在Spring應用中建立全域性獲取ApplicationContext物件

1、需要建立一個類，實現介面ApplicationContextAware的setApplicationContext方法。

2、在建立的這個類中儲存一個靜態的ApplicationContext物件，然後通過靜態的方法返回。

如下，下面是SpringSide的實現，供參考：

/**
 * Copyright (c) 2005-2012 springside.org.cn
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 */
package org.springside.modules.test.spring;

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;

/**
 * 以靜態變數儲存Spring ApplicationContext, 可在任何程式碼任何地方任何時候取出ApplicaitonContext.
 * 
 * @author calvin
 */
public class SpringContextHolder implements ApplicationContextAware, DisposableBean {

    private static ApplicationContext applicationContext = null;

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

    /**
     * 取得儲存在靜態變數中的ApplicationContext.
     */
    public static ApplicationContext getApplicationContext() {
        assertContextInjected();
        return applicationContext;
    }

    /**
     * 從靜態變數applicationContext中取得Bean, 自動轉型為所賦值物件的型別.
     */
    public static <T> T getBean(String name) {
        assertContextInjected();
        return (T) applicationContext.getBean(name);
    }

    /**
     * 從靜態變數applicationContext中取得Bean, 自動轉型為所賦值物件的型別.
     */
    public static <T> T getBean(Class<T> requiredType) {
        assertContextInjected();
        return applicationContext.getBean(requiredType);
    }

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

    /**
     * 實現ApplicationContextAware介面, 注入Context到靜態變數中.
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) {
        logger.debug("注入ApplicationContext到SpringContextHolder:{}", applicationContext);

        if (SpringContextHolder.applicationContext != null) {
            logger.warn("SpringContextHolder中的ApplicationContext被覆蓋, 原有ApplicationContext為:"
                    + SpringContextHolder.applicationContext);
        }

        SpringContextHolder.applicationContext = applicationContext; //NOSONAR
    }

    /**
     * 實現DisposableBean介面, 在Context關閉時清理靜態變數.
     */
    @Override
    public void destroy() throws Exception {
        SpringContextHolder.clearHolder();
    }

    /**
     * 檢查ApplicationContext不為空.
     */
    private static void assertContextInjected() {
        Validate.validState(applicationContext != null,
                "applicaitonContext屬性未注入, 請在applicationContext.xml中定義SpringContextHolder.");
    }
}