SpringContextHolder 静态持有SpringContext的引用

import java.util.Map;

import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

/**
 *
 *以静态变量保存Spring ApplicationContext, 可在任何代码任何地方任何时候中取出ApplicaitonContext.
 * @author zhuh
 */
public class SpringContextHolder implements ApplicationContextAware{

    private static ApplicationContext applicationContext;

    
    //实现ApplicationContextAware接口的context注入函数, 将其存入静态变量.
    public void setApplicationContext(ApplicationContext applicationContext) {
        SpringContextHolder.applicationContext = applicationContext;
    }

   
    //取得存储在静态变量中的ApplicationContext.
    public static ApplicationContext getApplicationContext() {
        checkApplicationContext();
        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) {
        checkApplicationContext();
        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.
    //如果有多个Bean符合Class, 取出第一个.
    @SuppressWarnings("unchecked")
    public static <T> T getBean(Class<T> clazz) {
        checkApplicationContext();
        @SuppressWarnings("rawtypes")
                Map beanMaps = applicationContext.getBeansOfType(clazz);
        if (beanMaps!=null && !beanMaps.isEmpty()) {
            return (T) beanMaps.values().iterator().next();
        } else{
            return null;
        }
    }

    private static void checkApplicationContext() {
        if (applicationContext == null) {
            throw new IllegalStateException("applicaitonContext未注入,请在applicationContext.xml中定义SpringContextHolder");
        }
    }

}