配置springmvc在其他类中（spring容器外）获取注入bean

学习https://github.com/thinkgem/jeesite

今天在写JedisUtils的时候要注入JedisPool，而这个属性被设置为static，@Resource和@Autowired都不可以注入，因为spring不能为静态变量依赖注入。因此需要额外的方法获取spring管理的bean。本文即SpringContextHolder：

package com.demo.common.utils;

import org.apache.commons.lang3.Validate;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeansException;
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.
 * Created by Administrator on 2016/2/23.
 */
@Service
@Lazy(false)
public class SpringContextHolder implements ApplicationContextAware ,DisposableBean {
    private static ApplicationContext applicationContext = null;
    private static Logger logger = LoggerFactory.getLogger(SpringContextHolder.class);

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

    /**
     * 从静态变量applicationContext中去的Bean，自动转型为所复制对象的类型
     * @param name
     * @param <T>
     * @return
     */
    public static <T> T getBean(String name){
        assertContextInjected();
        return (T)applicationContext.getBean(name);
    }

    /**
     * 从静态变量applicationContext中去的Bean，自动转型为所复制对象的类型
     * @param requiredType
     * @param <T>
     * @return
     */
    public static <T> T getBean(Class<T> requiredType){
        assertContextInjected();
        return (T)applicationContext.getBean(requiredType);
    }

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


    /**
     * 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.");
    }

    /**
     * 实现ApplicationContextAware接口，注入Context到静态变量
     * @param applicationContext
     * @throws BeansException
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        SpringContextHolder.applicationContext = applicationContext;
    }

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