logger.trace("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
//这里着重理解，对理解循环依赖帮助非常大， 添加三级缓存,对象提前暴露，很重要，后面会讲，
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
Object exposedObject = bean;
try {
//ioc di，依赖注入的核心方法，点击进入
populateBean(beanName, mbd, instanceWrapper);
//bean 实例化+ioc依赖注入完以后的调用，非常重要
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<>(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 {
//注册bean销毁时的类DisposableBeanAdapter
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
点击 instanceWrapper = createBeanInstance(beanName, mbd, args);来到--->
protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
// Make sure bean class is actually resolved at this point.
//反射拿到Class对象
Class<?> beanClass = resolveBeanClass(mbd, beanName);
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());
}
Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
if (instanceSupplier != null) {
return obtainFromSupplier(instanceSupplier, beanName);
}
//如果有FactoryMethodName属性
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) {
return autowireConstructor(beanName, mbd, null, null);
}
else {
return instantiateBean(beanName, mbd);
}
}
// Candidate constructors for autowiring?
//寻找当前正在实例化的bean中有@Autowired注解的构造函数
Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
if (ctors != null || mbd.getResolvedAutowireMode() == AUTOWIRE_CONSTRUCTOR ||
mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {
//如果ctors不为空，就说明构造函数上有@Autowired注解
return autowireConstructor(beanName, mbd, ctors, args);
}
// Preferred constructors for default construction?
ctors = mbd.getPreferredConstructors();
if (ctors != null) {
return autowireConstructor(beanName, mbd, ctors, null);
}
//无参构造函数的实例化,大部分的实例是采用的无参构造函数的方式实例化,里面通过反射获取构造器，然后实例化对象，最后包装到 // //beanWarpper 中返回，对象实例化结束，以后这个分支方法还会细讲，感兴趣的小伙伴，可以先提前预习。
return instantiateBean(beanName, mbd);
}
点击 applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName); 来到-->
protected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class<?> beanType, String beanName) { //获取所有的beanPostProcessors 接口类型的对象，循环遍历；判断是否是MergedBeanDefinitionPostProcessor 类型的；
//如果是就循环调用 postProcessMergedBeanDefinition 方法，该方法是对有 @Autowired、@Value、@PostConstruct、@PreDestroy、@Resource等常用注解的方法或属性进行收集装配并封装成对象。
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof MergedBeanDefinitionPostProcessor) {
MergedBeanDefinitionPostProcessor bdp = (MergedBeanDefinitionPostProcessor) bp;
bdp.postProcessMergedBeanDefinition(mbd, beanType, beanName);//ctrl+t 如图显示-->
}
}
}
这里最主要涉及到 CommonAnnotationBeanPostProcessor 和AutowiredAnnotationBeanPostProcessor 类，
前者 CommonAnnotationBeanPostProcessor完成了@Resource @PostConstruct 和@PreDestory注解的属性或 者方法的收集和 支持。后者AutowiredAnnotationBeanPostProcessor 类，对@Autowired @Value注解的属性和方法的收集。收集过程基本上跟@Resource 注解的收集差不多。这里主要举例分析CommonAnnotationBeanPostProcessor 点击进入
6、来到 CommonAnnotationBeanPostProcessor extends InitDestroyAnnotationBeanPostProcessor implements InstantiationAwareBeanPostProcessor, BeanFactoryAware, Serializable 类中
/*
* 1、扫描类里面的属性或者方法
* 2、判断属性或者方法上面是否有@PostConstruct @PreDestroy @Resource注解
* 3、如果有注解的属性或者方法，包装成一个类
* */
@Override
public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
//扫描@PostConstruct @PreDestroy
super.postProcessMergedBeanDefinition(beanDefinition, beanType, beanName);
//扫描@Resource,扫描属性和方法上面是否有@Resource注解，如果有则收集起来封装成对象，以后细讲。
InjectionMetadata metadata = findResourceMetadata(beanName, beanType, null);
metadata.checkConfigMembers(beanDefinition);
}
另外 看一下构造方法，一眼就看到对@PostConstruct @PreDestroy注解的支持
public CommonAnnotationBeanPostProcessor() {
setOrder(Ordered.LOWEST_PRECEDENCE - 3);
setInitAnnotationType(PostConstruct.class);
setDestroyAnnotationType(PreDestroy.class);
ignoreResourceType("javax.xml.ws.WebServiceContext");
}
7、点 populateBean(beanName, mbd, instanceWrapper);来到-->
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
if (bw == null) {
if (mbd.hasPropertyValues()) {
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;
//这里是依赖注入的设置，是否允许依赖注入设，写接口可以让所有类都不能依赖注入
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
//是否需要，依赖注入
continueWithPropertyPopulation = false;
break;
}
}
}
}
if (!continueWithPropertyPopulation) {
return;
}
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
if (mbd.getResolvedAutowireMode() == AUTOWIRE_BY_NAME || mbd.getResolvedAutowireMode() == AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
if (mbd.getResolvedAutowireMode() == AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
if (mbd.getResolvedAutowireMode() == AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);
PropertyDescriptor[] filteredPds = null;
//重点看这个if代码块，重要程度 5
if (hasInstAwareBpps) {
if (pvs == null) {
pvs = mbd.getPropertyValues();
}
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
//依赖注入核心过程，@Autowired的支持，ctrl+t 进入
PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
//老版本这个完成依赖注入过程，@Autowired的支持
pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
return;
}
}
pvs = pvsToUse;
}
}
}
if (needsDepCheck) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
checkDependencies(beanName, mbd, filteredPds, pvs);
}
//这个方法标签做依赖注入的代码实现，复杂且无用
if (pvs != null) {
applyPropertyValues(beanName, mbd, bw, pvs);
}
}
8、ctrl+t 点击 ibp.postProcessProperties 来到AutowiredAnnotationBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter
implements MergedBeanDefinitionPostProcessor, PriorityOrdered, BeanFactoryAware
@Override
public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) {
//先取到有autowird 的
InjectionMetadata metadata = findAutowiringMetadata(beanName, bean.getClass(), pvs);
try {
metadata.inject(bean, beanName, pvs);//点击
}
catch (BeanCreationException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanCreationException(beanName, "Injection of autowired dependencies failed", ex);
}
return pvs;
}
9、来到 InjectionMetadata
public void inject(Object target, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable {
Collection<InjectedElement> checkedElements = this.checkedElements;
Collection<InjectedElement> elementsToIterate =
(checkedElements != null ? checkedElements : this.injectedElements);
if (!elementsToIterate.isEmpty()) {
for (InjectedElement element : elementsToIterate) {
if (logger.isTraceEnabled()) {
logger.trace("Processing injected element of bean '" + beanName + "': " + element);
}
if(element.isField) {
Field field = (Field)element.member;
}
element.inject(target, beanName, pvs);//循环遍历，点击进入
}
}
}
protected void inject(Object target, @Nullable String requestingBeanName, @Nullable PropertyValues pvs)
throws Throwable {
if (this.isField) {
Field field = (Field) this.member;
ReflectionUtils.makeAccessible(field);
field.set(target, getResourceToInject(target, requestingBeanName));//这里完成了依赖注入
}
else {
if (checkPropertySkipping(pvs)) {
return;
}
try {
Method method = (Method) this.member;
ReflectionUtils.makeAccessible(method);
method.invoke(target, getResourceToInject(target, requestingBeanName));
}
catch (InvocationTargetException ex) {
throw ex.getTargetException();
}
}
}
时间关系今天写到这里，方法主干已经写完，下一篇开始分析相关分支方法，比如循环依赖注入、AOP入口、IOC之后的一些方法调用、bean的销毁等等，敬请期待。大家有不懂地方可以留言！