為什么要繼承ApplicationContextAware實現ApplicationContext的這些相關方法，感覺這些方法都在spring中有提供的啊,寫這個SpringUtil.java工具類有什么用?。吭诖a中也沒有看到別的地方有對這個工具類的引用？？代碼如下：import org.springframework.beans.BeansException;import org.springframework.beans.factory.NoSuchBeanDefinitionException;import org.springframework.context.ApplicationContext;import org.springframework.context.ApplicationContextAware; public class SpringContextUtil implements ApplicationContextAware {     private static ApplicationContext applicationContext;     //Spring應用上下文環境          public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {         SpringContextUtil.applicationContext = applicationContext;     }     public static ApplicationContext getApplicationContext() {       return applicationContext;     }         public static Object getBean(String name) throws BeansException {       return applicationContext.getBean(name);     }       public static <T> T getBean(Class<T> requiredType) {       return applicationContext.getBean(requiredType);   }    public static <T> T getBean(String name, Class<T> requiredType) throws BeansException {       return applicationContext.getBean(name, requiredType);     }         public static boolean containsBean(String name) {       return applicationContext.containsBean(name);     }         public static boolean isSingleton(String name) throws NoSuchBeanDefinitionException {       return applicationContext.isSingleton(name);     }     @SuppressWarnings("rawtypes")public static Class getType(String name) throws NoSuchBeanDefinitionException {       return applicationContext.getType(name);     }         public static String[] getAliases(String name) throws NoSuchBeanDefinitionException {       return applicationContext.getAliases(name);     }   }