RequestContextListener監聽器用於監聽http請求，每當web應用接收到Http請求，該監聽器就會調用初始化方法，將該請求保存在當前線程的ThreadLocalMap容器中。
public class RequestContextListener implements ServletRequestListener { //其他代碼 @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(); ServletRequestAttributes attributes = new ServletRequestAttributes(request);//請求對象賦值給了attributes 對象的Request屬性
request.setAttribute(REQUEST_ATTRIBUTES_ATTRIBUTE, attributes);
LocaleContextHolder.setLocale(request.getLocale());
RequestContextHolder.setRequestAttributes(attributes);
}
//其他代碼
當前線程的ThreadLocalMap容器存放的key，就是RequestContextHolder類中的靜態ThreadLocal變量requestAttributesHolder：
public abstract class RequestContextHolder { //其他代碼 private static final ThreadLocal<RequestAttributes> requestAttributesHolder = new NamedThreadLocal<RequestAttributes>("Request attributes"); //其他代碼
當請求處理完畢，會調用RequestContextHolder.resetRequestAttributes()方法，清除容器中的請求。
1 public void requestDestroyed(ServletRequestEvent requestEvent) { 2 // 其他代碼 3 4 RequestContextHolder.resetRequestAttributes(); 5 6 7 //其他代碼 8 9 ++++++++++++++++ 10 RequestContextHolder.java{ 11 //其他代碼 12 /** 13 * Reset the RequestAttributes for the current thread. 14 */ 15 public static void resetRequestAttributes() { 16 requestAttributesHolder.remove(); 17 inheritableRequestAttributesHolder.remove(); 18 } 19 //其他代碼