JSP EL表示式
阿新 • • 發佈：2022-04-21
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <%-- EL表示式 預設值空 不是null 操作域物件中的資料 不能區域性變數 從小到大去找--%> <% //設定資料 pageContext.setAttribute("name1","pageC"); request.setAttribute("name2","req"); session.setAttribute("name3","sess"); application.setAttribute("name4","app"); %> <%-- 獲取資料--%> ${"name"} <%-- 獲取指定範圍--%> ${pageScope.name1} ${requestScope.name2} ${sessionScope.name3} ${applicationScope.name4} </body> </html>
<%@ page import="java.util.List" %> <%@ page import="java.util.ArrayList" %> <%@ page import="java.util.Map" %> <%@ page import="java.util.HashMap" %> <%@ page import="bean.User" %> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <% List<String> list=new ArrayList<>(); list.add("aaa"); list.add("bbb"); request.setAttribute("list",list); Map map=new HashMap(); map.put("bbb",111); request.setAttribute("map",map); //JavaBean 必須提供get方法 User user=new User("String"); request.setAttribute("user",user); %> <%-- 獲取集合值--%> ${list.size()}<br> ${list[1]}<br> ${map.bbb}<br> ${map[bbb]}<br> <%--javabean--%> ${user}<br> ${user.name}<br> ${user.getName()} </body> </html>
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <% request.setAttribute("str1",""); request.setAttribute("str2","str2"); request.setAttribute("str3",null); %> <%-- empty 判斷域物件是否為空 有值為false 空 null都為true --%> ${empty str1}<br> ${empty str3}<br> ${empty str2}<br> ${empty str4}<br> </body> </html>