一直在用的 Spring，你知道它的加載原理嗎？

package com.wokao666;
public class Student {
  private int id;  private String name;  private int age;
  public int getId() {    return id;  }
  public void setId(int id) {    this.id = id;  }
  public String getName() {    return name;  }
  public void setName(String name) {    this.name = name;  }
  public int getAge() {    return age;  }
  public void setAge(int age) {    this.age = age;  }
  public Student(int id, String name, int age) {    super();    this.id = id;    this.name = name;    this.age = age;  }
  public Student() {    super();  }
  @Override  public String toString() {    return "Student [id=" + id + ", ]";  }
}

<bean id="stu1" class="com.wokao666.Student">   <property >property>   <property >property>   <property >property> bean>  <bean id="stu2" class="com.wokao666.Student">   <property >property>   <property >property>   <property >property> bean>

/** * Set the config locations for this application context.//未應用上下文設置資源路徑 * 
If not set, the implementation may use a default as appropriate.//如果未設置，則實現(xiàn)可以根據需要使用默認值。 */public void setConfigLocations(String... locations) {  if (locations != null) {//非空    Assert.noNullElements(locations, "Config locations must not be null");//斷言保證locations的每個元素都不為null    this.configLocations = new String[locations.length];    for (int i = 0; i < locations.length; i++) {      this.configLocations[i] = resolvePath(locations[i]).trim();//去空格，很好奇resolvePath做了什么事情？    }  }  else {    this.configLocations = null;  }}

/** * 解析給定的資源路徑，必要時用相應的環(huán)境屬性值替換占位符，應用于資源路徑配置。 * Resolve the given path, replacing placeholders with corresponding * environment property values if necessary. Applied to config locations. * @param path the original file path * @return the resolved file path * @see org.springframework.core.env.Environment#resolveRequiredPlaceholders(String) */protected String resolvePath(String path) {  return getEnvironment().resolveRequiredPlaceholders(path);}
進入getEnvironment()看看：/** * {@inheritDoc} * 
If {@code null}, a new environment will be initialized via * {@link #createEnvironment()}. */@Overridepublic ConfigurableEnvironment getEnvironment() {  if (this.environment == null) {    this.environment = createEnvironment();  }  return this.environment;}

@Overridepublic void refresh() throws BeansException, IllegalStateException {  synchronized (this.startupShutdownMonitor) {    // 刷新前準備工作，包括設置啟動時間，是否激活標識位，初始化屬性源(property source)配置    prepareRefresh();
    // 創(chuàng)建beanFactory（過程是根據xml為每個bean生成BeanDefinition并注冊到生成的beanFactory    ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
    //準備創(chuàng)建好的beanFactory（給beanFactory設置ClassLoader，設置SpEL表達式解析器，設置類型轉化器【能將xml String類型轉成相應對象】，    //增加內置ApplicationContextAwareProcessor對象，忽略各種Aware對象，注冊各種內置的對賬對象【BeanFactory，ApplicationContext】等，    //注冊AOP相關的一些東西，注冊環(huán)境相關的一些bean    prepareBeanFactory(beanFactory);
    try {      // 模板方法，為容器某些子類擴展功能所用（工廠后處理器）這里可以參考BeanFactoryPostProcessor接口的postProcessBeanFactory方法      postProcessBeanFactory(beanFactory);
      // 調用所有BeanFactoryPostProcessor注冊為Bean      invokeBeanFactoryPostProcessors(beanFactory);
      // 注冊所有實現(xiàn)了BeanPostProcessor接口的Bean      registerBeanPostProcessors(beanFactory);
      // 初始化MessageSource，和國際化相關      initMessageSource();
      // 初始化容器事件傳播器      initApplicationEventMulticaster();
      // 調用容器子類某些特殊Bean的初始化，模板方法      onRefresh();
      // 為事件傳播器注冊監(jiān)聽器      registerListeners();
      // 初始化所有剩余的bean（普通bean）      finishBeanFactoryInitialization(beanFactory);
      // 初始化容器的生命周期事件處理器，并發(fā)布容器的生命周期事件      finishRefresh();    }    catch (BeansException ex) {      if (logger.isWarnEnabled()) {        logger.warn("Exception encountered during context initialization - " +            "cancelling refresh attempt: " + ex);      }      // 銷毀已創(chuàng)建的bean      destroyBeans();      // 重置`active`標志      cancelRefresh(ex);      throw ex;    }    finally {              //重置一些緩存      resetCommonCaches();    }  }}

/** * Prepare this context for refreshing, setting its startup date and * active flag as well as performing any initialization of property sources. */protected void prepareRefresh() {  this.startupDate = System.currentTimeMillis();//設置容器啟動時間  this.closed.set(false);//容器關閉標志，是否關閉？  this.active.set(true);//容器激活標志，是否激活？    if (logger.isInfoEnabled()) {//運行到這里，控制臺就會打印當前容器的信息    logger.info("Refreshing " + this);  }
  // 空方法，由子類覆蓋實現(xiàn)，初始化容器上下文中的property文件  initPropertySources();
  //驗證標記為必需的所有屬性均可解析，請參閱ConfigurablePropertyResolver＃setRequiredProperties  getEnvironment().validateRequiredProperties();
  //允許收集早期的ApplicationEvents，一旦多播器可用，即可發(fā)布...  this.earlyApplicationEvents = new LinkedHashSet();}

三月 22, 2018 4:21:13 下午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@96532d6: startup date [Thu Mar 22 16:21:09 CST 2018]; root of context hierarchy

/** * 告訴子類刷新內部bean工廠(子類是指AbstractApplicationContext的子類，我們使用的是ClassPathXmlApplicationContext) * Tell the subclass to refresh the internal bean factory. */protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {  refreshBeanFactory();//刷新Bean工廠，如果已經存在Bean工廠，那就關閉并銷毀，再創(chuàng)建一個新的bean工廠  ConfigurableListableBeanFactory beanFactory = getBeanFactory();//獲取新創(chuàng)建的Bean工廠  if (logger.isDebugEnabled()) {    logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);//控制臺打印  }  return beanFactory;}
進入refreshBeanFactory()方法：/** * 該實現(xiàn)執(zhí)行該上下文的基礎Bean工廠的實際刷新，關閉以前的Bean工廠（如果有的話）以及為該上下文的生命周期的下一階段初始化新鮮的Bean工廠。 * This implementation performs an actual refresh of this context's underlying * bean factory, shutting down the previous bean factory (if any) and * initializing a fresh bean factory for the next phase of the context's lifecycle. */@Overrideprotected final void refreshBeanFactory() throws BeansException {  if (hasBeanFactory()) {//如果已有bean工廠    destroyBeans();//銷毀    closeBeanFactory();//關閉  }  try {    DefaultListableBeanFactory beanFactory = createBeanFactory();//創(chuàng)建一個新的bean工廠    beanFactory.setSerializationId(getId());//為序列化目的指定一個id，如果需要，可以將此BeanFactory從此id反序列化回BeanFactory對象。    //定制容器，設置啟動參數（bean可覆蓋、循環(huán)引用），開啟注解自動裝配    customizeBeanFactory(beanFactory);    ////將所有BeanDefinition載入beanFactory中，此處依舊是模板方法，具體由子類實現(xiàn)    loadBeanDefinitions(beanFactory);    //beanFactory同步賦值    synchronized (this.beanFactoryMonitor) {      this.beanFactory = beanFactory;    }  }  catch (IOException ex) {    throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);  }}

/** * 使用XmlBeanDefinitionReader來加載beandefnition，之前說過使用reader機制加載Resource資源變?yōu)锽eanDefinition對象 * Loads the bean definitions via an XmlBeanDefinitionReader. * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader * @see #initBeanDefinitionReader * @see #loadBeanDefinitions */@Overrideprotected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {  // 創(chuàng)建XmlBeanDefinitionReader對象  XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
  // 使用當前上下文Enviroment中的Resource配置beanDefinitionReader，因為beanDefinitionReader要將Resource解析成BeanDefinition嘛！  beanDefinitionReader.setEnvironment(this.getEnvironment());  beanDefinitionReader.setResourceLoader(this);  beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
  //初始化這個reader  initBeanDefinitionReader(beanDefinitionReader);  //將beandefinition注冊到工廠中（這一步就是將bean保存到Map中）  loadBeanDefinitions(beanDefinitionReader);}

三月 22, 2018 5:09:40 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions信息: Loading XML bean definitions from class path resource [applicationContext.xml]

//設置bean類加載器//設置Spring語言表達式（SpEL）解析器//掃描ApplicationContextAware bean//注冊類加載期類型切面織入（AOP）LoadTimeWeaver//為各種加載進入beanFactory的bean配置默認環(huán)境