EL表达式的11隐含对象

EL表达式在不同范围如何取值：

<%pageContext.setAttribute("book", "红楼梦");request.setAttribute("book", "水浒传");session.setAttribute("book", "三国演义");application.setAttribute("book", "西游记");%><!-- 当key值相同的时候，并且没有指明在什么范围内取值的话，会取最小范围内的值返回 -->${book }<br/><!-- 获取不同范围内的值 -->pageScope:${pageScope.book }<br />requestScope:${requestScope.book }<br />sessionScope:${sessionScope.book }<br />applicationScope:${applicationScope.book }<br /><hr/><input type="text" value = "${pageScope.book }" /><input type="text" value = "${pageScope['book']}" /><input type = "text" value = "<%=request.getParameter("user_id")==null?"":request.getParameter("user_id") %>"  /><br/>param:相当于request.getParameter("user_id"); <input type= "text" value = "${param.user_id }" /><br/>paramValues(一key多值):相当于request.getParameterValues("user_id");<input type = "text" value= "${paramValues }" />