<%@page import="java.util.ArrayList"%> <%@page import="java.util.List"%> <%@page import="com.atguigu.javaweb.Customer"%> <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> <!-- 7. EL 的运算符 --> ${param.score > 60 ? "及格" : "不及格" } <br> <% List<String> names = new ArrayList<String>(); names.add("abc"); request.setAttribute("names", names); %> <!-- empty 可以作用于一个集合, 若该集合不存在或集合中没有元素, 其结果都为 true --> names is empty: ${empty requestScope.names } <br> <!-- 6. 其他隐含对象: pageContext 等(cookie, header, initParam 只需了解.) --> pageContext: pageContext 即为 PageContext 类型, 但只能读取属性就可以一直的 . 下去。 <br> contextPath: ${pageContext.request.contextPath } <br> sessionId: ${pageContext.session.id } <br> sessionAttributeNames: ${pageContext.session.attributeNames } <br> initParam: ${initParam.initName } <br> Accept-Language: ${header["Accept-Language"] } <br> JSESSIONID: ${cookie.JSESSIONID.name } -- ${cookie.JSESSIONID.value } <br> <!-- 5. 与输入有关的隐含对象: param, paramValues --> score: ${param.score } <%-- <%= request.getParameter("score") %> --%> <br> names: ${paramValues.name[0].class.name } <%-- <%= request.getParameterValues("name")[0].getClass().getName() %> --%> <br> <!-- 4. 隐含对象之与范围相关的: pageScope, requestScope, sessionScope, applicationScope --> time: ${applicationScope.time.time } <%-- <%= application.getAttribute("time") %> --%> <br> <!-- 3. EL 可以进行自动的类型转换 --> score: ${param.score + 11} <br> score: <%= request.getParameter("score") + 11 %> <br> <!-- 2. EL 中的隐含对象 --> <% Customer cust2 = new Customer(); cust2.setAge(28); request.setAttribute("customer", cust2); %> age: ${customer.age } <br> <!-- 1. EL 的 . 或 [] 运算符 --> age: ${sessionScope.customer["age"] } <%-- Customer customer = (Customer)session.getAttribute("customer"); out.print(customer.getAge()); --%> <% Customer customer = new Customer(); customer.setName("ATGUIGU"); session.setAttribute("com.atguigu.customer", customer); %> <br> <!-- 如果域对象中的属性名带有特殊字符, 则使用 [] 运算符会很方便. --> name: ${sessionScope["com.atguigu.customer"].name } </body> </html>