Spring通过ApplicationContext主动获取bean的方法讲解

/**
 * spring上下文配置
 * @author Mingchenchen
 *
 */
@Component
public class SpringContextUtil implements ApplicationContextAware {
  private static Logger logger = Logger.getLogger(SpringContextUtil.class);
  private static ApplicationContext applicationContext = null;
  public void setApplicationContext(ApplicationContext applicationContext) throws BeansException
  {
    logger.info("------SpringContextUtil setApplicationContext-------");
    SpringContextUtil.applicationContext = applicationContext;
  }
  public static ApplicationContext getApplicationContext() {
    return applicationContext;
  }
  /**
   * 注意 bean name默认 = 类名(首字母小写)
   * 例如: A8sClusterDao = getBean("k8sClusterDao")
   * @param name
   * @return
   * @throws BeansException
   */
  public static Object getBean(String name) throws BeansException {
    return applicationContext.getBean(name);
  }
  /**
   * 根据类名获取到bean
   * @param <T>
   * @param clazz
   * @return
   * @throws BeansException
   */
  @SuppressWarnings("unchecked")
  public static <T> T getBeanByName(Class<T> clazz) throws BeansException {
    try {
      char[] cs=clazz.getSimpleName().toCharArray();
      cs[0] += 32;//首字母大写到小写
      return (T) applicationContext.getBean(String.valueOf(cs));
    } catch (Exception e) {
      e.printStackTrace();
      return null;
    } 
  }
  public static boolean containsBean(String name) {
    return applicationContext.containsBean(name);
  }
  public static boolean isSingleton(String name) throws NoSuchBeanDefinitionException {
    return applicationContext.isSingleton(name);
  }
}

<!-- 初始化Spring容器，让Spring容器随Web应用的启动而自动启动 --> 
  <listener> 
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> 
  </listener> 

/**
 * spring上下文配置
 * @author Mingchenchen
 *
 */
public class SpringContextUtil {
  private static Logger logger = Logger.getLogger(SpringContextUtil.class);
  //@Autowired 沿用springTest的这种方法 是否会更好？
  //ApplicationContext ctx;
  private static ApplicationContext applicationContext = null;
  public static void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    logger.info("------SpringContextUtil setApplicationContext-------");
    SpringContextUtil.applicationContext = applicationContext;
  }
  //注意此处变成了static
  public static ApplicationContext getApplicationContext() {
    return applicationContext;
  }
  /**
   * 注意 bean name默认 = 类名(首字母小写)
   * 例如: A8sClusterDao = getBean("k8sClusterDao")
   * @param name
   * @return
   * @throws BeansException
   */
  public static Object getBean(String name) throws BeansException {
    return applicationContext.getBean(name);
  }
  /**
   * 根据类名获取到bean
   * @param <T>
   * @param clazz
   * @return
   * @throws BeansException
   */
  @SuppressWarnings("unchecked")
  public static <T> T getBeanByName(Class<T> clazz) throws BeansException {
    try {
      char[] cs=clazz.getSimpleName().toCharArray();
      cs[0] += 32;//首字母大写到小写
      return (T) applicationContext.getBean(String.valueOf(cs));
    } catch (Exception e) {
      e.printStackTrace();
      return null;
    } 
  }
  public static boolean containsBean(String name) {
    return applicationContext.containsBean(name);
  }
  public static boolean isSingleton(String name) throws NoSuchBeanDefinitionException {
    return applicationContext.isSingleton(name);
  }
}
/**
 * Descripties: 系统初始化
 * @author wangkaiping
 * 2016年5月23日 上午11:58:09
 */
@Component
public class SystemInit implements InitializingBean,ApplicationContextAware{
  private static Logger logger = Logger.getLogger(SystemInit.class);
  @Autowired
  private ClusterDao clusterDao;
  @Override
  public void afterPropertiesSet() throws Exception {
    logger.info("--------------系统初始化中-------------------");
    initClusterCache();//初始化集群数据 必须最开始完成
    initRefreshAppStatusTask();
    initUpdateAppStatusToDB();
    initUpdateSession();
    logger.info("--------------系统初始化完成-------------------");
  }
  /**
   * 1.初始化集群数据
   */
  private void initClusterCache(){
    logger.info("1.初始化集群信息到缓存中:ClusterCache开始");
    //查询数据库所有的集群数据
    List<ClusterEntity> allClusterInfoList = clusterDao.selectAll(ClusterEntity.class, "delete_flag=0");
    for (ClusterEntity k8sClusterEntity : allClusterInfoList) {
      ClusterCache.put(k8sClusterEntity.getUuid() , k8sClusterEntity);//存入缓存
    }
    logger.info("1.初始化集群信息到缓存中:ClusterCache完成,总共" + allClusterInfoList.size() + "条数据");
  }
  /**
   * 2.初始化异步任务:刷新所有应用状态
   */
  private void initRefreshAppStatusTask() {
    logger.info("2.初始化任务:RefreshAllAppStatusTask 刷新应用下的k8s的pod状态并存入待更新队列");
    RefreshAppStatusExcutor.init();
    logger.info("2.初始化任务:RefreshAllAppStatusTask 完成");
  }
  /**
   * 3.初始化异步任务:更新状态到数据库
   */
  private void initUpdateAppStatusToDB() {
    logger.info("3.初始化任务:RefreshToDBTask 从待更新Appinstance队列取出数据并更新数据库");
    UpdateAppStatusToDBExcutor.init();
    logger.info("3.初始化任务:RefreshToDBTask 完成");
  }
  /**
   * 4. 初始化异步任务： 更新用户的所有session
   */
  private void initUpdateSession() {
    logger.info("4.初始化任务：更新session开始");
    UserSessionUpdateExcutor.init();
    logger.info("4.初始化任务：更新session结束");
  }
  ////////////////////////////////////////////////////////////////
  //此方法一定不要写成static
  @Override
  public void setApplicationContext(ApplicationContext applicationContext) 
                        throws BeansException {
    //实际上是把applicationContext传入到了SpringContextUtil里面
    SpringContextUtil.setApplicationContext(applicationContext);
  }
}