Spring IOC 源码解析（二）

Spring IOC 源码解析（二）

 

 

1、简介

       本篇文章是 SpringIOC源码解析（一）的续集，上一篇文章介绍了使用XML的方式启动Spring，然后追踪了BeanFactory容器的创建、配置文件的解析、BeanDefinition的注册等， 本篇文章继续分析Bean的初始化流程。

2、finishBeanFactoryInitialization(beanFactory); 
这个方法就是负责初始化所有的没有设置懒加载的 singleton bean

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
      // Initialize conversion service for this context.
      if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
            beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
         beanFactory.setConversionService(
               beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
      }

      // Register a default embedded value resolver if no bean post-processor
      // (such as a PropertyPlaceholderConfigurer bean) registered any before:
      // at this point, primarily for resolution in annotation attribute values.
      if (!beanFactory.hasEmbeddedValueResolver()) {
         beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
      }

       // 先初始化 LoadTimeWeaverAware 类型的 Bean
      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
      beanFactory.setTempClassLoader(null);

      // 冻结所有的bean定义，即已注册的bean定义将不会被修改或后处理
      beanFactory.freezeConfiguration();

      // 初始化, 继续往下看
      beanFactory.preInstantiateSingletons();
   }

conversionService
这种类型的bean最实用的场景就是用来将前端传过来的参数和后端的controller方法上的参数格式转换的时候使用
例如：前端要传一个String，后端使用Date接受的时候就可以这样操作

public class StringToDateConverter implements Converter<String, Date> {

    @Override
    public Date convert(String date) {
        try {
            return dateFormat.parse(date);
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("日期转换失败!");
            return null;
        }
        
    }
}

再搞个bean

<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
    <property name="converters">
        <list>
          <bean class="com.dw.study.convert.StringToDateConverter"/>
        </list>
    </property>
</bean>

EmbeddedValueResolver
利用EmbeddedValueResolver可以很方便的实现读取配置文件的属性

@Component
public class PropertiesUtil implements EmbeddedValueResolverAware {

    private StringValueResolver resolver;

    @Override
    public void setEmbeddedValueResolver(StringValueResolver resolver) {
        this.resolver = resolver;
    }
    
    /**
     * 获取属性时直接传入属性名称即可
     */
    public String getPropertiesValue(String key) {
        StringBuilder name = new StringBuilder("${").append(key).append("}");
        return resolver.resolveStringValue(name.toString());
    }
}

初始化
这里分析`beanFactory.preInstantiateSingletons()`方法

public void preInstantiateSingletons() throws BeansException {
        if (this.logger.isDebugEnabled()) {
            this.logger.debug("Pre-instantiating singletons in " + this);
        }
        // this.beanDefinitionNames 保存了所有的 beanNames
        List<String> beanNames = new ArrayList<String>(this.beanDefinitionNames);

        for (String beanName : beanNames) {

            // 合并父 Bean 中的配置，主意<bean id="" class="" parent="" /> 中的 parent属性
            RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);

            // 实例化不是抽象类、是单例的且不是懒加载的bean
            if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
                // 处理 FactoryBean
                if (isFactoryBean(beanName)) {
                    //在 beanName 前面加上“&” 符号
                    final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
                    // 判断当前 FactoryBean 是否是 SmartFactoryBean 的实现
                    boolean isEagerInit;
                    if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
                        isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
                            @Override
                            public Boolean run() {
                                return ((SmartFactoryBean<?>) factory).isEagerInit();
                            }
                        }, getAccessControlContext());
                    }
                    else {
                        isEagerInit = (factory instanceof SmartFactoryBean &&
                                ((SmartFactoryBean<?>) factory).isEagerInit());
                    }
                    if (isEagerInit) {

                        getBean(beanName);
                    }
                }
                else {
                    // 不是FactoryBean的直接使用此方法进行初始化
                    getBean(beanName);
                }
            }
        }
        // 如果bean实现了 SmartInitializingSingleton 接口的，那么在这里得到回调
        for (String beanName : beanNames) {
            Object singletonInstance = getSingleton(beanName);
            if (singletonInstance instanceof SmartInitializingSingleton) {
                final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
                if (System.getSecurityManager() != null) {
                    AccessController.doPrivileged(new PrivilegedAction<Object>() {
                        @Override
                        public Object run() {
                            smartSingleton.afterSingletonsInstantiated();
                            return null;
                        }
                    }, getAccessControlContext());
                }
                else {
                    smartSingleton.afterSingletonsInstantiated();
                }
            }
        }
    }

可以看到，不管是不是FactoryBean，最后都调用了`getBean(beanName)`，继续看这个方法吧

@Override
public Object getBean(String name) throws BeansException {
   return doGetBean(name, null, null, false);
}

  protected <T> T doGetBean(final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException {
        // 获取beanName，处理两种情况，一个是前面说的 FactoryBean(前面带 ‘&’)，再一个这个方法是可以根据别名来获取Bean的，所以在这里是要转换成最正统的BeanName
        // 主要逻辑就是如果是FactoryBean就把&去掉如果是别名就把根据别名获取真实名称后面就不贴代码了
        final String beanName = transformedBeanName(name);

        // 最后的返回值
        Object bean;

        // 检查是否已初始化
        Object sharedInstance = getSingleton(beanName);
        //如果已经初始化过了，且没有传args参数就代表是get，直接取出返回
        if (sharedInstance != null && args == null) {
            if (logger.isDebugEnabled()) {
                if (isSingletonCurrentlyInCreation(beanName)) {
                    logger.debug("...");
                }
                else {
                    logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
                }
            }
            // 这里如果是普通Bean 的话，直接返回，如果是 FactoryBean 的话，返回它创建的那个实例对象
            bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
        }

        else {
            // 如果存在prototype类型的这个bean
            if (isPrototypeCurrentlyInCreation(beanName)) {
                throw new BeanCurrentlyInCreationException(beanName);
            }

            // 如果当前BeanDefinition不存在这个bean且具有父BeanFactory
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                String nameToLookup = originalBeanName(name);
                // 返回父容器的查询结果
                if (args != null) {
                    return (T) parentBeanFactory.getBean(nameToLookup, args);
                }
                else {
                    return parentBeanFactory.getBean(nameToLookup, requiredType);
                }
            }

            if (!typeCheckOnly) {
                // typeCheckOnly 为 false，将当前 beanName 放入一个 alreadyCreated 的 Set 集合中。
                markBeanAsCreated(beanName);
            }

            /*
             * 到这就要创建bean了
             */
            try {
                final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
                checkMergedBeanDefinition(mbd, beanName, args);

                // 先初始化依赖的所有 Bean， depends-on 中定义的依赖
                String[] dependsOn = mbd.getDependsOn();
                if (dependsOn != null) {
                    for (String dep : dependsOn) {
                        // 检查是不是有循环依赖
                        if (isDependent(beanName, dep)) {
                            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                                    "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
                        }
                        // 注册一下依赖关系
                        registerDependentBean(dep, beanName);
                        // 先初始化被依赖项
                        getBean(dep);
                    }
                }

                // 如果是单例的
                if (mbd.isSingleton()) {
                    sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
                        @Override
                        public Object getObject() throws BeansException {
                            try {
                                // 执行创建 Bean，下面说
                                return createBean(beanName, mbd, args);
                            }
                            catch (BeansException ex) {
                                destroySingleton(beanName);
                                throw ex;
                            }
                        }
                    });
                    bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
                }

                // 如果是prototype
                else if (mbd.isPrototype()) {
                    Object prototypeInstance = null;
                    try {
                        beforePrototypeCreation(beanName);
                        // 执行创建 Bean
                        prototypeInstance = createBean(beanName, mbd, args);
                    }
                    finally {
                        afterPrototypeCreation(beanName);
                    }
                    bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
                }

                // 如果不是 singleton 和 prototype 那么就是自定义的scope、例如Web项目中的session等类型，这里就交给自定义scope的应用方去实现
                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, new ObjectFactory<Object>() {
                            @Override
                            public Object getObject() throws BeansException {
                                beforePrototypeCreation(beanName);
                                try {
                                    // 执行创建 Bean
                                    return createBean(beanName, mbd, args);
                                }
                                finally {
                                    afterPrototypeCreation(beanName);
                                }
                            }
                        });
                        bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
                    }
                    catch (IllegalStateException ex) {
                        throw new BeanCreationException(beanName,
                                "Scope '" + scopeName + "' is not active for the current thread; consider " +
                                        "defining a scoped proxy for this bean if you intend to refer to it from a singleton",
                                ex);
                    }
                }
            }
            catch (BeansException ex) {
                cleanupAfterBeanCreationFailure(beanName);
                throw ex;
            }
        }
        // bean的类型转换
        if (requiredType != null && bean != null && !requiredType.isInstance(bean)) {
            try {
                return getTypeConverter().convertIfNecessary(bean, requiredType);
            }catch (TypeMismatchException ex) {
            if (logger.isDebugEnabled()) {
                logger.debug("Failed to convert bean '" + name + "' to required type '" +
                ClassUtils.getQualifiedName(requiredType) + "'", ex);
            }
            throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
            }
        }
        return (T) bean;
}

看了上方方法我们知道一开始会先判断bean存不存在，如果存在就直接返回了。如果不存在那就要接着往下看`createBean`方法了。

 protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
        if (logger.isDebugEnabled()) {
            logger.debug("Creating instance of bean '" + beanName + "'");
        }
        RootBeanDefinition mbdToUse = mbd;

        // 确保 BeanDefinition 中的 Class 被加载
        Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
        if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
            mbdToUse = new RootBeanDefinition(mbd);
            mbdToUse.setBeanClass(resolvedClass);
        }

        // 准备方法覆写，如果bean中定义了 <lookup-method /> 和 <replaced-method />
        try {
            mbdToUse.prepareMethodOverrides();
        }
        catch (BeanDefinitionValidationException ex) {
            throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
                    beanName, "Validation of method overrides failed", ex);
        }

        try {
            // 如果有代理的话直接返回
            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);
        }
        // 创建 bean 接着往下看
        Object beanInstance = doCreateBean(beanName, mbdToUse, args);
        if (logger.isDebugEnabled()) {
            logger.debug("Finished creating instance of bean '" + beanName + "'");
        }
        return beanInstance;
    }

doCreateBean

 protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) throws BeanCreationException {

        BeanWrapper instanceWrapper = null;
        if (mbd.isSingleton()) {
            //如果是factoryBean则从缓存删除
            instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
        }
        if (instanceWrapper == null) {
            // 实例化 Bean，这个方法里面才是终点，下面说
            instanceWrapper = createBeanInstance(beanName, mbd, args);
        }
        // bean实例
        final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
        // bean类型
        Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
        mbd.resolvedTargetType = beanType;

        synchronized (mbd.postProcessingLock) {
            if (!mbd.postProcessed) {
                try {
                    // 循环调用实现了MergedBeanDefinitionPostProcessor接口的postProcessMergedBeanDefinition方法
                    // Spring对这个接口有几个默认的实现，其中大家最熟悉的一个是操作@Autowired注解的
                    applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
                } catch (Throwable ex) {
                    throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                            "Post-processing of merged bean definition failed", ex);
                }
                mbd.postProcessed = true;
            }
        }
        // 解决循环依赖问题
        boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences && isSingletonCurrentlyInCreation(beanName));
        if (earlySingletonExposure) {
            if (logger.isDebugEnabled()) {
                logger.debug("Eagerly caching bean '" + beanName +
                        "' to allow for resolving potential circular references");
            }
         // 当正在创建A时，A依赖B，此时通过（B将A作为ObjectFactory放入单例工厂中进行early expose，此处B需要引用A，但A正在创建，从单例工厂拿到ObjectFactory，从而允许循环依赖
            addSingletonFactory(beanName, new ObjectFactory<Object>() {
                @Override
                public Object getObject() throws BeansException {
                    return getEarlyBeanReference(beanName, mbd, bean);
                }
            });
        }

        Object exposedObject = bean;
        try {
            // 负责属性装配,很重要，下面说
            populateBean(beanName, mbd, instanceWrapper);
            if (exposedObject != null) {
                // 这里是处理bean初始化完成后的各种回调，例如init-method、InitializingBean 接口、BeanPostProcessor 接口
                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);
            }
        }
        // 同样的，如果存在循环依赖
        if (earlySingletonExposure) {
            Object earlySingletonReference = getSingleton(beanName, false);
            if (earlySingletonReference != null) {
                if (exposedObject == bean) {
                    exposedObject = earlySingletonReference;
                } else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
                    String[] dependentBeans = getDependentBeans(beanName);
                    Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
                    for (String dependentBean : dependentBeans) {
                        if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
                            actualDependentBeans.add(dependentBean);
                        }
                    }
                    if (!actualDependentBeans.isEmpty()) {
                        throw new BeanCurrentlyInCreationException(beanName,
                                "Bean with name '" + beanName + "' has been injected into other beans [" +
                                        StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
                                        "] in its raw version as part of a circular reference, but has eventually been " +
                                        "wrapped. This means that said other beans do not use the final version of the " +
                                        "bean. This is often the result of over-eager type matching - consider using " +
                                        "'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
                    }
                }
            }
        }

        // 把bean注册到相应的Scope中
        try {
            registerDisposableBeanIfNecessary(beanName, bean, mbd);
        } catch (BeanDefinitionValidationException ex) {
            throw new BeanCreationException(
                    mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
        }

        return exposedObject;
    }

到这里第一次初始化的bean也返回了，你以为就这样结束了么。不，还有几个很重要的点 创建bean实例`createBeanInstance ()`

 protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
// 确保已经加载了此 class
        Class<?> beanClass = resolveBeanClass(mbd, beanName);

// 校验类的访问权限
        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());
        }

        if (mbd.getFactoryMethodName() != null) {
// 采用工厂方法实例化
            return instantiateUsingFactoryMethod(beanName, mbd, args);
        }

//是否第一次
        boolean resolved = false;
//是否采用构造函数注入
        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 {
// 无参构造函数
                return instantiateBean(beanName, mbd);
            }
        }

// 判断是否采用有参构造函数
        Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
        if (ctors != null ||
                mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
                mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {
// 构造函数依赖注入
            return autowireConstructor(beanName, mbd, ctors, args);
        }

// 调用无参构造函数
        return instantiateBean(beanName, mbd);
    }

选一个instantiateBean()看一下吧

  protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
        try {
            Object beanInstance;
            final BeanFactory parent = this;
            if (System.getSecurityManager() != null) {
                beanInstance = AccessController.doPrivileged(new PrivilegedAction<Object>() {
                    @Override
                    public Object run() {

                        return getInstantiationStrategy().instantiate(mbd, beanName, parent);
                    }
                }, getAccessControlContext());
            } else {
                // 具体实例化的实现，往下看
                beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
            }
            BeanWrapper bw = new BeanWrapperImpl(beanInstance);
            initBeanWrapper(bw);
            return bw;
        } catch (Throwable ex) {
            throw new BeanCreationException(
                    mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
        }
    }


    public Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner) {

// 如果不存在方法覆写，那就使用 java 反射进行实例化，否则使用 CGLIB,
        if (bd.getMethodOverrides().isEmpty()) {
            Constructor<?> constructorToUse;
            synchronized (bd.constructorArgumentLock) {
                constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;
                if (constructorToUse == null) {
                    final Class<?> clazz = bd.getBeanClass();
                    if (clazz.isInterface()) {
                        throw new BeanInstantiationException(clazz, "Specified class is an interface");
                    }
                    try {
                        if (System.getSecurityManager() != null) {
                            constructorToUse = AccessController.doPrivileged(new PrivilegedExceptionAction<Constructor<?>>() {
                                @Override
                                public Constructor<?> run() throws Exception {
                                    return clazz.getDeclaredConstructor((Class[]) null);
                                }
                            });
                        } else {
                            constructorToUse = clazz.getDeclaredConstructor((Class[]) null);
                        }
                        bd.resolvedConstructorOrFactoryMethod = constructorToUse;
                    } catch (Throwable ex) {
                        throw new BeanInstantiationException(clazz, "No default constructor found", ex);
                    }
                }
            }
// 利用构造方法进行实例化
            return BeanUtils.instantiateClass(constructorToUse);
        } else {
// 存在方法覆写，利用 CGLIB 来完成实例化，需要依赖于 CGLIB 生成子类，这里就不展开了
            return instantiateWithMethodInjection(bd, beanName, owner);
        }
    }

bean属性注入`populateBean ()`

   protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) {
// bean的所有属性
        PropertyValues pvs = mbd.getPropertyValues();

        if (bw == null) {
            if (!pvs.isEmpty()) {
                throw new BeanCreationException(
                        mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
            }
            else {
                return;
            }
        }
        boolean continueWithPropertyPopulation = true;
        if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
            for (BeanPostProcessor bp : getBeanPostProcessors()) {
                if (bp instanceof InstantiationAwareBeanPostProcessor) {
                    InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
// 如果返回 false，代表不需要进行后续的属性设值，也不需要再经过其他的 BeanPostProcessor 的处理
                    if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
                        continueWithPropertyPopulation = false;
                        break;
                    }
                }
            }
        }

        if (!continueWithPropertyPopulation) {
            return;
        }

        if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
                mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
            MutablePropertyValues newPvs = new MutablePropertyValues(pvs);

            // 通过名字找到所有属性值，如果是 bean 依赖，先初始化依赖的 bean。记录依赖关系
            if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
                autowireByName(beanName, mbd, bw, newPvs);
            }

            // 通过类型装配。复杂一些
            if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
                autowireByType(beanName, mbd, bw, newPvs);
            }

            pvs = newPvs;
        }

        boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
        boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);

        if (hasInstAwareBpps || needsDepCheck) {
            PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
            if (hasInstAwareBpps) {
                for (BeanPostProcessor bp : getBeanPostProcessors()) {
                    if (bp instanceof InstantiationAwareBeanPostProcessor) {
                        InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
// 这里就是上方曾经提到过得对@Autowired处理的一个BeanPostProcessor了
// 它会对所有标记@Autowired、@Value 注解的属性进行设值
                        pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
                        if (pvs == null) {
                            return;
                        }
                    }
                }
            }
            if (needsDepCheck) {
                checkDependencies(beanName, mbd, filteredPds, pvs);
            }
        }
// 设置 bean 实例的属性值
        applyPropertyValues(beanName, mbd, bw, pvs);
    }

getBean这一块就搞完了


`finishRefresh()`

protected void finishRefresh() {
//看名字就知道了，清理刚才一系列操作使用到的资源缓存
clearResourceCaches();

      // 初始化LifecycleProcessor
      initLifecycleProcessor();

      // 这个方法的内部实现是启动所有实现了Lifecycle接口的bean
      getLifecycleProcessor().onRefresh();

      //发布ContextRefreshedEvent事件
      publishEvent(new ContextRefreshedEvent(this));

      // 检查spring.liveBeansView.mbeanDomain是否存在，有就会创建一个MBeanServer
      LiveBeansView.registerApplicationContext(this);
}

`resetCommonCaches()`
    最后一步还是清除缓存

`refresh()`总结
上方以及之前的一篇文章，用了这么长的篇幅把整个`refresh()`方法的细节给梳理清楚，这里再把刚开始看的懵懵的`refresh() `方法贴一下

public void refresh() throws BeansException, IllegalStateException {
 
   synchronized (this.startupShutdownMonitor) {

      // 记录容器的启动时间、标记“已启动”状态、检查环境变量
      prepareRefresh();

      // 初始化BeanFactory容器、注册BeanDefinition
      ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

      // 设置 BeanFactory 的类加载器，添加几个 BeanPostProcessor，手动注册几个特殊的 bean
      prepareBeanFactory(beanFactory);

      try {
         // 扩展点
         postProcessBeanFactory(beanFactory);
         // 调用 BeanFactoryPostProcessor 各个实现类的 postProcessBeanFactory(factory) 方法
         invokeBeanFactoryPostProcessors(beanFactory);

         // 注册 BeanPostProcessor 的实现类
         registerBeanPostProcessors(beanFactory);

         // 初始化MessageSource
         initMessageSource();

         // 初始化事件广播器
         initApplicationEventMulticaster();

         // 扩展点
         onRefresh();

         // 注册事件监听器
         registerListeners();


         // 初始化所有的 singleton beans
         finishBeanFactoryInitialization(beanFactory);

         // 广播事件
         finishRefresh();
      }

      catch (BeansException ex) {
         if (logger.isWarnEnabled()) {
            logger.warn("Exception encountered during context initialization - " +
                  "cancelling refresh attempt: " + ex);
         }

         // 销毁已经初始化的的Bean
         destroyBeans();

         // 设置 'active' 状态
         cancelRefresh(ex);

         throw ex;
      }

      finally {
         // 清除缓存
         resetCommonCaches();
      }
   }
}

 

 总结
至此，本文到此结束。鉴于XML方式比较简单、通俗易懂，所以本文基于XML的方式大致介绍了SpringIOC的启动流程、稍微深入的讲解了Bean容器的创建以及Bean的初始化过程。
这也是作者第一次阅读开源框架的源码，如文章有错误之处还请您费心指出。