EL et JSTL
Un, le code
1. Code
package com.web;
import com.c3p0.pojo.User;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
@WebServlet("/as")
public class AServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
User user = new User("tom","123");
User user2 = new User("tom2","222");
User user3 = new User("tom","333");
User[] arr={
user,user2,user3};
ArrayList<User> list = new ArrayList<>();
list.add(user);
list.add(user2);
list.add(user3);
//数组和集合,存进域中
request.setAttribute("arr",arr);
request.setAttribute("list",list);
//转发到jsp
request.getRequestDispatcher("/jstl/b.jsp").forward(request,response);
}
}
<%@ page import="java.util.ArrayList" %><%--
Created by IntelliJ IDEA.
User: admin
Date: 2021/1/28
Time: 9:59
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<%--定义用户类和猫类,用户中将猫作为成员变量--%>
<%!
public class User {
String name;
int age;
Cat cat;
public String getName2() {
return name;
}
public int getAge() {
return age;
}
public Cat getCat() {
return cat;
}
}
public class Cat{
String name;
int age;
public String getName() {
return name;
}
public int getAge() {
return age;
}
}
%>
<%
//有2个人,每人养了一只猫.存进list集合,使用EL取出展示
User user1 = new User();
User user2 = new User();
Cat cat1 = new Cat();
Cat cat2 = new Cat();
user1.cat=cat1;
user2.cat=cat2;
//张三 的猫的名字叫加肥 2岁
user1.name="张三";
cat1.name="加肥";
cat1.age=2;
//存进list集合
ArrayList<User> users = new ArrayList<>();
users.add(user1);
users.add(user2);
//集合存进域中
pageContext.setAttribute("users",users);
%>
<%--获得的是get方法里面的值--%>
${
pageScope.users[0].name2}的猫的名字叫
${
pageScope.users[0].cat.name},${
pageScope.users[0].cat.age}岁
</body>
</html>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<%--
动态获取虚拟路径
--%>
${
pageContext.request.contextPath}
<%--param就相当于 request.getParameter() 可以获取请求参数--%>
${
param.age}
${
param.sex}
<hr>
${
cookie.JSESSION.name}------${
cookie.JSESSION.value}<br>
${
cookie['Webstorm-59a98a54'].name}---${
cookie['Webstorm-59a98a54'].value}
<%--cookie可以获取每个cookie的值--%>
</body>
</html>
<%@ page import="java.util.Map" %>
<%@ page import="java.util.HashMap" %><%--
Created by IntelliJ IDEA.
User: admin
Date: 2021/1/28
Time: 10:40
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<%!
public class City{
String name;
int man;
int money;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getMan() {
return man;
}
public void setMan(int man) {
this.man = man;
}
public int getMoney() {
return money;
}
public void setMoney(int money) {
this.money = money;
}
}
%>
<%
City city1 = new City();
City city2 = new City();
city1.setName("徐州");;
city1.setMan(80);
city1.setMoney(30);
city2.setName("关羽");;
city2.setMan(100);
city2.setMoney(40);
HashMap<String, City> map = new HashMap<String,City>();
map.put("张飞",city1);
map.put("关羽",city2);
pageContext.setAttribute("map",map);
%>
<%--输出：张飞守得徐州城,有80万人,粮草30万石,关羽守的荆州城,有100万人，粮草40万石--%>
张飞守的${
pageScope.map.张飞.name}城,有${
pageScope.map.['张飞'].man}万人,粮草${
pageScope.map.get("张飞").money}万石
<hr>
${
"张飞守的".concat(pageScope.map.张飞.name).concat("城,有").concat(pageScope.map['张飞'].man).concat("万人,粮草")
.concat(pageScope.map.get("张飞").money).concat("万石")}
</body>
</html>
<%--
Created by IntelliJ IDEA.
User: admin
Date: 2021/1/28
Time: 15:24
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<%--单个条件判断--%>
<c:if test="${not empty 'list'}">
list不为空
</c:if>
<%--多个条件判断--%>
<%
request.setAttribute("m",1);
%>
<c:set var="m" value="7" scope="request"/>
<hr>
<c:choose>
<c:when test="${m>=1 && m<=3}">
<h3>spring</h3>
</c:when>
<c:when test="${m>=4 && m<=6}">
<h3>spring</h3>
</c:when>
<c:when test="${m>=7 && m<=9}">
<h3>spring</h3>
</c:when>
<c:otherwise>
<h3>winter</h3>
</c:otherwise>
</c:choose>
</body>
</html>
<%--
Created by IntelliJ IDEA.
User: admin
Date: 2021/1/28
Time: 15:38
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<%--输出5次hello--%>
<%--
var="i" i存在最小域pageContext中
--%>
<c:forEach begin="1" end="5" step="2" var="i" varStatus="vs">
${
i}--${
vs.index}--${
vs.count} <br>
</c:forEach>
<hr>
<%--
增强for循环
for(int a:arr)
--%>
<%--增强for--%>
<c:forEach var="u" items="${list}">
${
u.name}--${
u.psw} <br>
</c:forEach>
</body>
</html>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<table border="1" cellpadding="15" cellspacing="0">
<tr>
<th>编号</th>
<th>姓名</th>
<th>年龄</th>
<th>工资</th>
<th>功能</th>
</tr>
<c:forEach var="e" items="${list}">
<tr>
<td>${
e.id}</td>
<td>${
e.name}</td>
<td>${
e.age}</td>
<td>${
e.money}</td>
<td><input type="button" value="增加">
<input type="button" value="删除">
<input type="button" value="修改"></td>
</tr>
</c:forEach>
</table>
</body>
</html>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<%
//request.getRequestDispatcher("/2.el.jsp?age=666").forward(request,response);
%>
${
pageContext.request.getRequestDispatcher("/2.el.jsp?age=888").forward(pageContext.request,pageContext.response)}
<%--
jsp动作
--%>
<jsp:forward page="/el/2.el.jsp?age=111">
<jsp:param name="sex" value="aa"/>
</jsp:forward>
</body>
</html>
Pour résumer
Ce qui précède est la méthode et tout le code lié à el et jstl.