JSTL基础部分

weifengfuxiufa / 2023-09-02 / 原文

在使用 JSTL时记得正确引入了 JSTL 标签库
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

jstl if标签判断

test 属性表示判断的条件（使用 EL 表达式输出）<br>
<c:if test="${12==12}">
    正确 <br>
</c:if>

jstl多路判断

<%--
<c:choose> <c:when> <c:otherwise>标签
作用：多路判断。跟 switch ... case .... default 非常接近
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 标签表示剩下的情况
<c:choose> <c:when> <c:otherwise>标签使用时需要注意的点：
1、标签里不能使用 html 注释，要使用 jsp 注释
2、when 标签的父标签一定要是 choose 标签
--%>

<% request.setAttribute("h",179);%>
<c:choose>
    <c:when test="${requestScope.h>180}">
        <h2>180+好高啊</h2>
    </c:when>
    <c:when test="${requestScope.h>170}">
        <h2>170+很棒</h2>
    </c:when>
    <c:otherwise>
        <h2>160+也行啦</h2>
    </c:otherwise>
</c:choose>

jstl foreach遍历Object数组**


<%-- 遍历 Object 数组
  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[]{"黑暗","黎明","破晓"});%>

<c:forEach items="${requestScope.arr}" var="item">
    ${item} <br>
</c:forEach>

遍历Map集合

<%
    Map<String, Object> map = new HashMap<>();
    map.put("key1","v1");
    map.put("key2","v2");
    map.put("key3","v3");
    request.setAttribute("map",map);
%>
<c:forEach items="${requestScope.map}" var="entry">
    ${entry}:<br> key: ${entry.key} value: ${entry.value}  <br>
<%--    ${entry}  <br>--%>
</c:forEach>

遍历List集合

Student类

点击查看代码

package com.hard.bean;

/**
 * 哈哈哈嗨
 * 功能:
 */
public class Student {
    private Integer id;
    private String name;
    private String password;
    private Integer age;
    private Integer phone;

    public Student() {
    }

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

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

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    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 Integer getPhone() {
        return phone;
    }

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

<%--遍历List集合--%>
<%
    List<Student> list = new ArrayList<>();
//    ctrl+p  查看类的属性
    list.add(new Student(1,"李白","123",18,1548));
    list.add(new Student(2,"杜甫","14513",19,11554548));
    list.add(new Student(3,"杜牧","14798",16,1348548));
    request.setAttribute("l",list);
%>
<c:forEach items="${requestScope.l}" var="stu">
<%--    通过调用getXxx方法访问对象属性--%>
    ${stu} <br>
    ${stu.id}
    ${stu.name}
    ${stu.password}
    ${stu.age}
    ${stu.phone} <br>
</c:forEach>