Spring refresh()原始碼解析

2023-03-15 06:01:17

正文

public void refresh() throws BeansException, IllegalStateException {
    synchronized(this.startupShutdownMonitor) {
        // 1. 初始化前的預處理
        this.prepareRefresh();
        // 2. 重新整理Bean工廠
        ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
        // 3. BeanFactory的預處理設定
        this.prepareBeanFactory(beanFactory);
        try {
            // 4. BeanFactory的後置處理
            this.postProcessBeanFactory(beanFactory);
            // 5. 執行BeanFactory後置處理器
            this.invokeBeanFactoryPostProcessors(beanFactory);
            // 6. 註冊Bean的後置處理器
            this.registerBeanPostProcessors(beanFactory);
            // 7. 初始化MessageSource
            this.initMessageSource();
            // 8. 初始化事件派發器
            this.initApplicationEventMulticaster();
            // 9. 子類的多型onRefresh
            this.onRefresh();
            // 10. 註冊監聽器
            this.registerListeners();
            // 11. 初始化所有剩下的單例Bean
            this.finishBeanFactoryInitialization(beanFactory);
            // 12. 完成容器的建立工作
            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. 清除快取
            this.resetCommonCaches();
        }
    }
}

一、prepareRefresh：初始化前的預處理

protected void prepareRefresh() {
    //設定容器啟動時間
    this.startupDate = System.currentTimeMillis();
    //設定容器關閉狀態為false
    this.closed.set(false);
    //設定容器啟用狀態為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初始化屬性資源
    this.initPropertySources();
    //1.2校驗
    this.getEnvironment().validateRequiredProperties();
    this.earlyApplicationEvents = new LinkedHashSet();
}

1.1初始化屬性值

初始化方法是個模壓方法，由子類重寫

protected void initPropertySources() {
}

Web容器GenericWebApplicationContext重寫了此方法

protected void initPropertySources() {
    //獲取環境資訊
   ConfigurableEnvironment env = getEnvironment();
   //判斷是否是web設定環境
   if (env instanceof ConfigurableWebEnvironment) {
      ((ConfigurableWebEnvironment) env).initPropertySources(this.servletContext, null);
   }
}

最終由StandardServletEnvironment進行初始化

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 的一些初始化引數放入IOC容器中

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屬性校驗

通過預留位置解析器校驗資源集合

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

這裡的解析器作為常數在環境被範例化時就被建立出來的，PropertySourcesPropertyResolver是預留位置解析器，將資料來源中預留位置替換成目標值

校驗是否有需要被預留位置修飾的屬性，如果有但是資源中找不到對應屬性的key就會丟擲異常

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： 資原始檔

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

測試程式碼

    @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}"));  //輸出must be encoding gbk
    }

輸出結果

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

二、obtainFreshBeanFactory：重新整理Bean工廠

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
   //2.1重新整理Bean工廠
   refreshBeanFactory();
   return getBeanFactory();
}

將容器重新整理標識改為true，並且設定了工廠序列化id

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工廠預處理

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
   // 設定BeanFactory的類載入器、表示式解析器等
   beanFactory.setBeanClassLoader(getClassLoader());
   beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
   beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
   // 3.1 新增Aware執行器
   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 自動注入的支援
   beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
   beanFactory.registerResolvableDependency(ResourceLoader.class, this);
   beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
   beanFactory.registerResolvableDependency(ApplicationContext.class, this);
   // 3.3 新增監聽器執行器
   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執行器

ApplicationContextDProcessor實現了BeanPostProcessor的postProcessBeforeInitialization介面，在所有Bean初始化前會執行當前方法

public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
   //判斷Bean是Aware的子類
   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&lt;Object&gt;) () -&gt; {
         invokeAwareInterfaces(bean);
         return null;
      }, acc);
   }
   else {
       //回撥執行Aware介面
      invokeAwareInterfaces(bean);
   }
   return bean;
}

如果當前Bean是Aware的子類，那麼將Bean強轉成Aware型別，通過回撥將資訊設定到Bean中

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：自動注入的支援

如果過容器中有多個相同介面的實現類，那麼在自動注入的時候會注入註冊的實現類

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

3.3 新增監聽器執行器

ApplicationListenerDetector主要作用是新增和銷燬監聽器,實現了BeanPostProcessor的postProcessAfterInitialization（Bean範例化之後）方法和DestructionAwareBeanPostProcessor的postProcessBeforeDestruction（Bean銷燬之前）方法

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

四、BeanFactory的後置處理

這是個模壓方法,由子類AnnotationConfigServletWebServerApplicationContext實現

protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
}

AnnotationConfigServletWebServerApplicationContext首先調了父類別 ServletWebServerApplicationContext 的 postProcessBeanFactory 方法

protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
   //4.1後置處理Bean工廠
   super.postProcessBeanFactory(beanFactory);
   if (this.basePackages != null && this.basePackages.length > 0) {
      //basePackages為空不會執行
      this.scanner.scan(this.basePackages);
   }
   if (!this.annotatedClasses.isEmpty()) {
      this.reader.register(ClassUtils.toClassArray(this.annotatedClasses));
   }
}

4.1 後置處理bean工廠

父類別ServletWebServerApplicationContext首先向Bean工廠中注入了一個執行器

protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
   //4.1.1注入執行器
   beanFactory.addBeanPostProcessor(new WebApplicationContextServletContextAwareProcessor(this));
   beanFactory.ignoreDependencyInterface(ServletContextAware.class);
   //4.1.2註冊作用域
   registerWebApplicationScopes();
}

4.1.1 WebApplicationContextServletContextAwareProcessor

WebApplicationContextServletContextAwareProcessor繼承了ServletContextAwareProcessor

ServletContextAwareProcessor繼承了BeanPostProcessor實現了postProcessBeforeInitialization（Bean初始化前執行）

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 註冊web的應用域

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

ExistingWebApplicationScopes是ServletWebServerApplicationContext類中的一個靜態類

原始碼如下：

    public static class ExistingWebApplicationScopes {
        static {
         Set<String> scopes = new LinkedHashSet<>();
         scopes.add(WebApplicationContext.SCOPE_REQUEST);
         scopes.add(WebApplicationContext.SCOPE_SESSION);
         SCOPES = Collections.unmodifiableSet(scopes);
      }
        // 這是構造方法，大概就是根據SCOPES獲取beanFactory中已經註冊的scope，然後放入scopes
        // 需要注意的是，在上面的方法中，第二行才在向beanFactory中註冊，也就是這時的beanFactory裡面沒有request和session這兩個scop
        // 所以這裡就完成了beanFactory的賦值。建議打斷點進去看看
      public ExistingWebApplicationScopes(ConfigurableListableBeanFactory beanFactory) {
         this.beanFactory = beanFactory;
         for (String scopeName : SCOPES) {
            Scope scope = beanFactory.getRegisteredScope(scopeName);
            if (scope != null) {
               this.scopes.put(scopeName, scope);
            }
         }
      }
        // 由於上面的方法並沒有值存入scopes，所以這裡也就沒執行裡面的內容
      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()，這個方法就是向beanFactory註冊web的scope了，原始碼如下

    public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory) {
      registerWebApplicationScopes(beanFactory, null);
   }
    public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory,
         @Nullable ServletContext sc) {
        // 註冊作用域
      beanFactory.registerScope(WebApplicationContext.SCOPE_REQUEST, new RequestScope());// 註冊request  SCOP
      beanFactory.registerScope(WebApplicationContext.SCOPE_SESSION, new SessionScope());// 註冊session SCOP
      if (sc != null) {
         ServletContextScope appScope = new ServletContextScope(sc);
         beanFactory.registerScope(WebApplicationContext.SCOPE_APPLICATION, appScope); // 註冊application SCOP
         // Register as ServletContext attribute, for ContextCleanupListener to detect it.
         sc.setAttribute(ServletContextScope.class.getName(), appScope);
      }
        // 新增依賴項
      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);
      }
   }

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