前言
接着Spring5IOC容器解析--createBean()方法分析上我们继续解析创建 bean 实例的剩下内容。
正文
首先，我们回到 doCreateBean 方法中，doCreateBean()方法主要是根据 beanName、mbd、args，使用对应的策略创建 bean 实例，并返回包装类 BeanWrapper。
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
// 1.新建Bean包装类
BeanWrapper instanceWrapper = null;
//如果RootBeanDefinition是单例的，则移除未完成的FactoryBean实例的缓存
if (mbd.isSingleton()) {
// 2.如果是FactoryBean，则需要先移除未完成的FactoryBean实例的缓存
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
// 3.根据beanName、mbd、args，使用对应的策略创建Bean实例，并返回包装类BeanWrapper
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
// 4.拿到创建好的Bean实例
final Object bean = instanceWrapper.getWrappedInstance();
// 5.拿到Bean实例的类型
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
// 6.应用后置处理器MergedBeanDefinitionPostProcessor，允许修改MergedBeanDefinition，
// Autowired注解、Value注解正是通过此方法实现注入类型的预解析
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.
// 7.判断是否需要提早曝光实例：单例 && 允许循环依赖 && 当前bean正在创建中
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");
}
// 8.提前曝光beanName的ObjectFactory，用于解决循环引用
// 8.1 应用后置处理器SmartInstantiationAwareBeanPostProcessor，允许返回指定bean的早期引用，若没有则直接返回bean
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
// Initialize the bean instance.
// 初始化bean实例。
Object exposedObject = bean;
try {
// 9.对bean进行属性填充；其中，可能存在依赖于其他bean的属性，则会递归初始化依赖的bean实例
populateBean(beanName, mbd, instanceWrapper);
// 10.对bean进行初始化
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) {
// 11.如果允许提前曝光实例，则进行循环依赖检查
Object earlySingletonReference = getSingleton(beanName, false);
// 11.1 earlySingletonReference只有在当前解析的bean存在循环依赖的情况下才会不为空
if (earlySingletonReference != null) {
if (exposedObject == bean) {
// 11.2 如果exposedObject没有在initializeBean方法中被增强，则不影响之前的循环引用
exposedObject = earlySingletonReference;
}
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
// 11.3 如果exposedObject在initializeBean方法中被增强 && 不允许在循环引用的情况下使用注入原始bean实例
// && 当前bean有被其他bean依赖
// 11.4 拿到依赖当前bean的所有bean的beanName数组
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
for (String dependentBean : dependentBeans) {
// 11.5 尝试移除这些bean的实例，因为这些bean依赖的bean已经被增强了，他们依赖的bean相当于脏数据
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
// 11.6 移除失败的添加到 actualDependentBeans
actualDependentBeans.add(dependentBean);
}
}
if (!actualDependentBeans.isEmpty()) {
// 11.7 如果存在移除失败的，则抛出异常，因为存在bean依赖了“脏数据”
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 " +
"'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example.");
}
}
}
}
// Register bean as disposable.
try {
// 12.注册用于销毁的bean，执行销毁操作的有三种：自定义destroy方法、DisposableBean接口、DestructionAwareBeanPostProcessor
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
// 13.完成创建并返回
return exposedObject;
}
}
- earlySingletonReference 只有在当前解析的 bean 存在循环依赖的情况下才会不为空。
因为如果不是循环依赖，只会在完全创建完 bean 实例才会添加到 singletonObjects 缓存。此时，我们正在创建 bean 的过程中，还没有完全创建完，singletonObjects 缓存是肯定没有当前 beanName 的；而如果不存在循环引用，从 doGetBean 方法开始，getSingleton 方法只会在最初 doGetBean 方法里调用一次，不存在循环引用，也就用不到提前曝光的 ObjectFactory 来创建 bean 对象，从而 earlySingletonObjects 缓存肯定也是没有 beanName 的 bean 实例对象的，所以必然返回空。
- 注册用于销毁的 bean，执行销毁操作的有三种：自定义 destroy 方法、DisposableBean 接口、DestructionAwareBeanPostProcessor。
applyMergedBeanDefinitionPostProcessors
- 应用后置处理器 MergedBeanDefinitionPostProcessor，允许修改MergedBeanDefinition，Autowired注解、Value注解正是通过此方法实现注入类型的预解析。
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
protected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class<?> beanType, String beanName) {
// 1.获取BeanFactory中已注册的BeanPostProcessor
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof MergedBeanDefinitionPostProcessor) {
// 2.调用MergedBeanDefinitionPostProcessor的postProcessMergedBeanDefinition方法
MergedBeanDefinitionPostProcessor bdp = (MergedBeanDefinitionPostProcessor) bp;
//重点关注AutowiredAnnotationBeanPostProcessor，该类会把@Autowired等标记的
//需要依赖注入的成员变量或者方法实例给记录下来，方便后续populateBean使用
bdp.postProcessMergedBeanDefinition(mbd, beanType, beanName);
}
}
}
}
addSingletonFactory
-
提前曝光beanName的ObjectFactory，用于解决循环引用。
-
应用后置处理器SmartInstantiationAwareBeanPostProcessor，允许返回指定bean的早期引用，若没有则直接返回bean。
public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry {
/** Cache of singleton objects: bean name to bean instance. */
//一级缓存：单例对象缓存池，beanName->Bean，其中存储的就是实例化，属性赋值成功之后的单例对象
private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
/** Cache of singleton factories: bean name to ObjectFactory. */
//三级缓存：单例工厂的缓存，beanName->ObjectFactory，添加进去的时候实例还未具备属性
// 用于保存beanName和创建bean的工厂之间的关系map，单例Bean在创建之初过早的暴露出去的Factory，
// 为什么采用工厂方式，是因为有些Bean是需要被代理的，总不能把代理前的暴露出去那就毫无意义了
private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<>(16);
/** Cache of early singleton objects: bean name to bean instance. */
//二级缓存：早期的单例对象，beanName->Bean，其中存储的是实例化之后，属性未赋值的单例对象
// 执行了工厂方法生产出来的Bean，bean被放进去之后，
// 那么当bean在创建过程中，就可以通过getBean方法获取到
private final Map<String, Object> earlySingletonObjects = new HashMap<>(16);
/** Set of registered singletons, containing the bean names in registration order. */
private final Set<String> registeredSingletons = new LinkedHashSet<>(256);
protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory) {
Assert.notNull(singletonFactory, "Singleton factory must not be null");
synchronized (this.singletonObjects) {
// 1.如果beanName不存在于singletonObjects缓存中
if (!this.singletonObjects.containsKey(beanName)) {
//往三级缓存里添加
// 2.将beanName和singletonFactory注册到singletonFactories缓存（beanName -> 该beanName的单例工厂）
this.singletonFactories.put(beanName, singletonFactory);
//清除此Bean在二级缓存里的缓存信息
// 3.移除earlySingletonObjects缓存中的beanName（beanName -> beanName的早期单例对象）
this.earlySingletonObjects.remove(beanName);
//这里为了记录注册单例的顺序
// 4.将beanName注册到registeredSingletons缓存（已经注册的单例集合）
this.registeredSingletons.add(beanName);
}
}
}
}
在Spring5IOC容器解析--refresh()方法分析中，通过提前曝光的 ObjectFactory 获得 “不完整” 的 bean 实例，从而解决循环引用的问题，ObjectFactory 就是通过这边的 singletonFactories缓存来进行曝光的。
getEarlyBeanReference
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) {
Object exposedObject = bean;
// 1.如果bean不为空 && mbd不是合成 && 存在InstantiationAwareBeanPostProcessors
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
// 2.应用所有SmartInstantiationAwareBeanPostProcessor，调用getEarlyBeanReference方法
if (bp instanceof SmartInstantiationAwareBeanPostProcessor) {
SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp;
// 3.允许SmartInstantiationAwareBeanPostProcessor返回指定bean的早期引用
exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName);
}
}
}
// 4.返回要作为bean引用公开的对象，如果没有SmartInstantiationAwareBeanPostProcessor修改，则返回的是入参的bean对象本身
return exposedObject;
}
}
populateBean
- 对 bean 进行属性填充；其中，可能存在依赖于其他 bean 的属性，则会递归初始化依赖的 bean 实例。
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
// bw为空时的处理
if (bw == null) {
// 如果bw为空，属性不为空，抛异常，无法将属性值应用于null实例
if (mbd.hasPropertyValues()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// Skip property population phase for null instance.
// 如果bw为空，属性也为空，则跳过
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.
// 给InstantiationAwareBeanPostProcessors最后一次机会在属性注入前修改Bean的属性值，也可以控制是否继续填充Bean
// 具体通过调用postProcessAfterInstantiation方法，如果调用返回false,表示不必继续进行依赖注入，直接返回
// 主要是让用户可以自定义属性注入。比如用户实现一个 InstantiationAwareBeanPostProcessor 类型的后置处理器，
// 并通过 postProcessAfterInstantiation 方法向 bean 的成员变量注入自定义的信息。
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
// 如果mbd不是合成的 && 存在InstantiationAwareBeanPostProcessor，则遍历处理InstantiationAwareBeanPostProcessor
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
// 在bean实例化后，属性填充之前被调用，允许修改bean的属性，如果返回false，则跳过之后的属性填充
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
return;
}
}
}
}
// pvs是一个MutablePropertyValues实例，里面实现了PropertyValues接口，
// 提供属性的读写操作实现，同时可以通过调用构造函数实现深拷贝
//获取BeanDefinition里面为Bean设置上的属性值
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
// 根据Bean配置的依赖注入方式完成注入，默认是0，即不走以下逻辑，所有的依赖注入都需要在xml文件中有显式的配置
// 如果设置了相关的依赖装配方式，会遍历Bean中的属性，根据类型或名称来完成相应注入，无需额外配置
int resolvedAutowireMode = mbd.getResolvedAutowireMode();
if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
// 根据beanName进行autowiring自动装配处理
if (resolvedAutowireMode == AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
//根据Bean的类型进行autowiring自动装配处理
if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
//BeanFactory是否注册过InstantiationAwareBeanPostProcessors
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
//是否进行依赖检查，默认为false
boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);
PropertyDescriptor[] filteredPds = null;
//注册过InstantiationAwareBeanPostProcessors 或者 需要依赖检查
if (hasInstAwareBpps) {
if (pvs == null) {
pvs = mbd.getPropertyValues();
}
// 7.1 应用后置处理器InstantiationAwareBeanPostProcessor
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
//在这里会对@Autowired标记的属性进行依赖注入
//调用AutowiredAnnotationBeanPostProcessor的postProcessProperties
PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
// 对解析完但未设置的属性再进行处理
pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
return;
}
}
pvs = pvsToUse;
}
}
}
// 依赖检查，对应depend-on属性，3.0已经弃用此属性
if (needsDepCheck) {
// 过滤出所有需要进行依赖检查的属性编辑器
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
checkDependencies(beanName, mbd, filteredPds, pvs);
}
if (pvs != null) {
//最终将属性注入到Bean的Wrapper实例里，这里的注入主要是供
//显式配置了autowiredbyName或者ByType的属性注入，
//针对注解来讲，由于在AutowiredAnnotationBeanPostProcessor已经完成了注入，
//所以此处不执行
applyPropertyValues(beanName, mbd, bw, pvs);
}
}
}
应用后置处理器 InstantiationAwareBeanPostProcessor 的方法 postProcessPropertyValues，进行属性填充前的再次处理。现在最常用的 @Autowire 属性注入就是这边注入依赖的 bean 实例对象，具体实现在 AutowiredAnnotationBeanPostProcessor的postProcessProperties方法完成注入。
将所有 PropertyValues 中的属性填充到 bean 中。
autowireByName
- 解析 autowireByName 的注入
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
protected void autowireByName(
String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) {
//获取要注入的非简单类型的属性名称
String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw);
for (String propertyName : propertyNames) {
// 检测是否存在与 propertyName 相关的 bean 或 BeanDefinition。
// 若存在，则调用 BeanFactory.getBean 方法获取 bean 实例
if (containsBean(propertyName)) {
// 从容器中获取相应的 bean 实例
Object bean = getBean(propertyName);
// 将解析出的 bean 存入到属性值列表pvs中
pvs.add(propertyName, bean);
// 注册依赖关系到缓存（beanName依赖propertyName）
registerDependentBean(propertyName, beanName);
if (logger.isTraceEnabled()) {
logger.trace("Added autowiring by name from bean name '" + beanName +
"' via property '" + propertyName + "' to bean named '" + propertyName + "'");
}
}
else {
if (logger.isTraceEnabled()) {
logger.trace("Not autowiring property '" + propertyName + "' of bean '" + beanName +
"' by name: no matching bean found");
}
}
}
}
}
unsatisfiedNonSimpleProperties
- 获取要注入的非简单类型的属性名称
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
/*
* 获取非简单类型属性的名称，且该属性未被配置在配置文件中。
* bean class="org.springframework.aop.framework.ProxyFactoryBean">
* <property name="target">
<ref parent="accountService"/>
* </property>
* </bean>
* Spring 认为的"简单类型"属性有哪些，如下：
* 1. CharSequence 接口的实现类，比如 String
* 2. Enum
* 3. Date
* 4. URI/URL
* 5. Number 的继承类，比如 Integer/Long
* 6. byte/short/int... 等基本类型
* 7. Locale
* 8. 以上所有类型的数组形式，比如 String[]、Date[]、int[] 等等
*
* 除了要求非简单类型的属性外，还要求属性未在配置文件中配置过，也就是 pvs.contains(pd.getName()) = false。
*/
protected String[] unsatisfiedNonSimpleProperties(AbstractBeanDefinition mbd, BeanWrapper bw) {
Set<String> result = new TreeSet<>();
// 1.拿到mdb的属性值
PropertyValues pvs = mbd.getPropertyValues();
// 2.拿到bw的PropertyDescriptors
PropertyDescriptor[] pds = bw.getPropertyDescriptors();
// 3.遍历bw的PropertyDescriptors
for (PropertyDescriptor pd : pds) {
// 4.pd用于写入属性值的方法不为空 && pd不是从依赖性检查中排除的bean属性 && pd不包含在pvs里
// && pd的属性类型不是“简单”属性（基础类型、枚举、Number等）
// 4.1 isSimpleProperty: 判断属性是不是“简单”属性
if (pd.getWriteMethod() != null && !isExcludedFromDependencyCheck(pd) && !pvs.contains(pd.getName()) &&
!BeanUtils.isSimpleProperty(pd.getPropertyType())) {
// 4.2 符合条件，则添加pd的name到result中
result.add(pd.getName());
}
}
return StringUtils.toStringArray(result);
}
}
isSimpleProperty
- 判断属性是不是 “简单” 属性
public static boolean isSimpleProperty(Class<?> type) {
Assert.notNull(type, "'type' must not be null");
// clazz是简单值类型 || （ clazz是数组 && clazz的组件类型为简单值类型）
// getComponentType：返回数组的组件类型，例如: String[] 返回 String.class，如果是非数组，则返回null
return isSimpleValueType(type) || (type.isArray() && isSimpleValueType(type.getComponentType()));
}
public static boolean isSimpleValueType(Class<?> type) {
return (Void.class != type && void.class != type &&
(ClassUtils.isPrimitiveOrWrapper(type) ||
Enum.class.isAssignableFrom(type) ||
CharSequence.class.isAssignableFrom(type) ||
Number.class.isAssignableFrom(type) ||
Date.class.isAssignableFrom(type) ||
Temporal.class.isAssignableFrom(type) ||
URI.class == type ||
URL.class == type ||
Locale.class == type ||
Class.class == type));
}
public static boolean isPrimitiveOrWrapper(Class<?> clazz) {
Assert.notNull(clazz, "Class must not be null");
// clazz为基础类型 或者 clazz是基础类型的封装类
return (clazz.isPrimitive() || isPrimitiveWrapper(clazz));
}
public static boolean isPrimitiveWrapper(Class<?> clazz) {
Assert.notNull(clazz, "Class must not be null");
// 检查clazz是否为8种基础类型的包装类
// primitiveWrapperTypeMap缓存包含8种基础类型和包装类的映射，例如：Integer.class -> int.class
return primitiveWrapperTypeMap.containsKey(clazz);
}
static {
primitiveWrapperTypeMap.put(Boolean.class, boolean.class);
primitiveWrapperTypeMap.put(Byte.class, byte.class);
primitiveWrapperTypeMap.put(Character.class, char.class);
primitiveWrapperTypeMap.put(Double.class, double.class);
primitiveWrapperTypeMap.put(Float.class, float.class);
primitiveWrapperTypeMap.put(Integer.class, int.class);
primitiveWrapperTypeMap.put(Long.class, long.class);
primitiveWrapperTypeMap.put(Short.class, short.class);
primitiveWrapperTypeMap.put(Void.class, void.class);
}
containsBean
- 检测是否存在与 propertyName 相关的 bean 或 BeanDefinition是否存在。
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {
@Override
public boolean containsBean(String name) {
// 1.将name转换为真正的beanName
String beanName = transformedBeanName(name);
// 2.检查singletonObjects缓存和beanDefinitionMap缓存中是否存在beanName
if (containsSingleton(beanName) || containsBeanDefinition(beanName)) {
// 3.name不带&前缀，或者是FactoryBean，则返回true
return (!BeanFactoryUtils.isFactoryDereference(name) || isFactoryBean(name));
}
// Not found -> check parent.
// 4.没有找到则检查parentBeanFactory
BeanFactory parentBeanFactory = getParentBeanFactory();
return (parentBeanFactory != null && parentBeanFactory.containsBean(originalBeanName(name)));
}
}
autowireByType
- 解析 autowireByType 的注入
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
protected void autowireByType(
String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) {
//获取的属性类型转换器
TypeConverter converter = getCustomTypeConverter();
if (converter == null) {
converter = bw;
}
//用来存放解析的要注入的属性名
Set<String> autowiredBeanNames = new LinkedHashSet<>(4);
//获取要注入的属性名称（非简单属性（8种原始类型、字符、URL等都是简单属性））
String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw);
for (String propertyName : propertyNames) {
try {
//获取指定属性名称的属性Descriptor(Descriptor用来记载属性的getter setter type等情况)
PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName);
// Don't try autowiring by type for type Object: never makes sense,
// even if it technically is a unsatisfied, non-simple property.
//不对Object类型的属性进行装配注入，技术上没法实现，并且没有意义
//即如果属性类型为 Object，则忽略，不做解析
if (Object.class != pd.getPropertyType()) {
// 获取指定属性的set方法，封装成MethodParameter（必须有set方法才能通过属性来注入）
MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd);
// Do not allow eager init for type matching in case of a prioritized post-processor.
// 对于继承了PriorityOrdered的post-processor，不允许立即初始化(热加载)
boolean eager = !(bw.getWrappedInstance() instanceof PriorityOrdered);
// 创建一个要被注入的依赖描述，方便提供统一的访问
// 将MethodParameter的方法参数索引信息封装成DependencyDescriptor
DependencyDescriptor desc = new AutowireByTypeDependencyDescriptor(methodParam, eager);
//根据容器的BeanDefinition解析依赖关系，返回所有要被注入的Bean实例
//解析当前属性所匹配的bean实例，并把解析到的bean实例的beanName存储在autowiredBeanNames中
Object autowiredArgument = resolveDependency(desc, beanName, autowiredBeanNames, converter);
if (autowiredArgument != null) {
// 将解析出的 bean 存入到属性值列表pvs中
pvs.add(propertyName, autowiredArgument);
}
for (String autowiredBeanName : autowiredBeanNames) {
// 注册依赖关系，beanName依赖autowiredBeanName
registerDependentBean(autowiredBeanName, beanName);
if (logger.isTraceEnabled()) {
logger.trace("Autowiring by type from bean name '" + beanName + "' via property '" +
propertyName + "' to bean named '" + autowiredBeanName + "'");
}
}
//清除已注入属性的记录
autowiredBeanNames.clear();
}
}
catch (BeansException ex) {
throw new UnsatisfiedDependencyException(mbd.getResourceDescription(), beanName, propertyName, ex);
}
}
}
}
-
寻找 bw 中需要依赖注入的属性。
-
解析当前属性所匹配的 bean 实例，并把解析到的 bean 实例的 beanName 存储在 autowiredBeanNames 中。
-
注册依赖关系，beanName 依赖 autowiredBeanName。
applyPropertyValues
- 最终将属性注入到Bean的Wrapper实例里，这里的注入主要是供显式配置了autowiredbyName或者ByType的属性注入。
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
if (pvs.isEmpty()) {
return;
}
if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) {
//设置安全上下文，JDK安全机制
((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
}
MutablePropertyValues mpvs = null;
List<PropertyValue> original;
// 1.获取属性值列表
if (pvs instanceof MutablePropertyValues) {
mpvs = (MutablePropertyValues) pvs;
// 1.1 如果mpvs中的值已经被转换为对应的类型，那么可以直接设置到BeanWrapper中
if (mpvs.isConverted()) {
// Shortcut: use the pre-converted values as-is.
try {
bw.setPropertyValues(mpvs);
return;
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}
original = mpvs.getPropertyValueList();
}
else {
// 1.2 如果pvs并不是使用MutablePropertyValues封装的类型，那么直接使用原始的属性获取方法
original = Arrays.asList(pvs.getPropertyValues());
}
TypeConverter converter = getCustomTypeConverter();
if (converter == null) {
converter = bw;
}
// 2.1 获取对应的解析器
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
// Create a deep copy, resolving any references for values.
// 2.2 创建深层拷贝副本，用于存放解析后的属性值
List<PropertyValue> deepCopy = new ArrayList<>(original.size());
boolean resolveNecessary = false;
// 3.遍历属性，将属性转换为对应类的对应属性的类型
for (PropertyValue pv : original) {
if (pv.isConverted()) {
// 3.1 如果pv已经包含转换的值，则直接添加到deepCopy
deepCopy.add(pv);
}
else {
// 3.2 否则，进行转换
// 3.2.1 拿到pv的原始属性名和属性值
String propertyName = pv.getName();
Object originalValue = pv.getValue();
if (originalValue == AutowiredPropertyMarker.INSTANCE) {
Method writeMethod = bw.getPropertyDescriptor(propertyName).getWriteMethod();
if (writeMethod == null) {
throw new IllegalArgumentException("Autowire marker for property without write method: " + pv);
}
originalValue = new DependencyDescriptor(new MethodParameter(writeMethod, 0), true);
}
// 3.2.2 使用解析器解析原始属性值
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
Object convertedValue = resolvedValue;
// 3.2.3 判断该属性是否可转换
boolean convertible = bw.isWritableProperty(propertyName) &&
!PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
if (convertible) {
// 3.2.4 如果可转换，则转换指定目标属性的给定值
convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
}
// Possibly store converted value in merged bean definition,
// in order to avoid re-conversion for every created bean instance.
// 3.2.5 在合并的BeanDefinition中存储转换后的值，以避免为每个创建的bean实例重新转换
if (resolvedValue == originalValue) {
if (convertible) {
pv.setConvertedValue(convertedValue);
}
deepCopy.add(pv);
}
else if (convertible && originalValue instanceof TypedStringValue &&
!((TypedStringValue) originalValue).isDynamic() &&
!(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) {
pv.setConvertedValue(convertedValue);
deepCopy.add(pv);
}
else {
resolveNecessary = true;
deepCopy.add(new PropertyValue(pv, convertedValue));
}
}
}
if (mpvs != null && !resolveNecessary) {
mpvs.setConverted();
}
// Set our (possibly massaged) deep copy.
try {
// 4.设置bean的属性值为deepCopy
bw.setPropertyValues(new MutablePropertyValues(deepCopy));
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}
}
initializeBean
对bean进行初始化
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
// 1.激活Aware方法
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareMethods(beanName, bean);
return null;
}, getAccessControlContext());
}
else {
invokeAwareMethods(beanName, bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
// 2.在初始化前应用BeanPostProcessor的postProcessBeforeInitialization方法，允许对bean实例进行包装
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
// 3.调用初始化方法
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()) {
// 4.在初始化后应用BeanPostProcessor的postProcessAfterInitialization方法，允许对bean实例进行包装
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
// 5.返回wrappedBean
return wrappedBean;
}
}
invokeAwareMethods
- 激活 Aware方法
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
private void invokeAwareMethods(final String beanName, final Object bean) {
if (bean instanceof Aware) {
// BeanNameAware: 实现此接口的类想要拿到beanName，因此我们在这边赋值给它
if (bean instanceof BeanNameAware) {
((BeanNameAware) bean).setBeanName(beanName);
}
// BeanClassLoaderAware：实现此接口的类想要拿到beanClassLoader，因此我们在这边赋值给它
if (bean instanceof BeanClassLoaderAware) {
ClassLoader bcl = getBeanClassLoader();
if (bcl != null) {
((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
}
}
// BeanFactoryAware: 实现此接口的类想要拿到 BeanFactory，因此我们在这边赋值给它
if (bean instanceof BeanFactoryAware) {
((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
}
}
}
}
如果对 Spring 比较熟悉的同学应该知道，以 Aware 为结尾的类都是一些扩展接口，用于提供给开发者获取到 BeanFactory 中的一些属性或对象。
applyBeanPostProcessorsBeforeInitialization
- 在初始化前应用后置处理器 BeanPostProcessor 的 postProcessBeforeInitialization 方法，允许对 bean 实例进行包装。
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
// 1.遍历所有注册的BeanPostProcessor实现类，调用postProcessBeforeInitialization方法
for (BeanPostProcessor processor : getBeanPostProcessors()) {
// 2.在bean初始化方法执行前，调用postProcessBeforeInitialization方法
Object current = processor.postProcessBeforeInitialization(result, beanName);
if (current == null) {
return result;
}
result = current;
}
return result;
}
}
postProcessBeforeInitialization
在 bean 初始化前，调用所有 BeanPostProcessors 的 postProcessBeforeInitialization 方法，这个在很早之前就说过了。这边提一个比较重要的实现类：ApplicationContextAwareProcessor。
class ApplicationContextAwareProcessor implements BeanPostProcessor {
private final ConfigurableApplicationContext applicationContext;
private final StringValueResolver embeddedValueResolver;
@Override
@Nullable
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if (!(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)){
return bean;
}
AccessControlContext acc = null;
if (System.getSecurityManager() != null) {
acc = this.applicationContext.getBeanFactory().getAccessControlContext();
}
if (acc != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareInterfaces(bean);
return null;
}, acc);
}
else {
// 调用Aware接口
invokeAwareInterfaces(bean);
}
return bean;
}
private void invokeAwareInterfaces(Object bean) {
if (bean instanceof EnvironmentAware) {
((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
}
if (bean instanceof EmbeddedValueResolverAware) {
((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
}
if (bean instanceof ResourceLoaderAware) {
((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
}
if (bean instanceof ApplicationEventPublisherAware) {
((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
}
if (bean instanceof MessageSourceAware) {
((MessageSourceAware) bean).setMessageSource(this.applicationContext);
}
// ApplicationContextAware：实现此接口的类想要拿到ApplicationContext，因此我们在这边赋值给它
if (bean instanceof ApplicationContextAware) {
((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
}
}
}
我们经常通过实现 ApplicationContextAware 接口来拿到 ApplicationContext，我们之所以能拿到 ApplicationContext，就是在这边被赋值的。
invokeInitMethods
- 调用初始化方法
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
protected void invokeInitMethods(String beanName, final Object bean, @Nullable RootBeanDefinition mbd)
throws Throwable {
//如果当前bean是 InitializingBean类型的&&afterPropertiesSet这个方法没有注册为外部管理的初始化方法
//就回调afterPropertiesSet方法
boolean isInitializingBean = (bean instanceof InitializingBean);
if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
if (logger.isTraceEnabled()) {
logger.trace("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
}
// 调用afterPropertiesSet方法
if (System.getSecurityManager() != null) {
try {
AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
((InitializingBean) bean).afterPropertiesSet();
return null;
}, getAccessControlContext());
}
catch (PrivilegedActionException pae) {
throw pae.getException();
}
}
else {
((InitializingBean) bean).afterPropertiesSet();
}
}
if (mbd != null && bean.getClass() != NullBean.class) {
String initMethodName = mbd.getInitMethodName();
//如果设置了initMethod方法的话也会执行用户配置的初始话方法
//并且这个类不是 InitializingBean类型和不是afterPropertiesSet方法 ；
//才能执行用户配置的方法
if (StringUtils.hasLength(initMethodName) &&
!(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
!mbd.isExternallyManagedInitMethod(initMethodName)) {
// 调用自定义初始化方法
invokeCustomInitMethod(beanName, bean, mbd);
}
}
}
}
invokeCustomInitMethod
- 调用自定义初始化方法
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
protected void invokeCustomInitMethod(String beanName, final Object bean, RootBeanDefinition mbd)
throws Throwable {
// 1.拿到初始化方法的方法名
String initMethodName = mbd.getInitMethodName();
Assert.state(initMethodName != null, "No init method set");
// 2.根据方法名拿到方法
Method initMethod = (mbd.isNonPublicAccessAllowed() ?
BeanUtils.findMethod(bean.getClass(), initMethodName) :
ClassUtils.getMethodIfAvailable(bean.getClass(), initMethodName));
if (initMethod == null) {
// 3.如果不存在initMethodName对应的方法，并且是强制执行初始化方法(默认为强制), 则抛出异常
if (mbd.isEnforceInitMethod()) {
throw new BeanDefinitionValidationException("Could not find an init method named '" +
initMethodName + "' on bean with name '" + beanName + "'");
}
else {
// 如果设置了非强制，找不到则直接返回
if (logger.isTraceEnabled()) {
logger.trace("No default init method named '" + initMethodName +
"' found on bean with name '" + beanName + "'");
}
// Ignore non-existent default lifecycle methods.
return;
}
}
if (logger.isTraceEnabled()) {
logger.trace("Invoking init method '" + initMethodName + "' on bean with name '" + beanName + "'");
}
Method methodToInvoke = ClassUtils.getInterfaceMethodIfPossible(initMethod);
// 4.调用初始化方法
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
ReflectionUtils.makeAccessible(methodToInvoke);
return null;
});
try {
AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () ->
methodToInvoke.invoke(bean), getAccessControlContext());
}
catch (PrivilegedActionException pae) {
InvocationTargetException ex = (InvocationTargetException) pae.getException();
throw ex.getTargetException();
}
}
else {
try {
ReflectionUtils.makeAccessible(methodToInvoke);
methodToInvoke.invoke(bean);
}
catch (InvocationTargetException ex) {
throw ex.getTargetException();
}
}
}
}
applyBeanPostProcessorsAfterInitialization
- 在初始化后应用BeanPostProcessor的postProcessAfterInitialization方法，允许对bean实例进行包装。
public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFactory
implements AutowireCapableBeanFactory {
@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
// 1.遍历所有注册的BeanPostProcessor实现类，调用postProcessAfterInitialization方法
for (BeanPostProcessor processor : getBeanPostProcessors()) {
// 2.在bean初始化后，调用postProcessAfterInitialization方法
Object current = processor.postProcessAfterInitialization(result, beanName);
if (current == null) {
// 3.如果返回null，则不会调用后续的BeanPostProcessors
return result;
}
result = current;
}
return result;
}
}
registerDisposableBeanIfNecessary
- 注册用于销毁的bean，执行销毁操作的有三种：自定义destroy方法、DisposableBean接口、DestructionAwareBeanPostProcessor。
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {
protected void registerDisposableBeanIfNecessary(String beanName, Object bean, RootBeanDefinition mbd) {
AccessControlContext acc = (System.getSecurityManager() != null ? getAccessControlContext() : null);
// 1.mbd的scope不是prototype && 给定的bean需要在关闭时销毁
if (!mbd.isPrototype() && requiresDestruction(bean, mbd)) {
if (mbd.isSingleton()) {
// Register a DisposableBean implementation that performs all destruction
// work for the given bean: DestructionAwareBeanPostProcessors,
// DisposableBean interface, custom destroy method.
// 2.单例模式下注册用于销毁的bean到disposableBeans缓存，执行给定bean的所有销毁工作：
// DestructionAwareBeanPostProcessors，DisposableBean接口，自定义销毁方法
// 2.1 DisposableBeanAdapter：使用DisposableBeanAdapter来封装用于销毁的bean
registerDisposableBean(beanName,
new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
}
else {
// 3.自定义scope处理
// A bean with a custom scope...
Scope scope = this.scopes.get(mbd.getScope());
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + mbd.getScope() + "'");
}
scope.registerDestructionCallback(beanName,
new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
}
}
}
}
requiresDestruction
- 判断给定的 bean 是否需要在关闭时销毁
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {
protected boolean requiresDestruction(Object bean, RootBeanDefinition mbd) {
// 1.DisposableBeanAdapter.hasDestroyMethod(bean, mbd)：判断bean是否有destroy方法
// 2.hasDestructionAwareBeanPostProcessors()：判断当前BeanFactory是否注册过DestructionAwareBeanPostProcessor
// 3.DisposableBeanAdapter.hasApplicableProcessors：是否存在适用于bean的DestructionAwareBeanPostProcessor
return (bean.getClass() != NullBean.class &&
(DisposableBeanAdapter.hasDestroyMethod(bean, mbd) || (hasDestructionAwareBeanPostProcessors() &&
DisposableBeanAdapter.hasApplicableProcessors(bean, getBeanPostProcessors()))));
}
}
hasDestroyMethod
- DisposableBeanAdapter.hasDestroyMethod(bean, mbd)：判断 bean 是否有 destroy 方法。
class DisposableBeanAdapter implements DisposableBean, Runnable, Serializable {
public static boolean hasDestroyMethod(Object bean, RootBeanDefinition beanDefinition) {
if (bean instanceof DisposableBean || bean instanceof AutoCloseable) {
// 1.如果bean实现了DisposableBean接口 或者 bean是AutoCloseable实例，则返回true
return true;
}
// 2.拿到bean自定义的destroy方法名
String destroyMethodName = beanDefinition.getDestroyMethodName();
if (AbstractBeanDefinition.INFER_METHOD.equals(destroyMethodName)) {
// 3.如果自定义的destroy方法名为“(inferred)”（该名字代表需要我们自己去推测destroy的方法名），
// 则检查该bean是否存在方法名为“close”或“shutdown”的方法，如果存在，则返回true
return (ClassUtils.hasMethod(bean.getClass(), CLOSE_METHOD_NAME) ||
ClassUtils.hasMethod(bean.getClass(), SHUTDOWN_METHOD_NAME));
}
// 4.如果destroyMethodName不为空，则返回true
return StringUtils.hasLength(destroyMethodName);
}
}
如果 bean 实现了 DisposableBean 接口或 bean 是 AutoCloseable 实例，则返回 true，因为这两个接口都有关闭的方法
hasApplicableProcessors
- DisposableBeanAdapter.hasApplicableProcessors：是否存在适用于 bean 的 DestructionAwareBeanPostProcessor。
class DisposableBeanAdapter implements DisposableBean, Runnable, Serializable {
public static boolean hasApplicableProcessors(Object bean, List<BeanPostProcessor> postProcessors) {
if (!CollectionUtils.isEmpty(postProcessors)) {
// 1.遍历所有的BeanPostProcessor
for (BeanPostProcessor processor : postProcessors) {
// 2.如果processor是DestructionAwareBeanPostProcessor
if (processor instanceof DestructionAwareBeanPostProcessor) {
DestructionAwareBeanPostProcessor dabpp = (DestructionAwareBeanPostProcessor) processor;
if (dabpp.requiresDestruction(bean)) {
// 3.如果给定的bean实例需要通过此后处理器进行销毁，则返回true
return true;
}
}
}
}
return false;
}
}
DisposableBeanAdapter
- 使用 DisposableBeanAdapter 来封装用于销毁的 bean。
class DisposableBeanAdapter implements DisposableBean, Runnable, Serializable {
public DisposableBeanAdapter(Object bean, String beanName, RootBeanDefinition beanDefinition,
List<BeanPostProcessor> postProcessors, @Nullable AccessControlContext acc) {
Assert.notNull(bean, "Disposable bean must not be null");
this.bean = bean;
this.beanName = beanName;
// 1.判断bean是否需要调用DisposableBean的destroy方法
this.invokeDisposableBean =
(this.bean instanceof DisposableBean && !beanDefinition.isExternallyManagedDestroyMethod("destroy"));
this.nonPublicAccessAllowed = beanDefinition.isNonPublicAccessAllowed();
this.acc = acc;
// 2.拿到自定义的destroy方法名
String destroyMethodName = inferDestroyMethodIfNecessary(bean, beanDefinition);
if (destroyMethodName != null && !(this.invokeDisposableBean && "destroy".equals(destroyMethodName)) &&
!beanDefinition.isExternallyManagedDestroyMethod(destroyMethodName)) {
this.destroyMethodName = destroyMethodName;
// 3.拿到自定义的destroy方法
Method destroyMethod = determineDestroyMethod(destroyMethodName);
if (destroyMethod == null) {
if (beanDefinition.isEnforceDestroyMethod()) {
// 4.如果destroy方法名为空，并且enforceDestroyMethod为true，则抛出异常
throw new BeanDefinitionValidationException("Could not find a destroy method named '" +
destroyMethodName + "' on bean with name '" + beanName + "'");
}
}
else {
// 5.拿到destroy方法的参数类型数组
Class<?>[] paramTypes = destroyMethod.getParameterTypes();
if (paramTypes.length > 1) {
// 6.如果destroy方法的参数大于1个，则抛出异常
throw new BeanDefinitionValidationException("Method '" + destroyMethodName + "' of bean '" +
beanName + "' has more than one parameter - not supported as destroy method");
}
else if (paramTypes.length == 1 && boolean.class != paramTypes[0]) {
// 7.如果destroy方法的参数为1个，并且该参数的类型不为boolean，则抛出异常
throw new BeanDefinitionValidationException("Method '" + destroyMethodName + "' of bean '" +
beanName + "' has a non-boolean parameter - not supported as destroy method");
}
destroyMethod = ClassUtils.getInterfaceMethodIfPossible(destroyMethod);
}
//赋值给this.destroyMethod
this.destroyMethod = destroyMethod;
}
// 8.查找DestructionAwareBeanPostProcessors，并赋值给this.beanPostProcessors
this.beanPostProcessors = filterPostProcessors(postProcessors, bean);
}
}
inferDestroyMethodIfNecessary
- 拿到自定义的 destroy 方法名。
class DisposableBeanAdapter implements DisposableBean, Runnable, Serializable {
@Nullable
private String inferDestroyMethodIfNecessary(Object bean, RootBeanDefinition beanDefinition) {
// 1.拿到beanDefinition的destroy方法名
String destroyMethodName = beanDefinition.getDestroyMethodName();
// 2.如果destroy方法名为“(inferred)”|| destroyMethodName为null，并且bean是AutoCloseable实例
if (AbstractBeanDefinition.INFER_METHOD.equals(destroyMethodName) ||
(destroyMethodName == null && bean instanceof AutoCloseable)) {
// Only perform destroy method inference or Closeable detection
// in case of the bean not explicitly implementing DisposableBean
// 3.如果bean没有实现DisposableBean接口，则尝试推测destroy方法的名字
if (!(bean instanceof DisposableBean)) {
try {
// 4.尝试在bean中寻找方法名为close的方法作为destroy方法
return bean.getClass().getMethod(CLOSE_METHOD_NAME).getName();
}
catch (NoSuchMethodException ex) {
try {
// 5.尝试在bean中寻找方法名为close的方法作为shutdown方法
return bean.getClass().getMethod(SHUTDOWN_METHOD_NAME).getName();
}
catch (NoSuchMethodException ex2) {
// no candidate destroy method found
}
}
}
// 6.如果没有找到，则返回null
return null;
}
return (StringUtils.hasLength(destroyMethodName) ? destroyMethodName : null);
}
}
filterPostProcessors
- 查找 DestructionAwareBeanPostProcessors，并赋值给 beanPostProcessors。
class DisposableBeanAdapter implements DisposableBean, Runnable, Serializable {
@Nullable
private List<DestructionAwareBeanPostProcessor> filterPostProcessors(List<BeanPostProcessor> processors, Object bean) {
List<DestructionAwareBeanPostProcessor> filteredPostProcessors = null;
if (!CollectionUtils.isEmpty(processors)) {
filteredPostProcessors = new ArrayList<>(processors.size());
// 1.遍历所有的BeanPostProcessor
for (BeanPostProcessor processor : processors) {
// 2.如果processor是DestructionAwareBeanPostProcessor
if (processor instanceof DestructionAwareBeanPostProcessor) {
DestructionAwareBeanPostProcessor dabpp = (DestructionAwareBeanPostProcessor) processor;
if (dabpp.requiresDestruction(bean)) {
// 3.如果给定的bean实例需要通过此后处理器进行销毁，则添加到filteredPostProcessors
filteredPostProcessors.add(dabpp);
}
}
}
}
return filteredPostProcessors;
}
}
总结
至此，finishBeanFactoryInitialization 方法解析完毕，在 finishBeanFactoryInitialization 方法中，我们主要做了以下操作：
- 将之前解析的 BeanDefinition 进一步处理，将有父 BeanDefinition 的进行合并，获得 MergedBeanDefinition
- 尝试从缓存获取 bean 实例
- 处理特殊的 bean —— FactoryBean 的创建
- 创建 bean 实例
- 循环引用的处理
- bean 实例属性填充
- bean 实例的初始化
- BeanPostProcessor 的各种扩展应用
finishBeanFactoryInitialization 方法解析的结束，也标志着 Spring IoC 整个构建过程中，重要的内容基本都已经解析完毕。
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