JSP学习（3）—— JSTL标签库

JSTL是为了替代JSP中的代码脚本。

一. 使用步骤

1.导入JSTL标签库的jar包

2.使用taglib指令引入标签库

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

二. core核心库使用

1. ：往域里保存数据

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


    <%
        request.setAttribute("key1", "value1");
    %>
    ${requestScope.key1} 


    

    
    
    
    ${requestScope.key2} 

2. ：做if判断（只能做if判断，不可以if-else）

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


    
    
        12等于12
    

3. ：可以做多路判断（与switch-case-default类似）

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


    <%
        request.setAttribute("height",178);
    %>

    
    
    
    
        
            很高
        
        
            高
        
        
            还行
        
        
            
                
                    凑和
                
                
                    矮
                
                
                    其他情况
                
            
        
    

4. ：遍历

①遍历普通数据 

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


    
    
    
        ${i}
    
    
    
            

        

                
第${i}行
            
        
    

②遍历Object数组

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    

 
    
    
    <%
        request.setAttribute("names",new String[]{"张三","李四","王二"});
    %>
    
        ${name}
    

③遍历Map

<%@ page import="java.util.Map" %>
<%@ page import="java.util.HashMap" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


    
    
    <%
        Map map = new HashMap<>();
        map.put("key1","value1");
        map.put("key2","value2");
        map.put("key3","value3");

        request.setAttribute("map",map);
    %>
    
        ${entry} 

        ${entry.key}  

        ${entry.value}  

        ${entry.key} = ${entry.value}

    

④遍历List

<%@ page import="java.util.List" %>
<%@ page import="pojo.Person" %>
<%@ page import="java.util.ArrayList" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


    
    
    <%
        List personList = new ArrayList<>();
        for(int i = 1; i <= 10; i++){
            personList.add(new Person("name"+i, "password"+i, 18+i));
        }
        request.setAttribute("person",personList);
    %>
    
        ${p} 

    

    
        

        

            
姓名
            
密码
            
年龄
        
    

            
${p.name}
            
${p.password}
            
${p.age}
        
    
    

package pojo;

public class Person {
    private String name;
    private String password;
    private Integer age;

    public Person() {
    }

    public Person(String name, String password, Integer age) {
        this.name = name;
        this.password = password;
        this.age = age;
    }

    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;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + ''' +
                ", password='" + password + ''' +
                ", age=" + age +
                '}';
    }
}

⑤forEach标签组合使用去遍历

<%@ page import="pojo.Person" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.List" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


    
    
    <%
        List personList = new ArrayList<>();
        for(int i = 1; i <= 10; i++){
            personList.add(new Person("name"+i, "password"+i, 18+i));
        }
        request.setAttribute("person",personList);
    %>

    
            

        

            
姓名
            
密码
            
年龄
        
        

                
${p.name}
                
${p.password}
                
${p.age}