private void refreshContext(ConfigurableApplicationContext context) {
  // 由於這裡需要呼叫父類一系列的refresh操作，涉及到了很多核心操作，因此耗時會比較長，本文不做具體展開
    refresh(context);

    // 註冊一個關閉容器時的鉤子函式
    if (this.registerShutdownHook) {
        try {
            context.registerShutdownHook();
        }
        catch (AccessControlException ex) {
            // Not allowed in some environments.
 

        }
    }
}

// 呼叫父類的refresh方法完成容器重新整理的基礎操作
protected void refresh(ApplicationContext applicationContext) {
    Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext);
    ((AbstractApplicationContext)applicationContext).refresh();
}

註冊關閉容器時的鉤子函式的預設實現是在 AbstractApplicationContext 類中：

public void registerShutdownHook() {
  if(this.shutdownHook == null) {
    this.shutdownHook = new Thread() {
      public void run() {
        synchronized(AbstractApplicationContext.this.startupShutdownMonitor) {
          AbstractApplicationContext.this.doClose();
        }
      }
    };
    Runtime.getRuntime().addShutdownHook(this
 
.shutdownHook);
  }
}

如果沒有提供自定義的shutdownHook，那麼會生成一個預設的，並新增到Runtime中。預設行為就是呼叫它的doClose方法，完成一些容器銷燬時的清理工作。

3.2.6 Spring Context後置處理

protected void afterRefresh(ConfigurableApplicationContext context,
            ApplicationArguments args) {
    callRunners(context, args);
}

private void callRunners(ApplicationContext context, ApplicationArguments args) {
    List<Object> runners = new ArrayList<Object>();
    runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
    runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
    AnnotationAwareOrderComparator.sort(runners);
    for (Object runner : new LinkedHashSet<Object>(runners)) {
        if (runner instanceof ApplicationRunner) {
            callRunner((ApplicationRunner) runner, args);
        }
        if (runner instanceof CommandLineRunner) {
            callRunner((CommandLineRunner) runner, args);
        }
    }
}

private void callRunner(ApplicationRunner runner, ApplicationArguments args) {
    try {
        (runner).run(args);
    }
    catch (Exception ex) {
        throw new IllegalStateException("Failed to execute ApplicationRunner", ex);
    }
}

private void callRunner(CommandLineRunner runner, ApplicationArguments args) {
    try {
        (runner).run(args.getSourceArgs());
    }
    catch (Exception ex) {
        throw new IllegalStateException("Failed to execute CommandLineRunner", ex);
    }
}

所謂的後置操作，就是在容器完成重新整理後，依次呼叫註冊的Runners。Runners可以是兩個介面的實現類：

• org.springframework.boot.ApplicationRunner
• org.springframework.boot.CommandLineRunner

CommandLineRunner、ApplicationRunner 介面是在容器啟動成功後的最後一步回撥（類似開機自啟動）

這兩個介面有什麼區別呢：

public interface ApplicationRunner {

    void run(ApplicationArguments args) throws Exception;

}

public interface CommandLineRunner {

    void run(String... args) throws Exception;

}

其實沒有什麼不同之處，除了介面中的run方法接受的引數型別是不一樣的以外。一個是封裝好的 ApplicationArguments 型別，另一個是直接的String不定長陣列型別。因此根據需要選擇相應的介面實現即可。