package com.sh.csv.util;

import org.apache.commons.lang3.Validate;

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.

     */

    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.

     */

    @SuppressWarnings("unchecked")

    public static <T> 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.

     */

    public static <T> T getBean(Class<T> 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.

     */

    @Override

    public void setApplicationContext(ApplicationContext 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() {

        Validate.validState(applicationContext != null,

                "applicaitonContext属性未注入, 请在applicationContext.xml中定义SpringContextHolder.");

    }

}