RequestContextListener实现了 ServletRequestListener ,在其覆盖的requestInitialized(ServletRequestEvent requestEvent)方法中,将request最终设置到了RequestContextHolder中.

public class RequestContextListener implements ServletRequestListener {    private static final String REQUEST_ATTRIBUTES_ATTRIBUTE =            RequestContextListener.class.getName() + ".REQUEST_ATTRIBUTES";    @Override    public void requestInitialized(ServletRequestEvent requestEvent) {        if (!(requestEvent.getServletRequest() instanceof HttpServletRequest)) {            throw new IllegalArgumentException(                    "Request is not an HttpServletRequest: " + requestEvent.getServletRequest());        }        HttpServletRequest request = (HttpServletRequest) requestEvent.getServletRequest();//从事件对象中获取request对象        ServletRequestAttributes attributes = new ServletRequestAttributes(request);//将request设置到servletRequestAttributes中        request.setAttribute(REQUEST_ATTRIBUTES_ATTRIBUTE, attributes);//反过来将servletRequestAttributes设置到request中        LocaleContextHolder.setLocale(request.getLocale());        RequestContextHolder.setRequestAttributes(attributes);//再将servletRequestAttributes设置到requestContextHolder中    }

代码中获取该request的步骤:

HttpServletRequest request = ((ServletRequestAttributes) (RequestContextHolder.getRequestAttributes()))                .getRequest();// 返回了RequestAttributes接口,将其强转为ServletRequestAttributes实现类

使用上述方法前,需要先配置RequestContextListener监听器:

             
      
       org.springframework.web.context.request.RequestContextListener