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Spring refresh()源码解析

时间：2023-03-15来源：系统城装机大师作者：佚名

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40 public void refresh() throws BeansException, IllegalStateException {
synchronized(this.startupShutdownMonitor) {
// 1. 初始化前的预处理
this.prepareRefresh();
// 2. 刷新Bean工厂
ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
// 3. BeanFactory的预处理配置
this.prepareBeanFactory(beanFactory);
try {
// 4. BeanFactory的后置处理
this.postProcessBeanFactory(beanFactory);
// 5. 执行BeanFactory后置处理器
this.invokeBeanFactoryPostProcessors(beanFactory);
// 6. 注册Bean的后置处理器
this.registerBeanPostProcessors(beanFactory);
// 7. 初始化MessageSource
this.initMessageSource();
// 8. 初始化事件派发器
this.initApplicationEventMulticaster();
// 9. 子类的多态onRefresh
this.onRefresh();
// 10. 注册监听器
this.registerListeners();
// 11. 初始化所有剩下的单例Bean
this.finishBeanFactoryInitialization(beanFactory);
// 12. 完成容器的创建工作
this.finishRefresh();
} catch (BeansException var9) {
if (this.logger.isWarnEnabled()) {
this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt: " + var9);
}
this.destroyBeans();
this.cancelRefresh(var9);
throw var9;
} finally {
// 13. 清除缓存
this.resetCommonCaches();
}
}
}

一、prepareRefresh：初始化前的预处理

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20 protected void prepareRefresh() {
//设置容器启动时间
this.startupDate = System.currentTimeMillis();
//设置容器关闭状态为false
this.closed.set(false);
//设置容器激活状态为true
this.active.set(true);
if (this.logger.isDebugEnabled()) {
if (this.logger.isTraceEnabled()) {
this.logger.trace("Refreshing " + this);
} else {
this.logger.debug("Refreshing " + this.getDisplayName());
}
}
//1.1初始化属性资源
this.initPropertySources();
//1.2校验
this.getEnvironment().validateRequiredProperties();
this.earlyApplicationEvents = new LinkedHashSet();
}

1.1初始化属性值

初始化方法是个模压方法，由子类重写

1 2	`protected` `void` `initPropertySources() {` `}`

Web容器GenericWebApplicationContext重写了此方法

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8 protected void initPropertySources() {
//获取环境信息
ConfigurableEnvironment env = getEnvironment();
//判断是否是web配置环境
if (env instanceof ConfigurableWebEnvironment) {
((ConfigurableWebEnvironment) env).initPropertySources(this.servletContext, null);
}
}

最终由StandardServletEnvironment进行初始化

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4 public void initPropertySources(@Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {
//使用web容器工具初始化
WebApplicationContextUtils.initServletPropertySources(getPropertySources(), servletContext, servletConfig);
}

把 Servlet 的一些初始化参数放入IOC容器中

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11 public static void initServletPropertySources(MutablePropertySources sources, @Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {
Assert.notNull(sources, "'propertySources' must not be null");
String name = "servletContextInitParams";
if (servletContext != null && sources.contains(name) && sources.get(name) instanceof StubPropertySource) {
sources.replace(name, new ServletContextPropertySource(name, servletContext));
}
name = "servletConfigInitParams";
if (servletConfig != null && sources.contains(name) && sources.get(name) instanceof StubPropertySource) {
sources.replace(name, new ServletConfigPropertySource(name, servletConfig));
}
}

1.2属性校验

通过占位符解析器校验资源集合

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3 public void validateRequiredProperties() throws MissingRequiredPropertiesException {
this.propertyResolver.validateRequiredProperties();
}

这里的解析器作为常量在环境被实例化时就被创建出来的，PropertySourcesPropertyResolver是占位符解析器，将数据源中占位符替换成目标值

校验是否有需要被占位符修饰的属性，如果有但是资源中找不到对应属性的key就会抛出异常

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11 public void validateRequiredProperties() {
MissingRequiredPropertiesException ex = new MissingRequiredPropertiesException();
for (String key : this.requiredProperties) {
if (this.getProperty(key) == null) {
ex.addMissingRequiredProperty(key);
}
}
if (!ex.getMissingRequiredProperties().isEmpty()) {
throw ex;
}
}

案例： 资源文件

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4 name=zhansan
age=${name},10
encoding=utf-8
name2=${name}

测试代码

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8 @Test
public void test1() throws Exception {
//省略propertySources
PropertyResolver propertyResolver = new PropertySourcesPropertyResolver(getPropertySources());
System.out.println(propertyResolver.getProperty("age"));
System.out.println(propertyResolver.getProperty("encoding"));
System.out.println(propertyResolver.resolvePlaceholders("must be encoding ${encoding}")); //输出must be encoding gbk
}

输出结果

10,zhansan
utf-8
must be encoding utf-8

二、obtainFreshBeanFactory：刷新Bean工厂

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5 protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
//2.1刷新Bean工厂
refreshBeanFactory();
return getBeanFactory();
}

将容器刷新标识改为true，并且设置了工厂序列化id

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7 protected final void refreshBeanFactory() throws IllegalStateException {
if (!this.refreshed.compareAndSet(false, true)) {
throw new IllegalStateException(
"GenericApplicationContext does not support multiple refresh attempts: just call 'refresh' once");
}
this.beanFactory.setSerializationId(getId());
}

三、prepareBeanFactory：Bean工厂预处理

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37 protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// 设置BeanFactory的类加载器、表达式解析器等
beanFactory.setBeanClassLoader(getClassLoader());
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// 3.1 添加Aware执行器
beanFactory.addBeanPostProcessor(new ApplicationContextDProcessor(this));
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
// 3.2 自动注入的支持
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// 3.3 添加监听器执行器
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// Detect a LoadTimeWeaver and prepare for weaving, if found.
if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
// Set a temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
// Register default environment beans.
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}

3.1 ApplicationContextDProcessor：Aware执行器

ApplicationContextDProcessor实现了BeanPostProcessor的postProcessBeforeInitialization接口，在所有Bean初始化前会执行当前方法

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23 public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
//判断Bean是Aware的子类
if (!(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)){
return bean;
}
AccessControlContext acc = null;
if (System.getSecurityManager() != null) {
acc = this.applicationContext.getBeanFactory().getAccessControlContext();
}
if (acc != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareInterfaces(bean);
return null;
}, acc);
}
else {
//回调执行Aware接口
invokeAwareInterfaces(bean);
}
return bean;
}

如果当前Bean是Aware的子类，那么将Bean强转成Aware类型，通过回调将信息设置到Bean中

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20 private void invokeAwareInterfaces(Object bean) {
if (bean instanceof EnvironmentAware) {
((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
}
if (bean instanceof EmbeddedValueResolverAware) {
((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
}
if (bean instanceof ResourceLoaderAware) {
((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
}
if (bean instanceof ApplicationEventPublisherAware) {
((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
}
if (bean instanceof MessageSourceAware) {
((MessageSourceAware) bean).setMessageSource(this.applicationContext);
}
if (bean instanceof ApplicationContextAware) {
((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
}
}

3.2 registerResolvableDependency：自动注入的支持

如果过容器中有多个相同接口的实现类，那么在自动注入的时候会注入注册的实现类

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4 beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);

3.3 添加监听器执行器

ApplicationListenerDetector主要作用是添加和销毁监听器,实现了BeanPostProcessor的postProcessAfterInitialization（Bean实例化之后）方法和DestructionAwareBeanPostProcessor的postProcessBeforeDestruction（Bean销毁之前）方法

详情：https://www.jb51.net/article/277948.htm

四、BeanFactory的后置处理

这是个模压方法,由子类AnnotationConfigServletWebServerApplicationContext实现

1 2	`protected` `void` `postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {` `}`

AnnotationConfigServletWebServerApplicationContext首先调了父类 ServletWebServerApplicationContext 的 postProcessBeanFactory 方法

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11 protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
//4.1后置处理Bean工厂
super.postProcessBeanFactory(beanFactory);
if (this.basePackages != null && this.basePackages.length > 0) {
//basePackages为空不会执行
this.scanner.scan(this.basePackages);
}
if (!this.annotatedClasses.isEmpty()) {
this.reader.register(ClassUtils.toClassArray(this.annotatedClasses));
}
}

4.1 后置处理bean工厂

父类ServletWebServerApplicationContext首先向Bean工厂中注入了一个执行器

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7 protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
//4.1.1注入执行器
beanFactory.addBeanPostProcessor(new WebApplicationContextServletContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(ServletContextAware.class);
//4.1.2注册作用域
registerWebApplicationScopes();
}

4.1.1 WebApplicationContextServletContextAwareProcessor

WebApplicationContextServletContextAwareProcessor继承了ServletContextAwareProcessor

ServletContextAwareProcessor继承了BeanPostProcessor实现了postProcessBeforeInitialization（Bean初始化前执行）

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11 public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
//注入ServletContext
if (getServletContext() != null && bean instanceof ServletContextAware) {
((ServletContextAware) bean).setServletContext(getServletContext());
}
//注入ServletConfig
if (getServletConfig() != null && bean instanceof ServletConfigAware) {
((ServletConfigAware) bean).setServletConfig(getServletConfig());
}
return bean;
}

4.1.2 registerWebApplicationScopes 注册web的应用域

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6 // 所在类及方法：ServletWebServerApplicationContext#registerWebApplicationScopes
private void registerWebApplicationScopes() {
ExistingWebApplicationScopes existingScopes = new ExistingWebApplicationScopes(getBeanFactory());
WebApplicationContextUtils.registerWebApplicationScopes(getBeanFactory());
existingScopes.restore();
}

ExistingWebApplicationScopes是ServletWebServerApplicationContext类中的一个静态类

源码如下：

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29 public static class ExistingWebApplicationScopes {
static {
Set<String> scopes = new LinkedHashSet<>();
scopes.add(WebApplicationContext.SCOPE_REQUEST);
scopes.add(WebApplicationContext.SCOPE_SESSION);
SCOPES = Collections.unmodifiableSet(scopes);
}
// 这是构造方法，大概就是根据SCOPES获取beanFactory中已经注册的scope，然后放入scopes
// 需要注意的是，在上面的方法中，第二行才在向beanFactory中注册，也就是这时的beanFactory里面没有request和session这两个scop
// 所以这里就完成了beanFactory的赋值。建议打断点进去看看
public ExistingWebApplicationScopes(ConfigurableListableBeanFactory beanFactory) {
this.beanFactory = beanFactory;
for (String scopeName : SCOPES) {
Scope scope = beanFactory.getRegisteredScope(scopeName);
if (scope != null) {
this.scopes.put(scopeName, scope);
}
}
}
// 由于上面的方法并没有值存入scopes，所以这里也就没执行里面的内容
public void restore() {
this.scopes.forEach((key, value) -> {
if (logger.isInfoEnabled()) {
logger.info("Restoring user defined scope " + key);
}
this.beanFactory.registerScope(key, value);
});
}
}

WebApplicationContextUtils.registerWebApplicationScopes()，这个方法就是向beanFactory注册web的scope了，源码如下

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23 public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory) {
registerWebApplicationScopes(beanFactory, null);
}
public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory,
@Nullable ServletContext sc) {
// 注册作用域
beanFactory.registerScope(WebApplicationContext.SCOPE_REQUEST, new RequestScope());// 注册request SCOP
beanFactory.registerScope(WebApplicationContext.SCOPE_SESSION, new SessionScope());// 注册session SCOP
if (sc != null) {
ServletContextScope appScope = new ServletContextScope(sc);
beanFactory.registerScope(WebApplicationContext.SCOPE_APPLICATION, appScope); // 注册application SCOP
// Register as ServletContext attribute, for ContextCleanupListener to detect it.
sc.setAttribute(ServletContextScope.class.getName(), appScope);
}
// 添加依赖项
beanFactory.registerResolvableDependency(ServletRequest.class, new RequestObjectFactory());
beanFactory.registerResolvableDependency(ServletResponse.class, new ResponseObjectFactory());
beanFactory.registerResolvableDependency(HttpSession.class, new SessionObjectFactory());
beanFactory.registerResolvableDependency(WebRequest.class, new WebRequestObjectFactory());
if (jsfPresent) {
FacesDependencyRegistrar.registerFacesDependencies(beanFactory);
}
}