javaweb探索篇（三)jsp,el,jstl

<%@ page import="java.util.Map" %>
<%@ page import="java.util.HashMap" %><%--
  Created by IntelliJ IDEA.
  User: wangsheng
  Date: 2022/2/11
  Time: 17:24
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


<%--声明类--%>
<%!
    private  Integer id;
    private  String name;
    private Mapmap;
%>
<%--声明静态代码块--%>
<%!
   static {
      Map map=new HashMap<>() ;
        map.put("key1","value1");
       map.put("key2","value2");
   }
%>
<%--方法--%>
<%!
    public  static int abc(){
        return 10+20;
    }
%>
<%--内部类--%>
<%!
    public class A{
        private  Integer id;
        private  String name;
        private Mapmap;
    }
%>
<%--输出脚本--%>
<%=12%>

<%=map%>

<%=request.getParameter("username")%>


<%--代码块脚本--%>
<%
 int i=12;
 if(i==12){
     System.out.println("小哥哥很帅");
 }else{
     System.out.println("小哥哥不睡觉吗？");
 }
%>
<%
    String username=request.getParameter("username");
    System.out.println("请求参数是"+username);
%>


    <%for(int j=1;j<=5;j++){
    %>
    
<%
    }
%>

       
 第<%=j%>行
    

El表的式主要的作用是输出域中的对象
EL表达式的值是:${key}

<%--
  Created by IntelliJ IDEA.
  User: wangsheng
  Date: 2022/2/12
  Time: 17:52
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


<%
    pageContext.setAttribute("key1","pageCotext1");
    pageContext.setAttribute("key2","pageCotext2");
    request.setAttribute("key","request");
    session.setAttribute("key","session");
    application.setAttribute("key","aplliction");
%>
EL中的四大域对象
     pageScope=======>pageContext域

      值是:${pageScope.key1}

     requsetScope=======>Requset域

       值是:${requestScope.key}

     sessionScope=======>session域

         值是:${sessionScope.key}

     apllicationScope=======>ServletContext域

         值是:${applicationScope.key}

<%@ page import="java.util.HashMap" %>
<%@ page import="java.util.Map" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="C" uri="http://java.sun.com/jsp/jstl/core" %>
<%--
  Created by IntelliJ IDEA.
  User: wangsheng
  Date: 2022/2/12
  Time: 19:57
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


<%-- 
   作用：set标签可以在域对象中保存数据
        scope:域对象
        var:设置key
        value:设置值
   --%>
   保存之前:${requestScope.abc}

   
   保存之后:${requestScope.abc}

  <%-- 
      作用:判断
      test:EL判断表达式  式子成立时执行类容执行
  --%>
   
       12等于12
   

<%request.setAttribute("height",168);%>
<%--
    
    

  作用:多路判断 相当于swtich case
  when:表示满足条件 等同于case
  ohterwise:表达其他条件 等同于defalut
--%>

    
        很高
    
    
        还可以
    
    
        有点矮
    


<%--
    作用:遍历输出条件
    begin:设置开始索引
    end:设置结束的索
    var:设置变量
    items：遍历的数据源
--%>

    

    

        
第${i}行
    
    


<%--遍历数组--%>
<%pageContext.setAttribute("arr",new String[]{"12354444","125444444","5411474444"});%>

    ${ites}


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

    ${values.key}

student类 

package com.java.Person;

public class Student {
    private Integer id;
    private String name;
    private String password;
    private Integer age;
    private String phone;

    public Student() {
    }

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

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

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

jsp文件

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page import="com.java.Person.Student" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.List" %>
<%--
  Created by IntelliJ IDEA.
  User: wangsheng
  Date: 2022/2/12
  Time: 20:47
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


遍历list集合
<%
    List student=new ArrayList<>();
    for(int i=1;i<=5;i++){
        student.add(new Student(i,"name"+i,"password"+i,18+i,"123444852"+i));
    }
    request.setAttribute("student",student);
%>

     

    

        
id
        
name
        
password
        
age
        
phone
        
操作
    
 

         
${stu.id}
         
${stu.name}
         
${stu.password}
         
${stu.age}
         
${stu.phone}
         
删除
     
 

结果