# 內置對象(隱式對象) ## request(HttpServletRequest) ## response(HttpServletResponse) ## out(JspWrite) ## session(HttpSession) ~~~ <% session.setAttribute("name", "jack"); %> <%= session.getAttribute("name") %> ~~~ ## exception(Throwable) ## page(Servlet(this)) ## config(ServletConfig) ## application (ServletContext) ## pageContext(PageContext) 當前頁面的上下文域對象.只在當前頁面有效. request域要大于pageContext域對象,因為request可以 請求轉發. pageContext可以獲取的4個域 . ~~~ public static final int PAGE_SCOPE = 1; public static final int REQUEST_SCOPE = 2; public static final int SESSION_SCOPE = 3; public static final int APPLICATION_SCOPE = 4; ~~~ ~~~ <% session.setAttribute("name", "jack"); pageContext.setAttribute("name", "mike", PageContext.SESSION_SCOPE); //PageContext.SESSION_SCOPE 代表session域 %> <%= session.getAttribute("name") %> ~~~ 結果 ``` mike ``` ### 便捷查找 依次從pageConext,request,session,appliction 中查找指定的屬性,若找到則立即返回該次查找,若找不到返回null. ~~~ <% session.setAttribute("name", "jack"); request.setAttribute("name", "milan"); application.setAttribute("name", "mike"); %> <%= pageContext.findAttribute("name") %> ~~~