原文链接：https://my.oschina.net/u/3995125/blog/3080324

SpringBean的生命周期

一：单例与多例对象是如何初始化

单例默认情况下是在容器被加载的时候就会初始化

多例是在每次获取Bean对象的时候初始化

代码验证：

@Component
public class UserEntity {
public UserEntity() {
System.out.println(">>>>UserEntity无参数构造函数执行...");
}

@Configuration
@ComponentScan("com.mayikt.entity")
public class MyConfig {
}

>>>>UserEntity无参数构造函数执行...

当加上@Scope("prototype")，没有输出结果

@Component
@Scope("prototype")
public class UserEntity {
public UserEntity() {
System.out.println(">>>>UserEntity无参数构造函数执行...");
}

说明单例默认是在容器被加载的时候初始化，多例是在每次获取Bean对象的时候初始化。

二：Bean对象的初始化与销毁过程01

Bean初始化：指的就是对象已经创建，里面的所有set方法都已经执行完毕了。

举个例子：

@Configuration
@ComponentScan("com.mayikt.entity")
public class MyConfig {

/**
* initMethod：指定初始化方法执行
* destroyMethod：指定销毁方法
* @return
*/
@Bean(initMethod = "initMethod",destroyMethod = "destroyMethod")
public UserEntity userEntity(){
return new UserEntity();
}
}

@Component
public class UserEntity {
public UserEntity() {
System.out.println(">>>>UserEntity无参数构造函数执行...");
}
/**
* 思考：initMethod是在无参构造函数之前执行还是后执行..
*/
private void initMethod() {
System.out.println(">>>>UserEntity initMethod 执行...");
}
private void destroyMethod() {
System.out.println(">>>>UserEntity destroyMethod 执行...");
}
}

public static void main(String[] args) {
/**
* IOC容器初始化单例对象都是循环遍历调用getBean方法
*/
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MyConfig.class);
applicationContext.close();

返回结果

>>>>UserEntity无参数构造函数执行...
>>>>UserEntity initMethod 执行...
>>>>UserEntity destroyMethod 执行...

构造函数：Bean的创建，Map集合存储对象

initMethod：表示对象已经创建成功之后执行

destroyMethod：表示对象被销毁之后执行，clean

destroyMethod方法执行时，相当于调用了close方法去销毁Bean

applicationContext.close();

public void close() {
synchronized (this.startupShutdownMonitor) {
doClose();
// If we registered a JVM shutdown hook, we don't need it anymore now:
// We've already explicitly closed the context.
if (this.shutdownHook != null) {
try {
Runtime.getRuntime().removeShutdownHook(this.shutdownHook);
}
catch (IllegalStateException ex) {
// ignore - VM is already shutting down
}
}
}
}

protected void doClose() {
if (this.active.get() && this.closed.compareAndSet(false, true)) {
....
// Destroy all cached singletons in the context's BeanFactory.
destroyBeans();

// Close the state of this context itself.
closeBeanFactory();

// Let subclasses do some final clean-up if they wish...
onClose();

this.active.set(false);
}
}

protected void destroyBeans() {
getBeanFactory().destroySingletons();
}

public void destroySingletons() {
super.destroySingletons();
this.manualSingletonNames.clear();
this.clearByTypeCache();
}

private void clearByTypeCache() {
this.allBeanNamesByType.clear();
this.singletonBeanNamesByType.clear();
}

上面执行了clear操作，再回到前面

这里给用户自定义关闭操作：模板方法设计模式

protected void onClose() {
// For subclasses: do nothing by default.
}

再把活跃状态设置为false。

三：Bean对象的初始化与销毁过程02

1.实现InitializingBean,DisposableBean两个接口

@Component
public class MemberEntity implements InitializingBean,DisposableBean{
//     implements InitializingBean, DisposableBean
public MemberEntity() {
System.out.println("无参构造函数执行..");
}
// afterPropertiesSet initMet hod
// 1.对象创建 对象属性赋值 set方法全部走完
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("MemberEntity >>>afterPropertiesSet");
}
@Override
public void destroy() throws Exception {
System.out.println("MemberEntity >>> destroy");
}
}

输出结果：

无参构造函数执行..
MemberEntity >>>afterPropertiesSet
MemberEntity >>> destroy

2.使用Java封装的注解方式@PostConstruct， @PreDestroy

@Component
public class MemberEntity{
//     implements InitializingBean, DisposableBean
public MemberEntity() {
System.out.println("无参构造函数执行..");
}
// afterPropertiesSet initMet hod
// 1.对象创建 对象属性赋值 set方法全部走完
  @PostConstruct
public void afterPropertiesSet() throws Exception {
System.out.println("MemberEntity >>>afterPropertiesSet");
}
 @PreDestroy
public void destroy() throws Exception {
System.out.println("MemberEntity >>> destroy");
}
}

输出结果

无参构造函数执行..
MemberEntity >>>afterPropertiesSet
MemberEntity >>> destroy

四：现在我们开始分析SpringBean的生命周期

SpringBean生命周期有个很好的理念就是后置处理器BeanPostProcessor

后置处理器：BeanPostProcessor

BeanPostProcessor引入：

@Component
public class MyApplicationContext implements ApplicationContextAware {
private ApplicationContext applicationContext;
/**
* spring底层中为什么能够实现ApplicationContextAware接口 就能够拿到ApplicationContext
* @param applicationContext
* @throws BeansException
*/
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
MemberEntity memberEntity = applicationContext.getBean("memberEntity", MemberEntity.class);
System.out.println("memberEntity：" + memberEntity);
}
}

@Configuration
@ComponentScan("com.mayikt.entity")
@Import(MyApplicationContext.class)//这里注入到spring容器中
public class MyConfig {}

输出结果：对象初始化，赋值完毕，就可以通过setApplicationContext拿到bean对象

memberEntity：com.mayikt.entity.MemberEntity@11e21d0e

思考问题：spring底层中为什么能够实现ApplicationContextAware接口 就能够拿到ApplicationContext

关键就是在于：BeanPostProcessor

下面我们开始分析：BeanPostProcessor后置处理器（非常重要！！！）

AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MyConfig.class);

public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
this();
register(annotatedClasses);
refresh();
}

public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
....
try {
....
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
}
....
}

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
....
// Instantiate all remaining (non-lazy-init) singletons.
beanFactory.preInstantiateSingletons();
}

@Override
public void preInstantiateSingletons() throws BeansException {
    ....
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);

for (String beanName : beanNames) {
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
if (isFactoryBean(beanName)) {
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);
}
}
else {
getBean(beanName);
}
}
}
....
}

@Override
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 {
....
Object sharedInstance = getSingleton(beanName);//检测缓存中或者实例工厂中是否有对应的实例
if (sharedInstance != null && args == null) {
if (logger.isDebugEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);//返回对应的实例，有时候存在诸如BeanFactory的情况并不是直接返回实例本身而是返回指定方法返回的实例
}

else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {//只有在单例情况下才会去尝试解决循环依赖
throw new BeanCurrentlyInCreationException(beanName);
}

// Check if bean definition exists in this factory.
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {//如果beaanDefinitionMap中也就是在所有已经加载的类中不包括beanName则尝试从parentBeanFactory中检测
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (parentBeanFactory instanceof AbstractBeanFactory) {
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {//递归到BeanFactory中寻找
// Delegation to parent with explicit args.
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else {
// No args -> delegate to standard getBean method.
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
}

if (!typeCheckOnly) {//如果不是仅仅做类型检查，则是创建Bean，这里进行记录
markBeanAsCreated(beanName);
}

try {
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);//转换为RootBeanDefinition
checkMergedBeanDefinition(mbd, beanName, args);

// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {//若存在依赖则需要递归实例化依赖的Bean
for (String dep : dependsOn) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);//缓存依赖调用
getBean(dep);
}
}

// Create bean instance.
if (mbd.isSingleton()) {//实例化依赖的bean后，便可实例化mbd本身了，单例模式的创建
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}

else if (mbd.isPrototype()) {//prototype模式的创建
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}

else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, () -> {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
});
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 if required type matches the type of the actual bean instance.
if (requiredType != null && !requiredType.isInstance(bean)) {//检测需要的类型是否符合实际bean的类型
try {
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
if (convertedBean == null) {
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
return convertedBean;
}
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;
}

步骤大致如下：

1.转换BeanName

2.尝试从缓存中加载单例bean

3.Bean的实例化

4.原型模式的依赖检查

5.检查parentBeanFactory

6.将存储XML配置文件的GernericBeanDefinition转换为RootBeanDefinition

7.寻找依赖

8.针对不同的scope进行bean的创建

9.类型转换

判断是单例：

if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}

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

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

final Object bean = instanceWrapper.getWrappedInstance();
....
Object exposedObject = bean;
try {
populateBean(beanName, mbd, instanceWrapper);//循环给属性赋值
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
....
}

protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {
AccessController.doPrivileged(() -> {
this.invokeAwareMethods(beanName, bean);
return null;
}, this.getAccessControlContext());
} else {
this.invokeAwareMethods(beanName, bean);
}

Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = this.applyBeanPostProcessorsBeforeInitialization(bean, beanName);
}

try {
this.invokeInitMethods(beanName, wrappedBean, mbd);//执行自定义的init方法
} catch (Throwable var6) {
throw new BeanCreationException(mbd != null ? mbd.getResourceDescription() : null, beanName, "Invocation of init method failed", var6);
}

if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = this.applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}

return wrappedBean;
}

private void invokeAwareMethods(String beanName, Object bean) {
if (bean instanceof Aware) {
if (bean instanceof BeanNameAware) {    //判断类型并设置beanName
((BeanNameAware)bean).setBeanName(beanName);
}

if (bean instanceof BeanClassLoaderAware) {
ClassLoader bcl = this.getBeanClassLoader();
if (bcl != null) {
((BeanClassLoaderAware)bean).setBeanClassLoader(bcl);
}
}
if (bean instanceof BeanFactoryAware) {
((BeanFactoryAware)bean).setBeanFactory(this);
}
}
}

我们就明白了：IOC容器初始化单例对象都是循环遍历调用getBean方法。

下面我们手写看下springBean的生命周期

@Component
public class PayEntity implements BeanNameAware, BeanFactoryAware, InitializingBean, ApplicationContextAware {
public PayEntity() {
System.out.println("1.对象的实例化完成..");
}

@Override
public void setBeanName(String name) {
System.out.println("2.对象beanName:" + name);
}
@Override
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
System.out.println("3.beanFactory:" + beanFactory);
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
System.out.println("4.获取到applicationContext对象");
}
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("5.bean init方法执行..");
}

输出结果

1.对象的实例化完成..
2.对象beanName:payEntity
3.beanFactory:org.springframework.beans.factory.support.DefaultListableBeanFactory@55f3ddb1: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.event.internalEventListenerProcessor,org.springframework.context.event.internalEventListenerFactory,myConfig,payEntity]; root of factory hierarchy
4.获取到applicationContext对象
5.bean init方法执行..

BeanPostProcessor的作用

protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
....
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);//init之前处理操作
}
....
try {
invokeInitMethods(beanName, wrappedBean, mbd);//init执行逻辑
}
....
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);//init之后处理操作
}

return wrappedBean;
}

BeanPostProcessor后置处理器的前置处理逻辑和后置处理逻辑:

public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
throws BeansException {
for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
Object current = beanProcessor.postProcessBeforeInitialization(result, beanName);
   ...
}

public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
throws BeansException {
for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
Object current = beanProcessor.postProcessAfterInitialization(result, beanName);
...
}

我们自定义类实现BeanPostProcessor

@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
//BeanPostProcessor 后置处理器 对我们bean的对象实现增强
@Override
// 执行自定义init方法之前处理
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
System.out.println("执行init方法之前处理 : " + beanName);
return bean;
}

@Override
// 执行自定义init方法之后处理
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
System.out.println("执行init方法之后处理 :" + beanName);
return bean;
}
//BeanPostProcessor  后置处理
// Aware    实现
}

输出结果：

执行init方法之前处理 : org.springframework.context.event.internalEventListenerProcessor
执行init方法之后处理 :org.springframework.context.event.internalEventListenerProcessor
执行init方法之前处理 : org.springframework.context.event.internalEventListenerFactory
执行init方法之后处理 :org.springframework.context.event.internalEventListenerFactory
执行init方法之前处理 : myConfig
执行init方法之后处理 :myConfig
1.对象的实例化完成..
2.对象beanName:payEntity
3.beanFactory:org.springframework.beans.factory.support.DefaultListableBeanFactory@55f3ddb1: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.event.internalEventListenerProcessor,org.springframework.context.event.internalEventListenerFactory,myConfig,payEntity,com.mayikt.processor.MyBeanPostProcessor]; root of factory hierarchy
4.获取到applicationContext对象
执行init方法之前处理 : payEntity
5.bean init方法执行..
执行init方法之后处理 :payEntity

ApplicationAware接口原理

实现ApplicationAware接口怎么就可以setApplicationContext呢？

@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
System.out.println("4.获取到applicationContext对象");
}

public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
throws BeansException {

Object result = existingBean;
for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
Object current = beanProcessor.postProcessAfterInitialization(result, beanName);
if (current == null) {
return result;
}
result = current;
}
return result;
}

@Override
public Object postProcessAfterInitialization(Object bean, String beanName) {
return bean;
}

发现BeanPostProcessor后置处理器的postProcessAfterInitialization后置处理什么也没做:

再去前置找：

public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
throws BeansException {

Object result = existingBean;
for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
Object current = beanProcessor.postProcessBeforeInitialization(result, beanName);
if (current == null) {
return result;
}
result = current;
}
return result;
}

public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {
AccessControlContext acc = null;

if (System.getSecurityManager() != null &&
(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) {
acc = this.applicationContext.getBeanFactory().getAccessControlContext();
}

if (acc != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareInterfaces(bean);
return null;
}, acc);
}
else {
invokeAwareInterfaces(bean);
}

return bean;
}

private void invokeAwareInterfaces(Object bean) {
if (bean instanceof Aware) {
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);
}
if (bean instanceof ApplicationContextAware) {//判断ApplicationContextAware类型，赋值
((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
}
}
}

看到没有，最后判断：bean instanceof ApplicationContextAware类型，再赋值

我们就可以知道上面提出的这个问题：实现ApplicationAware接口怎么就可以setApplicationContext？

所以我们知道ApplicationContextAware是通过BeanPostProcessor后置处理器的postProcessBeforeInitialization前置处理实现的。

SpringBean的生命周期总结

源码分析流程：

1.进入到刷新refresh（）方法

2.finishBeanFactoryInitialization（）初始化所有单例对象

3.preInstantiateSingletons（）初始化所有的单例对象：注意是非懒加载

4.getBean（）-》doGetBean（）先查询该对象是否有初始化过，没有的化就创建注册到IOC容器中

5.createBean（）判断对象如果是单例的情况下，就调用该方法去创建对象

6.doCreateBean（）创建IOC对象

7.createBeanInstance（）使用Java的反射机制实例化我们的对象

8.populateBean（）给对象的set属性赋值

9.initializeBean（）执行初始化方法（也可以自己定义初始化的方法）

10.invokeAwareMethods（）判断bean的类型是否是Aware相关依赖，如果存在的情况回调方法

11.applyBeanPostProcessorsBeforeInitialization（）在初始化方法之前执行处理（增强）

12.invokeInitMethods（）调用自定义的init方法，Java反射技术

13.applyBeanPostProcessorsAfterInitialization（）在初始化方法之后执行处理（增强）

14.正常是用我们初始化好的这个Bean对象

15.销毁bean

本文参考

参考书籍：Spring源码深度解析

蚂蚁课堂：http://www.mayikt.com/

 

转载于:https://my.oschina.net/u/3995125/blog/3080324