# 内置对象(隐式对象) ## 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) 当前页面的上下文域对象.只在当前页面有效. request域要大于pageContext域对象,因为request可以 请求转发. pageContext可以获取的4个域 . ~~~ 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") %> ~~~ 结果 ``` mike ``` ### 便捷查找 依次从pageConext,request,session,appliction 中查找指定的属性,若找到则立即返回该次查找,若找不到返回null. ~~~ <% session.setAttribute("name", "jack"); request.setAttribute("name", "milan"); application.setAttribute("name", "mike"); %> <%= pageContext.findAttribute("name") %> ~~~