el表达式和jstl相关案例_使用el和jstl实现一个类-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_45220351/article/details/110007401

//需求-输出Person类中的普通属性，数组属性，list集合属性和map集合属性
1.创建person类

import java.util.Arrays;
import java.util.List;
import java.util.Map;

public class Person {
    //需求-输出Person类中的普通属性，数组属性，list集合属性和map集合属性。
    private String  name;
    private String[] phone;
    private List<String> cities;
    private Map<String,Object> map;

    @Override
    public String toString() {
        return "Person{" +
                "name=" + name +
                ", phone=" + Arrays.toString(phone) +
                ", cities=" + cities +
                ", map=" + map +
                '}';
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String[] getPhone() {
        return phone;
    }

    public void setPhone(String[] phone) {
        this.phone = phone;
    }

    public List<String> getCities() {
        return cities;
    }

    public void setCities(List<String> cities) {
        this.cities = cities;
    }

    public Map<String, Object> getMap() {
        return map;
    }

    public void setMap(Map<String, Object> map) {
        this.map = map;
    }
}

2.创建jsp文件

<%@ page import="com.atshangqiu.com.Person" %>
<%@ page import="java.util.List" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.Map" %>
<%@ page import="java.util.HashMap" %>

<%--
  Created by IntelliJ IDEA.
  User: lenovo
  Date: 2020/11/21
  Time: 20:57
  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>
<%
    Person p=new Person();
    p.setName("chenbin");
    p.setPhone(new String[]{"1272772","12312312"});
    List<String> cities=new ArrayList<String>();
    cities.add("北京");
    cities.add("阿萨德");
    p.setCities(cities);
    Map map=new HashMap();
    map.put("key1","value1");
    map.put("key2","value2");
    p.setMap(map);
    pageContext.setAttribute("person",p);
%>
输出person：${person}<br/>
输出person的name属性${person.name}
输出person的pones数组的属性值：${person.phone[0]}
输出person的cities集合的元素值：${person.cities}
输出person的list集合中个别元素值:${person.cities[0]}
输出person的map集合:${person.map}
输出person的map集合:${person.map.key1}
${pageScope.person }
</body>
</html>

3。<c:set/>，<c:if/>，<c:foreach/>相关案例
student类

public class Student {
    //编号，用户名，密码，年龄，电话信息
    private Integer id;
    private String username;
    private String password;
    private Integer age;
    private String phone;

    public Student(Integer id, String username, String password, Integer age, String phone) {
        this.id = id;
        this.username = username;
        this.password = password;
        this.age = age;
        this.phone = phone;
    }

    public Student() {
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", age=" + age +
                ", phone='" + phone + '\'' +
                '}';
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }
}

jsp文件

<%@ page import="java.util.Map" %>
<%@ page import="java.util.HashMap" %>
<%@ page import="java.util.List" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="com.atshangqiu.com.Student" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%--
  Created by IntelliJ IDEA.
  User: lenovo
  Date: 2020/11/22
  Time: 16:05
  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>
<%--
<c:set/>作用：set标签可以往域中保存数据
域对象.setAttribute(key,value);
保存到哪个域
scope属性设置保存到哪个域
page表示pagecontext域
request表示request域
session表示session域
application表示servletcontext域
var属性是设置key是多少
value属性设置value是多少
--%>
保存之前：${requestScope.abc}
<c:set scope="request" var="abc" value="abcvalue"></c:set>
保存之后：${requestScope.abc}
<%--
if标签用来做if判断
<c:if/>
test属性表示判断的条件（使用el表达式输出）
--%>
<c:if test="${12==12}">
    <h1>qwewq</h1>
</c:if>
<%--
<c:choose><c:when><c:otherwise>标签
作用：多路判断。跟switch...case...default非常接近
--%>
<%
    request.setAttribute("height",178);
    pageContext.setAttribute("zhong",156);
%>
<%--
choose标签开始选择判断
when标签表示每一种判断情况
test属性表示当前这种判断情况的值
otherwise表示剩下的情况
注意点:1.不能使用html注释，要使用jsp注释
2.when标签的父标签一定是choose标签
--%>
<c:choose>
<c:when test="${requestScope.height>190}">
    <h1>巨人</h1>
</c:when>
    <c:when test="${requestScope.height>180}">
        <h1>很高</h1>
    </c:when>
    <c:when test="${requestScope.height>170}">
        <h1>有点高</h1>
    </c:when>
    <c:otherwise>
        <h1>剩下的小于170</h1>
    </c:otherwise>
</c:choose>
<%--
<c:foreach/>
遍历  1到10，输出
begin属性设置开始的索引
end属性设置结束的索引
var属性表示循环的变量
--%>
<table border="1">
    <c:forEach begin="1" end="10" var="i">
        <tr>
                <td>${i}</td>
        </tr>
    </c:forEach>
</table>
<hr>
<%--遍历Object数组
for(Object :arr)
items表示遍历的数据源（遍历的集合）
var表示当前遍历到的数据
--%>
<%
    request.setAttribute("arr",new String[]{"1323232","21312312","213213"});
%>
<c:forEach items="${requestScope.arr}" var="i">
${i}
</c:forEach>
<%
    Map map=new HashMap();
    map.put("key1","value1");
    map.put("key2","value2");
    map.put("key3","value3");
    request.setAttribute("map",map);
%>
<c:forEach items="${requestScope.map}" var="entry">
    ${entry.key}
    ${entry.value}
</c:forEach><br/>
<%--遍历List集合---list中存放Student类，有属性：编号，用户名，密码，年龄，电话信息 --%>
<%
    List list=new ArrayList();
    for (int i = 1; i <=10 ; i++) {
        list.add(new Student(i,"username"+i,"pssword"+i,18+i,"phone"+i));
    }
    request.setAttribute("stus",list);
%>
<c:forEach items="${requestScope.stus}" var="stu">
    ${stu}
</c:forEach>

</body>
</html>