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package com.github.ibole.infrastructure.common.spring;

import static com.google.common.base.Preconditions.checkArgument;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.annotation.Lazy;
import org.springframework.stereotype.Service;


/**
 * 以静态变量保存Spring ApplicationContext, 可在任何代码任何地方任何时候取出ApplicaitonContext.
 * 
 */
@Service
@Lazy(false)
public class SpringContextHolder implements ApplicationContextAware, DisposableBean {

  private static ApplicationContext applicationContext = null;

  private static Logger logger = LoggerFactory.getLogger(SpringContextHolder.class);

  /**
   * 取得存储在静态变量中的ApplicationContext.
   * @return applicationContext ApplicationContext
   */
  public static ApplicationContext getApplicationContext() {
    assertContextInjected();
    return applicationContext;
  }

  /**
   * 从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
   * @param  T bean type
   * @param name String
   * @return instance of the bean
   */
  @SuppressWarnings("unchecked")
  public static  T getBean(String name) {
    assertContextInjected();
    return (T) applicationContext.getBean(name);
  }

  /**
   * 从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
   * @param  T bean type
   * @param requiredType Class
   * @return bean instance
   */
  public static  T getBean(Class requiredType) {
    assertContextInjected();
    return applicationContext.getBean(requiredType);
  }

  /**
   * 清除SpringContextHolder中的ApplicationContext为Null.
   */
  public static void clearHolder() {
    if (logger.isDebugEnabled()) {
      logger.debug("清除SpringContextHolder中的ApplicationContext:" + applicationContext);
    }
    applicationContext = null;
  }

  /**
   * 实现ApplicationContextAware接口, 注入Context到静态变量中.
   * @param applicationContext ApplicationContext
   */
  @Override
  public void setApplicationContext(ApplicationContext applicationContext) {
    logger.debug("注入ApplicationContext到SpringContextHolder:{}", applicationContext);
    if (SpringContextHolder.applicationContext != null) {
      logger.info("SpringContextHolder中的ApplicationContext被覆盖, 原有ApplicationContext为:"
          + SpringContextHolder.applicationContext);
    }
    SpringContextHolder.applicationContext = applicationContext;
  }

  /**
   * 实现DisposableBean接口, 在Context关闭时清理静态变量.
   */
  @Override
  public void destroy() throws Exception {
    SpringContextHolder.clearHolder();
  }

  /**
   * 检查ApplicationContext不为空.
   */
  private static void assertContextInjected() {
    checkArgument(applicationContext != null,
        "applicaitonContext属性未注入, 请在applicationContext.xml中定义SpringContextHolder.");
  }
}