任意位置得到Spring bean
public class org.springframework.web.context.ContextLoaderListener
extends org.springframework.web.context.ContextLoader
implement javax.servlet.ServletContextListener {}
当结合Spring的时候我们首先要在web.xml启动Spring容器，所以会做如下配置：
/** * Obtain the Spring root web application context for the current thread * (i.e. for the current thread's context ClassLoader, which needs to be * the web application's ClassLoader). * @return the current root web application context, or <code>null</code> * if none found * @see org.springframework.web.context.support.SpringBeanAutowiringSupport */public static WebApplicationContext getCurrentWebApplicationContext() {return (WebApplicationContext) currentContextPerThread.get(Thread.currentThread().getContextClassLoader());}