Spring源码分析3 — spring bean创建和初始化

 2019-11-23 11:03  阅读(1194)
文章分类:Spring Cloud

1 介绍

创建并初始化spring容器中,refresh()方法中解析xml配置文件,注册容器后处理器,bean后处理器,初始化MessageSource,ApplicationEventMulticaster广播器,注册完ApplicationListener监听器后,关键一步就是创建和初始化其他非lazy-init的singleton beans。这样在容器初始化好的时候,这些singleton beans就已经创建和初始化好了,可以大大提高bean的访问效率。这个过程比较复杂,本文将详细分析整个流程。先看涉及到的关键类。

AbstractApplicationContext: 定义了spring容器初始化的大部分流程方法,子类必须遵循这个流程,但可以修改流程中的方法,典型的模板模式。bean创建的入口方法finishBeanFactoryInitialization也在这个方法中。

DefaultListableBeanFactory:一种BeanFactory容器实现,实现了ConfigurableListableBeanFactory接口

BeanDefinition:描述bean结构,对应XML中的或者注解中的@Component

AbstractBeanFactory:继承了BeanFactory容器,主要负责getBean创建Bean实例。

2 流程

2.1 finishBeanFactoryInitialization

初始化spring容器中的refresh()方法中,会调用finishBeanFactoryInitialization()方法,它是创建和初始化其他非lazy-init的singleton的bean的入口。下面从这个方法开始分析。

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
       // 初始化conversionService类型转换bean,它可以服务于其他bean的类型转换
       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));
       }

       // 注册字符串解析器,用来解析注解中的属性
       if (!beanFactory.hasEmbeddedValueResolver()) {
          beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
       }

       // 初始化LoadTimeWeaverAware bean
       String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
       for (String weaverAwareName : weaverAwareNames) {
          getBean(weaverAwareName);
       }

       // 停止使用临时的ClassLoader,
       beanFactory.setTempClassLoader(null);
       beanFactory.freezeConfiguration();

       // 这儿才是最关键的一步,创建和初始化非lazy-init的singleton beans
       beanFactory.preInstantiateSingletons();
    }

finishBeanFactoryInitialization()做了初始化conversionService类型转换器等的工作,这些不是关键点。关键点在preInstantiateSingletons()方法中,它会做创建和初始化singleton bean的工作。下面接着分析

public void preInstantiateSingletons() throws BeansException {
       // 获取XML配置文件解析时,解析到的所有beanname
       List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);

       // 遍历所有没有标注lazy-init的singleton的beanname,创建bean
       for (String beanName : beanNames) {
          // 利用beanname获取BeanDefinition,在XML解析时会生成BeanDefinition对象,将XML中的各属性添加到BeanDefinition的相关标志位中,比如abstractFlag,scope等
          RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
          // 非abstract,非lazy-init的singleton bean才需要在容器初始化阶段创建
          if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
             // 处理FactoryBean
             if (isFactoryBean(beanName)) {
                // 获取FactoryBean实例,FactoryBean前面会加一个&符号
                final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
                boolean isEagerInit;
                if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
                   isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>) () -> ((SmartFactoryBean<?>) factory).isEagerInit(), getAccessControlContext()); } else { isEagerInit = (factory instanceof SmartFactoryBean && ((SmartFactoryBean<?>) factory).isEagerInit()); } if (isEagerInit) { getBean(beanName); } } // 非Factorybean,直接调用getBean方法,关键所在,后续分析 else { getBean(beanName); } } } // bean创建后,对SmartInitializingSingleton回调afterSingletonsInstantiated()方法,这儿不用太care for (String beanName : beanNames) { Object singletonInstance = getSingleton(beanName); if (singletonInstance instanceof SmartInitializingSingleton) { final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance; if (System.getSecurityManager() != null) { AccessController.doPrivileged((PrivilegedAction<Object>) () -> { smartSingleton.afterSingletonsInstantiated(); return null; }, getAccessControlContext()); } else { smartSingleton.afterSingletonsInstantiated(); } } } }

preInstantiateSingletons流程稍微复杂点,主要有

  1. 获取XML解析时的beanNames
  2. 遍历beanNames,获取BeanDefinition。对非abstract,非lazy-init的singleton bean的进行实例化
  3. 如果是FactoryBean,则需要判断isEagerInit,来确定是否调用getBean创建对应的bean。
  4. 如果不是,则直接调用getBean创建对应bean
  5. bean创建后,对SmartInitializingSingleton回调afterSingletonsInstantiated()方法。

2.2 getBean 创建和初始化bean实例

下面我们着重来分析bean的创建,也就是getBean()方法。

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

protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
          @Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {

       // beanname转换,去掉FactoryBean的&前缀,处理alias声明。细节可自行分析
       final String beanName = transformedBeanName(name);
       Object bean;

       Object sharedInstance = getSingleton(beanName);
       if (sharedInstance != null && args == null) {
          // 判断singleton bean是否已经创建好了,创建好了则直接从内存取出。
          bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
       } else {
          // 之前没创建的,则需要创建。
          // 正在创建,则直接异常返回
          if (isPrototypeCurrentlyInCreation(beanName)) {
             throw new BeanCurrentlyInCreationException(beanName);
          }

          // 检查是否有beanname对应的BeanDefinition
          BeanFactory parentBeanFactory = getParentBeanFactory();
          if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
             // 没有找到BeanDefinition,看看parent工厂中有没有,调用parent工厂的getBean
             // 获取原始的name,包含了FactoryBean前缀,&符号
             String nameToLookup = originalBeanName(name);
             if (parentBeanFactory instanceof AbstractBeanFactory) {
                return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
                      nameToLookup, requiredType, args, typeCheckOnly);
             }
             else if (args != null) {
                return (T) parentBeanFactory.getBean(nameToLookup, args);
             }
             else {
                return parentBeanFactory.getBean(nameToLookup, requiredType);
             }
          }

          if (!typeCheckOnly) {
             markBeanAsCreated(beanName);
          }

          try {
             // 找到了beanname对应的BeanDefinition,合并parent的BeanDefinition(XML中的parent属性)
             final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
             checkMergedBeanDefinition(mbd, beanName, args);

             // 处理dependsOn属性
             String[] dependsOn = mbd.getDependsOn();
             if (dependsOn != null) {
                // 遍历所有的dependOn bean,要先注册和创建依赖的bean
                for (String dep : dependsOn) {
                   // check是否两个bean是循环依赖,spring不能出现bean的循环依赖
                   if (isDependent(beanName, dep)) {
                      throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                            "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
                   }
                   // 注册并创建依赖的bean
                   registerDependentBean(dep, beanName);
                   getBean(dep);
                }
             }

             // 处理scope属性
             if (mbd.isSingleton()) {
                // singleton, 必须保证线程安全情况下创建bean,保证单例
                sharedInstance = getSingleton(beanName, () -> {
                   try {
                      // 反射创建bean实例,这个过程很复杂,稍后分析
                      return createBean(beanName, mbd, args);
                   }
                   catch (BeansException ex) {
                      // 异常处理,清除掉bean
                      destroySingleton(beanName);
                      throw ex;
                   }
                });
                // 获取bean实例
                bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
             }
             else if (mbd.isPrototype()) {
                // prototype,创建一个全新的实例
                Object prototypeInstance = null;
                try {
                   // 创建前的回调
                   beforePrototypeCreation(beanName);
                   // 反射创建bean实例,稍后详细分析
                   prototypeInstance = createBean(beanName, mbd, args);
                }
                finally {
                   // 创建后的回调,清除inCreation的标志
                   afterPrototypeCreation(beanName);
                }
                bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
             }

             else {
                // 其他scope值
                String scopeName = mbd.getScope();
                final Scope scope = this.scopes.get(scopeName);
                if (scope == null) {
                   // scope属性不能接收空值
                   throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
                }
                try {
                   Object scopedInstance = scope.get(beanName, () -> {
                      beforePrototypeCreation(beanName);
                      try {
                         return createBean(beanName, mbd, args);
                      }
                      finally {
                         afterPrototypeCreation(beanName);
                      }
                   });
                   bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
                }
                catch (IllegalStateException ex) {
                   throw new BeanCreationException(beanName,
                         "Scope '" + scopeName + "' is not active for the current thread; consider " +
                         "defining a scoped proxy for this bean if you intend to refer to it from a singleton",
                         ex);
                }
             }
          }
          catch (BeansException ex) {
             cleanupAfterBeanCreationFailure(beanName);
             throw ex;
          }
       }
       // check 创建的bean是否是requiredType指明的类型。如果不是,先做转换,转换不成的话只能类型不匹配抛出异常了
       if (requiredType != null && bean != null && !requiredType.isInstance(bean)) {
            try {
                 // 尝试将创建的bean转换为requiredType指明的类型
                return getTypeConverter().convertIfNecessary(bean, requiredType);
            } catch (TypeMismatchException ex) {
                 // 转换不成功,抛出异常
                throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
            }
       } 

       return (T) bean;
    }

doGetBean概括了bean创建和初始化的主要流程,十分复杂,步骤主要为

  1. beanname转换,去掉FactoryBean的&前缀,处理alias声明
  2. 判断singleton bean是否已经创建好了,创建好了则直接从内存取出
  3. 没有创建好,则检查是否有beanname对应的BeanDefinition,没有则到parent工厂中查找,命中则使用parent工厂再次调用getBean以及doGetBean创建
  4. 有BeanDefinition,则合并parent属性指向的中的属性,这主要是处理bean的parent属性。子bean会继承parent bean的属性。
  5. 处理dependsOn属性。必须先创建好所有的依赖的bean
  6. 处理scope属性,如果是singleton的,则必须保证线程安全情况下创建单例。如果是prototype,则必须保证创建一个全新的bean。创建bean通过createBean()反射创建。

2.3 createBean 反射创建bean实例

下面来分析createBean()方法,这个过程也是相当复杂的。

protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
          throws BeanCreationException {
       RootBeanDefinition mbdToUse = mbd;

       // 拷贝一个新的RootBeanDefinition供创建bean使用
       Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
       if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
          mbdToUse = new RootBeanDefinition(mbd);
          mbdToUse.setBeanClass(resolvedClass);
       }

       // 处理bean中定义的覆盖方法,主要是xml:lookup-method或replace-method。标记override的方法为已经加载过的,避免不必要的参数检查开销。这儿不详细展开了。
       try {
          mbdToUse.prepareMethodOverrides();
       }
       catch (BeanDefinitionValidationException ex) {
          throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
                beanName, "Validation of method overrides failed", ex);
       }

       // 调用BeanPostProcessors bean后处理器,使得bean后处理器可以返回一个proxy bean,从而代替我们要创建的bean。回调后处理器的postProcessBeforeInstantiation()方法,如果这个方法中返回了一个bean,也就是使用了proxy,则再回调postProcessAfterInitialization()方法。之后返回这个Proxy bean即可。
       try {
          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);
       }

       // doCreateBean创建bean实例,后面详细分析
       try {
          Object beanInstance = doCreateBean(beanName, mbdToUse, args);
          return beanInstance;
       }
       // 各种异常,省略
       ... 
    }

createBean()方法大概步骤如下

  1. 拷贝一个新的RootBeanDefinition供创建bean使用
  2. 处理lookup-method或replace-method
  3. 调用BeanPostProcessors后处理器
  4. doCreateBean创建bean实例

下面我们重点分析doCreateBean方法

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

       // 创建bean实例,如果是singleton,先尝试从缓存中取,取不到则创建
       BeanWrapper instanceWrapper = null;
       if (mbd.isSingleton()) {
          instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
       }
       if (instanceWrapper == null) {
          // 反射创建bean实例,后面详细说
          instanceWrapper = createBeanInstance(beanName, mbd, args);
       }
       final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
       Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
       mbd.resolvedTargetType = beanType;

       // 回调MergedBeanDefinitionPostProcessor.postProcessMergedBeanDefinition,它可以修改bean属性
       if (beanType != null) {
          synchronized (mbd.postProcessingLock) {
             if (!mbd.postProcessed) {
                try {
                   applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
                }
                catch (Throwable ex) {
                   throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                         "Post-processing of merged bean definition failed", ex);
                }
                mbd.postProcessed = true;
             }
          }
       }

       // 曝光单例对象的引用,主要是为了解决单例间的循环依赖问题,以及依赖的bean比较复杂时的初始化性能问题
       boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
             isSingletonCurrentlyInCreation(beanName));
       if (earlySingletonExposure) {
          addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean)); } // 初始化bean,后面详细介绍 Object exposedObject = bean; try { populateBean(beanName, mbd, instanceWrapper); if (exposedObject != null) { exposedObject = initializeBean(beanName, exposedObject, mbd); } } // 省略异常处理 // 单例曝光对象的处理,不用太在意 if (earlySingletonExposure) { Object earlySingletonReference = getSingleton(beanName, false); if (earlySingletonReference != null) { if (exposedObject == bean) { exposedObject = earlySingletonReference; } else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) { String[] dependentBeans = getDependentBeans(beanName); Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length); for (String dependentBean : dependentBeans) { if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) { actualDependentBeans.add(dependentBean); } } if (!actualDependentBeans.isEmpty()) { // 抛出异常,省略代码 } } } } // 注册bean为可销毁的bean,bean销毁时,会回调destroy-method if (bean != null) { try { registerDisposableBeanIfNecessary(beanName, bean, mbd); } catch (BeanDefinitionValidationException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex); } } return exposedObject; }

doCreateBean方法主要流程为

  1. createBeanInstance() 创建bean实例
  2. 回调postProcessMergedBeanDefinition(), 可以修改bean属性
  3. initializeBean() 初始化bean实例,包括后处理器的调用,init-method的调用等
  4. 注册bean为可销毁的,这样在bean销毁时,就可以回调到destroy-method.

2.3.1 createBeanInstance 反射创建bean实例

我们先分析如何创建bean实例的。

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
       // 先创建class对象,反射的套路。利用bean的class属性进行反射,所以class属性一定要是bean的实现类
       Class<?> beanClass = resolveBeanClass(mbd, beanName);

       // class如果不是public的,则抛出异常。因为没法进行实例化
       if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
          throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                "Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
       }

       // 
       Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
       if (instanceSupplier != null) {
          return obtainFromSupplier(instanceSupplier, beanName);
       }

       // 使用FactoryBean的factory-method来创建,支持静态工厂和实例工厂
       if (mbd.getFactoryMethodName() != null)  {
          return instantiateUsingFactoryMethod(beanName, mbd, args);
       }

       // 无参数情况时,创建bean。调用无参构造方法
       boolean resolved = false;
       boolean autowireNecessary = false;
       if (args == null) {
          synchronized (mbd.constructorArgumentLock) {
             if (mbd.resolvedConstructorOrFactoryMethod != null) {
                resolved = true;
                autowireNecessary = mbd.constructorArgumentsResolved;
             }
          }
       }
       if (resolved) {
          if (autowireNecessary) {
             // autoWire创建 自动装配
             return autowireConstructor(beanName, mbd, null, null);
          }
          else {
             // 普通创建
             return instantiateBean(beanName, mbd);
          }
       }

       // 有参数情况时,创建bean。先利用参数个数,类型等,确定最精确匹配的构造方法。
       Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
       if (ctors != null ||
             mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
             mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args))  {
          return autowireConstructor(beanName, mbd, ctors, args);
       }

       // 有参数时,又没获取到构造方法,则只能调用无参构造方法来创建实例了(兜底方法)
       return instantiateBean(beanName, mbd);
    }

instantiateBean,使用无参构造方法,反射创建bean实例代码如下

protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
       try {
          Object beanInstance;
          final BeanFactory parent = this;
          if (System.getSecurityManager() != null) {
             beanInstance = AccessController.doPrivileged((PrivilegedAction<Object>) () -> getInstantiationStrategy().instantiate(mbd, beanName, parent), getAccessControlContext()); } else { // 创建实例,关键点,其他都不用care 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); } }

这个方法没什么要注意的,关键点在instantiate方法

public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
       // Don't override the class with CGLIB if no overrides.
       if (bd.getMethodOverrides().isEmpty()) {
          Constructor<?> constructorToUse;
          // 保证线程安全情况下,获取Constructor
          synchronized (bd.constructorArgumentLock) {
             // 获取构造方法或factory-method
             constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;
             if (constructorToUse == null) {
                // BeanDefinition中如果没有Constructor或者factory-method,则直接使用默认无参构造方法。
                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(
                            (PrivilegedExceptionAction<Constructor<?>>) () ->
                                  clazz.getDeclaredConstructor());
                   }
                   else {
                      // 获取默认无参构造方法
                      constructorToUse = clazz.getDeclaredConstructor();
                   }
                   bd.resolvedConstructorOrFactoryMethod = constructorToUse;
                }
                catch (Throwable ex) {
                   throw new BeanInstantiationException(clazz, "No default constructor found", ex);
                }
             }
          }
          // 使用上一步得到的Constructor,反射获取bean实例
          return BeanUtils.instantiateClass(constructorToUse);
       }
       else {
          // Must generate CGLIB subclass.
          return instantiateWithMethodInjection(bd, beanName, owner);
       }
    }

instantiate方法主要做两件事

  1. 确定Constructor或者factory-method
  2. 利用Constructor,反射创建bean实例。

分析到这儿Bean的创建就结束了,这个过程实在是太复杂了!

2.3.2 initializeBean 初始化bean实例

bean创建完后,容器会对它进行初始化,包括后处理的调用,init-method的调用等。请看下面详解。

protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
       // 回调各种aware method,如BeanNameAware, BeanFactoryAware等
       if (System.getSecurityManager() != null) {
          AccessController.doPrivileged((PrivilegedAction<Object>) () -> { invokeAwareMethods(beanName, bean); return null; }, getAccessControlContext()); } else { invokeAwareMethods(beanName, bean); } // 回调beanPostProcessor的postProcessBeforeInitialization()方法 Object wrappedBean = bean; if (mbd == null || !mbd.isSynthetic()) { wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName); } // init-method 和 postProcessAfterInitialization if (wrappedBean != null) { try { // 回调init-method invokeInitMethods(beanName, wrappedBean, mbd); } catch (Throwable ex) { throw new BeanCreationException( (mbd != null ? mbd.getResourceDescription() : null), beanName, "Invocation of init method failed", ex); } // 回调beanPostProcessor的postProcessAfterInitialization()方法 if (mbd == null || !mbd.isSynthetic()) { wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName); } } return wrappedBean; }

由此可见,initializeBean(),也就是bean的初始化流程为

  1. 回调各种aware method,如BeanNameAware,将容器中相关引用注入到bean中,供bean使用
  2. 回调beanPostProcessor的postProcessBeforeInitialization(), 后处理器的初始化前置调用
  3. 回调init-method, 注解和XML中都可以声明
  4. 回调beanPostProcessor的postProcessAfterInitialization()方法,后处理器的初始化后置调用。

从这个流程,我们也能清晰的分析出容器后处理器两个方法的调用时机。分析源码可以大大加深我们对spring API的理解。

3 总结

Bean实例的创建和初始化流程还是十分复杂的。从源码中可以清晰的分析出spring bean的各种特性。如factory-method, BeanPostProcessor等。有助于我们spring bean行为的理解。所以分析源码还是十分值得的。

转载至:http://blog.csdn.net/u013510838/article/details/75126299


来源:http://ddrv.cn/a/88268

点赞(0)
版权归原创作者所有,任何形式转载请联系作者; Java 技术驿站 >> Spring源码分析3 — spring bean创建和初始化

相关推荐