Spring源码关于RequestContext相关信息获取 事件监听器的相关代码实现

public class RequestContextListener implements ServletRequestListener {    private static final String REQUEST_ATTRIBUTES_ATTRIBUTE = RequestContextListener.class            .getName() + ".REQUEST_ATTRIBUTES";    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();        ServletRequestAttributes attributes = new ServletRequestAttributes(                request);        request.setAttribute(REQUEST_ATTRIBUTES_ATTRIBUTE, attributes);        LocaleContextHolder.setLocale(request.getLocale());        RequestContextHolder.setRequestAttributes(attributes);    }    public void requestDestroyed(ServletRequestEvent requestEvent) {        ServletRequestAttributes attributes = null;        Object reqAttr = requestEvent.getServletRequest().getAttribute(                REQUEST_ATTRIBUTES_ATTRIBUTE);        if (reqAttr instanceof ServletRequestAttributes) {            attributes = (ServletRequestAttributes) reqAttr;        }        RequestAttributes threadAttributes = RequestContextHolder                .getRequestAttributes();        if (threadAttributes != null) {            LocaleContextHolder.resetLocaleContext();            RequestContextHolder.resetRequestAttributes();            if ((attributes == null)                    && (threadAttributes instanceof ServletRequestAttributes)) {                attributes = (ServletRequestAttributes) threadAttributes;            }        }        if (attributes != null)            attributes.requestCompleted();    }}public abstract interface ServletRequestListener extends EventListener {    public abstract void requestDestroyed(            ServletRequestEvent paramServletRequestEvent);    public abstract void requestInitialized(            ServletRequestEvent paramServletRequestEvent);}public interface EventListener {}public class ServletRequestEvent extends EventObject {    private static final long serialVersionUID = 1L;    private final transient ServletRequest request;    public ServletRequestEvent(ServletContext sc, ServletRequest request) {        super(sc);        this.request = request;    }    public ServletRequest getServletRequest() {        return this.request;    }    public ServletContext getServletContext() {        return ((ServletContext) super.getSource());    }}public class EventObject implements java.io.Serializable {    private static final long serialVersionUID = 5516075349620653480L;    /**     * The object on which the Event initially occurred.     */    protected transient Object  source;    /**     * Constructs a prototypical Event.     *     * @param    source    The object on which the Event initially occurred.     * @exception  IllegalArgumentException  if source is null.     */    public EventObject(Object source) {        if (source == null)            throw new IllegalArgumentException("null source");        this.source = source;    }    /**     * The object on which the Event initially occurred.     *     * @return   The object on which the Event initially occurred.     */    public Object getSource() {        return source;    }    /**     * Returns a String representation of this EventObject.     *     * @return  A a String representation of this EventObject.     */    public String toString() {        return getClass().getName() + "[source=" + source + "]";    }}