Spring源码之IoC容器的Bean创建和依赖注入，DefaultListableBeanFactory容器为例

接上篇Spring源码之IoC容器初始化过程，以FileSystemXmlApplicationContext容器为例
因为FileSystemXmlApplicationContext使用的容器为DefaultListableBeanFactory，所以该篇基于DefaultListableBeanFactory的实现分析依赖注入过程。

获取Bean的总体流程

getBean流程：
依赖注入通过BeanFactory的getBean方法触发。
DefaultListableBeanFactory的getBean方法通过继承AbstractAutowireCapableBeanFactory，AbstractAutowireCapableBeanFactory继承AbstractBeanFactory获得，具体的实现在AbstractBeanFactory中。

1、通过getBean方法触发依赖注入

2、getBean方法调用doGetBean方法，这是实际触发依赖注入的方法

3、先从缓存中取得Bean，处理那些已经被创建过的单件模式的Bean，对这种Bean的请求不需要重复的创建

4、如果从缓存中获得Bean，通过getObjectForBeanInstance方法完成FactoryBean的相关处理，取得FactoryBean的处理结果。

5、如果从缓存中未获得Bean，并且双亲BeanFactory不为null。检查当前IoC容器中是否存在对应的BeanDefinition，也就是检查是否能在当前的BeanFactory的Map中取得需要的Bean。

6、如果在当前的BeanFactory工厂中取不到BeanDefinition，则到双亲BeanFactory中取，也就是调用双亲BeanFactory的getBean方法。如果在当前的双亲工厂中还取不到，则递归顺着双亲BeanFactory链一直向上查找。

7、如果双亲BeanFactory为null，或者当前IoC容器中存在对应的BeanDefinition，根据Bean的名称获取BeanDefinition。

8、获取当前Bean的所有依赖的Bean名称，把依赖的Bean注册到dependentBeanMap中。并调用getBean方法注册每个依赖Bean的依赖Bean。调用getBean方法传入依赖Bean名称，这样会触发getBean的递归调用，直到取到一个没有任何依赖的Bean为止。

9、判断Bean是Singleton还是Prototype，通过调用createBean方法创建Bean实例，通过getObjectForBeanInstance方法完成FactoryBean的相关处理。

10、最后对Bean进行类型检查，如果没问题，则返回这个新创建的Bean，这个Bean是包含了依赖关系的Bean。

Bean对象的实例化

createBean方法流程：
该方法在AbstractAutowireCapableBeanFactory中实现

1、判断需要创建的Bean是否可以实例化，这个类是否可以通过类装载器来载入

2、如果Bean配置了PostProcessor，则获取一个proxy代理对象。

3、createBean调用doCreateBean创建Bean。doCreateBean中，用一个BeanWrapper持有创建出来的Bean对象。

4、如果是Singleton，先把缓存中的同名Bean清除。如果缓存找那个存在对应的Bean，则返回对应的Bean并作为即将获取的Bean，如果缓存中不存在，则调用createBeanInstance创建Bean对象。

5、调用populateBean方法对Bean进行初始化，以及依赖关系的注入。

createBeanInstance方法：

1、确认需要创建的Bean实例的类可以实例化。

2、如果instanceSupplier不为空，则通过instanceSupplier直接获取实例。

3、如果有工厂方法，则通过工厂方法对Bean进行实例化。

4、以上两种情况都不满足，则使用构造函数进行实例化。

5、通过构造函数后置处理器determineConstructorsFromBeanPostProcessors, 来选择使用哪个构造函数来实例化Bean。

6、如果构造函数后置处理器返回的构造函数为空，则用默认的构造函数对Bean进行实例化。通过instantiateBean(beanName, mbd)方法进行实例化。

instantiateBean方法：

1、使用默认的实例化策略对Bean进行实例化，默认的策略是使用CGLIB来对Bean进行实例化。

2、调用instantiate实例化Bean

SimpleInstantiationStrategy中的instantiate方法：

MethodOverrides的作用是在spring配置中存在lookup-mehtod和rreplace-method的，而这两个配置在加载xml的时候就会统一存放在BeanDefinition中的methodOverrides属性里

1、判断MethodOverrides是否为空，不为空时，使用CGLIB来实例化对象。

2、MethodOverrides为空时，取得指定的构造器或者生成对象的工厂方法来对Bean进行实例化，通过BeanUtils进行实例化，BeanUtils通过Constructor来实例化Bean，使用的是JVM的反射功能。

Bean对象依赖关系的注入

populateBean方法:

1、在创建Bean后，执行Bean的后置处理BeanPostProcessor

2、获取Bean的所有属性PropertyValues

3、开始进行依赖注入，先处理autowire的注入

4、根据Bean的名字或者类型，调用autowireByName或autowireByType方法，来完成Bean的autowire注入

5、调用applyPropertyValues对属性进行注入

6、applyPropertyValues中，通过BeanDefinitionValueResolver对BeanDefinition进行解析，applyPropertyValues方法调用了resolveValueIfNecessary方法，resolveValueIfNecessary方法调用了resolveReference方法，resolveValueIfNecessary包含了所有对注入类型的处理。

7、通过bw.setPropertyValues(new MutablePropertyValues(deepCopy));进行依赖注入

resolveReference方法：

1、根据RuntimeBeanReference判断每个PropertyValue，也就是依赖对象，是否在双亲IoC容器中

2、如果是在双亲IoC容器中，Bean的类型不为空，根据类型从双亲IoC容器中获取Bean，否则根据名字从双亲IoC容器中获取Bean

3、如果不在双亲IoC容器中，从当前容器获取Bean的实例和名字，调用当前容器的getBean获取

4、完成以上步骤后，已经为依赖注入准备好了条件，接下来就是真正注入的方法，在BeanWrapper的setPropertyValues中实现的，具体是在BeanWrapperImpl中实现的。

5、通过bw.setPropertyValues方法，遍历所有的PropertyValue，挨个进行设置

6、最终在BeanWrapperImpl中的setValue方法中，通过反射进行注入

总结：

在Bean的创建爱你和对象依赖注入的过程中，需要依据BeanDefinition中的信息来递归地完成依赖注入。从上面的几个递归过程中可以看到，这些递归都是以getBean为入口的。

一个递归是在上下文体系中查找需要的Bean和创建Bean的递归调用；另一个递归是在依赖注入时，通过递归调用容器的getBean方法，得到当前Bean的依赖Bean，同时也触发对依赖Bean的创建和注入。

在对Bean的属性进行依赖注入时，解析的过程也是一个递归的过程。这样，根据依赖关系，一层一层地完成Bean的创建和注入，直到最后完成当前Bean的创建。有了这个顶层Bean的创建和对它的属性依赖注入的完成，意味着和当前Bean相关的整个依赖链的注入也完成了。

源码

BeanFactory中定义了getBean方法，依赖注入正是通过getBean方法触发

public interface BeanFactory {String FACTORY_BEAN_PREFIX = "&";Object getBean(String var1) throws BeansException;<T> T getBean(String var1, Class<T> var2) throws BeansException;Object getBean(String var1, Object... var2) throws BeansException;<T> T getBean(Class<T> var1) throws BeansException;<T> T getBean(Class<T> var1, Object... var2) throws BeansException;<T> ObjectProvider<T> getBeanProvider(Class<T> var1);<T> ObjectProvider<T> getBeanProvider(ResolvableType var1);boolean containsBean(String var1);boolean isSingleton(String var1) throws NoSuchBeanDefinitionException;boolean isPrototype(String var1) throws NoSuchBeanDefinitionException;boolean isTypeMatch(String var1, ResolvableType var2) throws NoSuchBeanDefinitionException;boolean isTypeMatch(String var1, Class<?> var2) throws NoSuchBeanDefinitionException;@NullableClass<?> getType(String var1) throws NoSuchBeanDefinitionException;@NullableClass<?> getType(String var1, boolean var2) throws NoSuchBeanDefinitionException;String[] getAliases(String var1);
}

doGetBean方法源码

    protected <T> T doGetBean(String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly) throws BeansException {String beanName = this.transformedBeanName(name);// 先从缓存中取得Bean，处理那些已经被创建过的单件模式的Bean，对这种Bean的请求不需要重复的创建Object sharedInstance = this.getSingleton(beanName);Object bean;if (sharedInstance != null && args == null) {if (this.logger.isTraceEnabled()) {if (this.isSingletonCurrentlyInCreation(beanName)) {this.logger.trace("Returning eagerly cached instance of singleton bean '" + beanName + "' that is not fully initialized yet - a consequence of a circular reference");} else {this.logger.trace("Returning cached instance of singleton bean '" + beanName + "'");}}// 如果从缓存中获得Bean，通过getObjectForBeanInstance方法完成FactoryBean的相关处理，// 取得FactoryBean的处理结果。bean = this.getObjectForBeanInstance(sharedInstance, name, beanName, (RootBeanDefinition)null);} else {if (this.isPrototypeCurrentlyInCreation(beanName)) {throw new BeanCurrentlyInCreationException(beanName);}// 如果从缓存中未获得Bean，并且双亲BeanFactory不为null。// 检查当前IoC容器中是否存在对应的BeanDefinition，也就是检查是否能在当前的BeanFactory的Map中取得需要的Bean。BeanFactory parentBeanFactory = this.getParentBeanFactory();if (parentBeanFactory != null && !this.containsBeanDefinition(beanName)) {// 如果在当前的BeanFactory工厂中取不到BeanDefinition，则到双亲BeanFactory中取，// 也就是调用双亲BeanFactory的getBean方法。如果在当前的双亲工厂中还取不到，// 则递归顺着双亲BeanFactory链一直向上查找。String nameToLookup = this.originalBeanName(name);if (parentBeanFactory instanceof AbstractBeanFactory) {return ((AbstractBeanFactory)parentBeanFactory).doGetBean(nameToLookup, requiredType, args, typeCheckOnly);}if (args != null) {return parentBeanFactory.getBean(nameToLookup, args);}if (requiredType != null) {return parentBeanFactory.getBean(nameToLookup, requiredType);}return parentBeanFactory.getBean(nameToLookup);}if (!typeCheckOnly) {this.markBeanAsCreated(beanName);}// 如果双亲BeanFactory为null，或者当前IoC容器中存在对应的BeanDefinition，// 根据Bean的名称获取BeanDefinition。try {RootBeanDefinition mbd = this.getMergedLocalBeanDefinition(beanName);this.checkMergedBeanDefinition(mbd, beanName, args);String[] dependsOn = mbd.getDependsOn();String[] var11;if (dependsOn != null) {var11 = dependsOn;int var12 = dependsOn.length;// 获取当前Bean的所有依赖的Bean名称，把依赖的Bean注册到dependentBeanMap中。// 并调用getBean方法注册每个依赖Bean的依赖Bean。for(int var13 = 0; var13 < var12; ++var13) {String dep = var11[var13];if (this.isDependent(beanName, dep)) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");}this.registerDependentBean(dep, beanName);try {this.getBean(dep);} catch (NoSuchBeanDefinitionException var24) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "'" + beanName + "' depends on missing bean '" + dep + "'", var24);}}}// 判断Bean是Singleton还是Prototype，通过调用createBean方法创建Bean实例，// 通过getObjectForBeanInstance方法完成FactoryBean的相关处理。if (mbd.isSingleton()) {sharedInstance = this.getSingleton(beanName, () -> {try {return this.createBean(beanName, mbd, args);} catch (BeansException var5) {this.destroySingleton(beanName);throw var5;}});bean = this.getObjectForBeanInstance(sharedInstance, name, beanName, mbd);} else if (mbd.isPrototype()) {var11 = null;Object prototypeInstance;try {this.beforePrototypeCreation(beanName);prototypeInstance = this.createBean(beanName, mbd, args);} finally {this.afterPrototypeCreation(beanName);}bean = this.getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);} else {String scopeName = mbd.getScope();if (!StringUtils.hasLength(scopeName)) {throw new IllegalStateException("No scope name defined for bean ��" + beanName + "'");}Scope 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, () -> {this.beforePrototypeCreation(beanName);Object var4;try {var4 = this.createBean(beanName, mbd, args);} finally {this.afterPrototypeCreation(beanName);}return var4;});bean = this.getObjectForBeanInstance(scopedInstance, name, beanName, mbd);} catch (IllegalStateException var23) {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", var23);}}} catch (BeansException var26) {this.cleanupAfterBeanCreationFailure(beanName);throw var26;}}// 最后对Bean进行类型检查，如果没问题，// 则返回这个新创建的Bean，这个Bean是包含了依赖关系的Bean。if (requiredType != null && !requiredType.isInstance(bean)) {try {T convertedBean = this.getTypeConverter().convertIfNecessary(bean, requiredType);if (convertedBean == null) {throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());} else {return convertedBean;}} catch (TypeMismatchException var25) {if (this.logger.isTraceEnabled()) {this.logger.trace("Failed to convert bean '" + name + "' to required type '" + ClassUtils.getQualifiedName(requiredType) + "'", var25);}throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());}} else {return bean;}}

createBean方法

    protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException {if (this.logger.isTraceEnabled()) {this.logger.trace("Creating instance of bean '" + beanName + "'");}RootBeanDefinition mbdToUse = mbd;Class<?> resolvedClass = this.resolveBeanClass(mbd, beanName, new Class[0]);if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {mbdToUse = new RootBeanDefinition(mbd);mbdToUse.setBeanClass(resolvedClass);}try {mbdToUse.prepareMethodOverrides();} catch (BeanDefinitionValidationException var9) {throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(), beanName, "Validation of method overrides failed", var9);}Object beanInstance;try {beanInstance = this.resolveBeforeInstantiation(beanName, mbdToUse);if (beanInstance != null) {return beanInstance;}} catch (Throwable var10) {throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName, "BeanPostProcessor before instantiation of bean failed", var10);}try {beanInstance = this.doCreateBean(beanName, mbdToUse, args);if (this.logger.isTraceEnabled()) {this.logger.trace("Finished creating instance of bean '" + beanName + "'");}return beanInstance;} catch (ImplicitlyAppearedSingletonException | BeanCreationException var7) {throw var7;} catch (Throwable var8) {throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", var8);}}

doCreateBean方法

    protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException {BeanWrapper instanceWrapper = null;if (mbd.isSingleton()) {instanceWrapper = (BeanWrapper)this.factoryBeanInstanceCache.remove(beanName);}if (instanceWrapper == null) {instanceWrapper = this.createBeanInstance(beanName, mbd, args);}Object bean = instanceWrapper.getWrappedInstance();Class<?> beanType = instanceWrapper.getWrappedClass();if (beanType != NullBean.class) {mbd.resolvedTargetType = beanType;}synchronized(mbd.postProcessingLock) {if (!mbd.postProcessed) {try {this.applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);} catch (Throwable var17) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Post-processing of merged bean definition failed", var17);}mbd.postProcessed = true;}}boolean earlySingletonExposure = mbd.isSingleton() && this.allowCircularReferences && this.isSingletonCurrentlyInCreation(beanName);if (earlySingletonExposure) {if (this.logger.isTraceEnabled()) {this.logger.trace("Eagerly caching bean '" + beanName + "' to allow for resolving potential circular references");}this.addSingletonFactory(beanName, () -> {return this.getEarlyBeanReference(beanName, mbd, bean);});}Object exposedObject = bean;try {this.populateBean(beanName, mbd, instanceWrapper);exposedObject = this.initializeBean(beanName, exposedObject, mbd);} catch (Throwable var18) {if (var18 instanceof BeanCreationException && beanName.equals(((BeanCreationException)var18).getBeanName())) {throw (BeanCreationException)var18;}throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Initialization of bean failed", var18);}if (earlySingletonExposure) {Object earlySingletonReference = this.getSingleton(beanName, false);if (earlySingletonReference != null) {if (exposedObject == bean) {exposedObject = earlySingletonReference;} else if (!this.allowRawInjectionDespiteWrapping && this.hasDependentBean(beanName)) {String[] dependentBeans = this.getDependentBeans(beanName);Set<String> actualDependentBeans = new LinkedHashSet(dependentBeans.length);String[] var12 = dependentBeans;int var13 = dependentBeans.length;for(int var14 = 0; var14 < var13; ++var14) {String dependentBean = var12[var14];if (!this.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 'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example.");}}}}try {this.registerDisposableBeanIfNecessary(beanName, bean, mbd);return exposedObject;} catch (BeanDefinitionValidationException var16) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Invalid destruction signature", var16);}}

createBeanInstance方法创建对象

    protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {Class<?> beanClass = this.resolveBeanClass(mbd, beanName, new Class[0]);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());} else {Supplier<?> instanceSupplier = mbd.getInstanceSupplier();if (instanceSupplier != null) {return this.obtainFromSupplier(instanceSupplier, beanName);} else if (mbd.getFactoryMethodName() != null) {return this.instantiateUsingFactoryMethod(beanName, mbd, args);} else {boolean resolved = false;boolean autowireNecessary = false;if (args == null) {synchronized(mbd.constructorArgumentLock) {if (mbd.resolvedConstructorOrFactoryMethod != null) {resolved = true;autowireNecessary = mbd.constructorArgumentsResolved;}}}if (resolved) {return autowireNecessary ? this.autowireConstructor(beanName, mbd, (Constructor[])null, (Object[])null) : this.instantiateBean(beanName, mbd);} else {Constructor<?>[] ctors = this.determineConstructorsFromBeanPostProcessors(beanClass, beanName);if (ctors == null && mbd.getResolvedAutowireMode() != 3 && !mbd.hasConstructorArgumentValues() && ObjectUtils.isEmpty(args)) {ctors = mbd.getPreferredConstructors();return ctors != null ? this.autowireConstructor(beanName, mbd, ctors, (Object[])null) : this.instantiateBean(beanName, mbd);} else {return this.autowireConstructor(beanName, mbd, ctors, args);}}}}}

instantiateBean方法

    protected BeanWrapper instantiateBean(String beanName, RootBeanDefinition mbd) {try {Object beanInstance;if (System.getSecurityManager() != null) {beanInstance = AccessController.doPrivileged(() -> {return this.getInstantiationStrategy().instantiate(mbd, beanName, this);}, this.getAccessControlContext());} else {beanInstance = this.getInstantiationStrategy().instantiate(mbd, beanName, this);}BeanWrapper bw = new BeanWrapperImpl(beanInstance);this.initBeanWrapper(bw);return bw;} catch (Throwable var5) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Instantiation of bean failed", var5);}}

通过反射创建对象

BeanUtils.instantiateClass(constructorToUse, new Object[0])

    public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException {Assert.notNull(ctor, "Constructor must not be null");try {ReflectionUtils.makeAccessible(ctor);if (KotlinDetector.isKotlinReflectPresent() && KotlinDetector.isKotlinType(ctor.getDeclaringClass())) {return BeanUtils.KotlinDelegate.instantiateClass(ctor, args);} else {Class<?>[] parameterTypes = ctor.getParameterTypes();Assert.isTrue(args.length <= parameterTypes.length, "Can't specify more arguments than constructor parameters");Object[] argsWithDefaultValues = new Object[args.length];for(int i = 0; i < args.length; ++i) {if (args[i] == null) {Class<?> parameterType = parameterTypes[i];argsWithDefaultValues[i] = parameterType.isPrimitive() ? DEFAULT_TYPE_VALUES.get(parameterType) : null;} else {argsWithDefaultValues[i] = args[i];}}return ctor.newInstance(argsWithDefaultValues);}} catch (InstantiationException var6) {throw new BeanInstantiationException(ctor, "Is it an abstract class?", var6);} catch (IllegalAccessException var7) {throw new BeanInstantiationException(ctor, "Is the constructor accessible?", var7);} catch (IllegalArgumentException var8) {throw new BeanInstantiationException(ctor, "Illegal arguments for constructor", var8);} catch (InvocationTargetException var9) {throw new BeanInstantiationException(ctor, "Constructor threw exception", var9.getTargetException());}}

通过CGLIB创建对象

this.instantiateWithMethodInjection(bd, beanName, owner)

    protected Object instantiateWithMethodInjection(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {return this.instantiateWithMethodInjection(bd, beanName, owner, (Constructor)null);}protected Object instantiateWithMethodInjection(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner, @Nullable Constructor<?> ctor, Object... args) {return (new CglibSubclassingInstantiationStrategy.CglibSubclassCreator(bd, owner)).instantiate(ctor, args);}

        public Object instantiate(@Nullable Constructor<?> ctor, Object... args) {Class<?> subclass = this.createEnhancedSubclass(this.beanDefinition);Object instance;if (ctor == null) {instance = BeanUtils.instantiateClass(subclass);} else {try {Constructor<?> enhancedSubclassConstructor = subclass.getConstructor(ctor.getParameterTypes());instance = enhancedSubclassConstructor.newInstance(args);} catch (Exception var6) {throw new BeanInstantiationException(this.beanDefinition.getBeanClass(), "Failed to invoke constructor for CGLIB enhanced subclass [" + subclass.getName() + "]", var6);}}Factory factory = (Factory)instance;factory.setCallbacks(new Callback[]{NoOp.INSTANCE, new CglibSubclassingInstantiationStrategy.LookupOverrideMethodInterceptor(this.beanDefinition, this.owner), new CglibSubclassingInstantiationStrategy.ReplaceOverrideMethodInterceptor(this.beanDefinition, this.owner)});return instance;}

createEnhancedSubclass方法

        private Class<?> createEnhancedSubclass(RootBeanDefinition beanDefinition) {Enhancer enhancer = new Enhancer();enhancer.setSuperclass(beanDefinition.getBeanClass());enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);if (this.owner instanceof ConfigurableBeanFactory) {ClassLoader cl = ((ConfigurableBeanFactory)this.owner).getBeanClassLoader();enhancer.setStrategy(new ClassLoaderAwareGeneratorStrategy(cl));}enhancer.setCallbackFilter(new CglibSubclassingInstantiationStrategy.MethodOverrideCallbackFilter(beanDefinition));enhancer.setCallbackTypes(CALLBACK_TYPES);return enhancer.createClass();}

populateBean方法设置依赖关系

populateBean方法

    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 {if (!mbd.isSynthetic() && this.hasInstantiationAwareBeanPostProcessors()) {Iterator var4 = this.getBeanPostProcessors().iterator();while(var4.hasNext()) {BeanPostProcessor bp = (BeanPostProcessor)var4.next();if (bp instanceof InstantiationAwareBeanPostProcessor) {InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor)bp;if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {return;}}}}PropertyValues pvs = mbd.hasPropertyValues() ? mbd.getPropertyValues() : null;int resolvedAutowireMode = mbd.getResolvedAutowireMode();if (resolvedAutowireMode == 1 || resolvedAutowireMode == 2) {MutablePropertyValues newPvs = new MutablePropertyValues((PropertyValues)pvs);if (resolvedAutowireMode == 1) {this.autowireByName(beanName, mbd, bw, newPvs);}if (resolvedAutowireMode == 2) {this.autowireByType(beanName, mbd, bw, newPvs);}pvs = newPvs;}boolean hasInstAwareBpps = this.hasInstantiationAwareBeanPostProcessors();boolean needsDepCheck = mbd.getDependencyCheck() != 0;PropertyDescriptor[] filteredPds = null;if (hasInstAwareBpps) {if (pvs == null) {pvs = mbd.getPropertyValues();}Iterator var9 = this.getBeanPostProcessors().iterator();while(var9.hasNext()) {BeanPostProcessor bp = (BeanPostProcessor)var9.next();if (bp instanceof InstantiationAwareBeanPostProcessor) {InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor)bp;PropertyValues pvsToUse = ibp.postProcessProperties((PropertyValues)pvs, bw.getWrappedInstance(), beanName);if (pvsToUse == null) {if (filteredPds == null) {filteredPds = this.filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);}pvsToUse = ibp.postProcessPropertyValues((PropertyValues)pvs, filteredPds, bw.getWrappedInstance(), beanName);if (pvsToUse == null) {return;}}pvs = pvsToUse;}}}if (needsDepCheck) {if (filteredPds == null) {filteredPds = this.filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);}this.checkDependencies(beanName, mbd, filteredPds, (PropertyValues)pvs);}if (pvs != null) {this.applyPropertyValues(beanName, mbd, bw, (PropertyValues)pvs);}}}

applyPropertyValues方法

    protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {if (!pvs.isEmpty()) {if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) {((BeanWrapperImpl)bw).setSecurityContext(this.getAccessControlContext());}MutablePropertyValues mpvs = null;List original;if (pvs instanceof MutablePropertyValues) {mpvs = (MutablePropertyValues)pvs;if (mpvs.isConverted()) {try {bw.setPropertyValues(mpvs);return;} catch (BeansException var18) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Error setting property values", var18);}}original = mpvs.getPropertyValueList();} else {original = Arrays.asList(pvs.getPropertyValues());}TypeConverter converter = this.getCustomTypeConverter();if (converter == null) {converter = bw;}BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, (TypeConverter)converter);List<PropertyValue> deepCopy = new ArrayList(original.size());boolean resolveNecessary = false;Iterator var11 = original.iterator();while(true) {while(var11.hasNext()) {PropertyValue pv = (PropertyValue)var11.next();if (pv.isConverted()) {deepCopy.add(pv);} else {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);}Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);Object convertedValue = resolvedValue;boolean convertible = bw.isWritableProperty(propertyName) && !PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);if (convertible) {convertedValue = this.convertForProperty(resolvedValue, propertyName, bw, (TypeConverter)converter);}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();}try {bw.setPropertyValues(new MutablePropertyValues(deepCopy));return;} catch (BeansException var19) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Error setting property values", var19);}}}}

resolveValueIfNecessary方法

    public Object resolveValueIfNecessary(Object argName, @Nullable Object value) {if (value instanceof RuntimeBeanReference) {RuntimeBeanReference ref = (RuntimeBeanReference)value;return this.resolveReference(argName, ref);} else if (value instanceof RuntimeBeanNameReference) {String refName = ((RuntimeBeanNameReference)value).getBeanName();refName = String.valueOf(this.doEvaluate(refName));if (!this.beanFactory.containsBean(refName)) {throw new BeanDefinitionStoreException("Invalid bean name '" + refName + "' in bean reference for " + argName);} else {return refName;}} else if (value instanceof BeanDefinitionHolder) {BeanDefinitionHolder bdHolder = (BeanDefinitionHolder)value;return this.resolveInnerBean(argName, bdHolder.getBeanName(), bdHolder.getBeanDefinition());} else if (value instanceof BeanDefinition) {BeanDefinition bd = (BeanDefinition)value;String innerBeanName = "(inner bean)#" + ObjectUtils.getIdentityHexString(bd);return this.resolveInnerBean(argName, innerBeanName, bd);} else {Object valueObject;if (value instanceof DependencyDescriptor) {Set<String> autowiredBeanNames = new LinkedHashSet(4);valueObject = this.beanFactory.resolveDependency((DependencyDescriptor)value, this.beanName, autowiredBeanNames, this.typeConverter);Iterator var19 = autowiredBeanNames.iterator();while(var19.hasNext()) {String autowiredBeanName = (String)var19.next();if (this.beanFactory.containsBean(autowiredBeanName)) {this.beanFactory.registerDependentBean(autowiredBeanName, this.beanName);}}return valueObject;} else if (value instanceof ManagedArray) {ManagedArray array = (ManagedArray)value;Class<?> elementType = array.resolvedElementType;if (elementType == null) {String elementTypeName = array.getElementTypeName();if (StringUtils.hasText(elementTypeName)) {try {elementType = ClassUtils.forName(elementTypeName, this.beanFactory.getBeanClassLoader());array.resolvedElementType = elementType;} catch (Throwable var7) {throw new BeanCreationException(this.beanDefinition.getResourceDescription(), this.beanName, "Error resolving array type for " + argName, var7);}} else {elementType = Object.class;}}return this.resolveManagedArray(argName, (List)value, elementType);} else if (value instanceof ManagedList) {return this.resolveManagedList(argName, (List)value);} else if (value instanceof ManagedSet) {return this.resolveManagedSet(argName, (Set)value);} else if (value instanceof ManagedMap) {return this.resolveManagedMap(argName, (Map)value);} else if (value instanceof ManagedProperties) {Properties original = (Properties)value;Properties copy = new Properties();original.forEach((propKey, propValue) -> {if (propKey instanceof TypedStringValue) {propKey = this.evaluate((TypedStringValue)propKey);}if (propValue instanceof TypedStringValue) {propValue = this.evaluate((TypedStringValue)propValue);}if (propKey != null && propValue != null) {copy.put(propKey, propValue);} else {throw new BeanCreationException(this.beanDefinition.getResourceDescription(), this.beanName, "Error converting Properties key/value pair for " + argName + ": resolved to null");}});return copy;} else if (value instanceof TypedStringValue) {TypedStringValue typedStringValue = (TypedStringValue)value;valueObject = this.evaluate(typedStringValue);try {Class<?> resolvedTargetType = this.resolveTargetType(typedStringValue);return resolvedTargetType != null ? this.typeConverter.convertIfNecessary(valueObject, resolvedTargetType) : valueObject;} catch (Throwable var8) {throw new BeanCreationException(this.beanDefinition.getResourceDescription(), this.beanName, "Error converting typed String value for " + argName, var8);}} else {return value instanceof NullBean ? null : this.evaluate(value);}}}

resolveReference方法

applyPropertyValues方法调用了resolveValueIfNecessary方法，resolveValueIfNecessary方法调用了resolveReference方法

    private Object resolveReference(Object argName, RuntimeBeanReference ref) {try {Class<?> beanType = ref.getBeanType();Object bean;if (ref.isToParent()) {BeanFactory parent = this.beanFactory.getParentBeanFactory();if (parent == null) {throw new BeanCreationException(this.beanDefinition.getResourceDescription(), this.beanName, "Cannot resolve reference to bean " + ref + " in parent factory: no parent factory available");}if (beanType != null) {bean = parent.getBean(beanType);} else {bean = parent.getBean(String.valueOf(this.doEvaluate(ref.getBeanName())));}} else {String resolvedName;if (beanType != null) {NamedBeanHolder<?> namedBean = this.beanFactory.resolveNamedBean(beanType);bean = namedBean.getBeanInstance();resolvedName = namedBean.getBeanName();} else {resolvedName = String.valueOf(this.doEvaluate(ref.getBeanName()));bean = this.beanFactory.getBean(resolvedName);}this.beanFactory.registerDependentBean(resolvedName, this.beanName);}if (bean instanceof NullBean) {bean = null;}return bean;} catch (BeansException var7) {throw new BeanCreationException(this.beanDefinition.getResourceDescription(), this.beanName, "Cannot resolve reference to bean '" + ref.getBeanName() + "' while setting " + argName, var7);}}