9.JavaBean
我們通常叫JavaBean爲：實體類。
JavaBean有其特定的寫法：
-
必須有一個無參構造。
-
屬性必須私有化
-
必須有對應的get/set方法。
一般用來和數據庫的字段作映射——>ORM;
ORM：對象關係映射。
-
表——>類
-
字段——>屬性
-
行記錄——>對象
舉例：
people表格：
create database Jsp;
use Jsp;
create table people(
`id` int(7) not null primary key,
`name` varchar(37) not null,
`age` int(3) not null,
`address` varchar(77) not null
)Engine = InnoDB default charset = utf8;
| id | name | age | address |
|---|---|---|---|
| 1 | Edwin | 17 | 海口 |
| 2 | Jarvis | 27 | 海口 |
| 3 | Rui | 7 | 海口 |
對應到Java中：
class Poeple{
private int id;
private String name;
private int age;
private String address;
}
class Add{
new People(1,"Edwin",17,"海口");
new People(2,"Jarvis",27,"海口");
new People(3,"Rui",7,"海口");
}
實際操作：
People類：
package com.edwin.pojo;
/**
* @author Edwin D
* @date 2020.6.9 下午 7:03
*/
//實體類我們一般都是和數據庫中的表一一對應的。
public class People {
private int id;
private String name;
private int age;
private String address;
public People() {
}
public People(int id, String name, int age, String address) {
this.id = id;
this.name = name;
this.age = age;
this.address = address;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "People{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
", address='" + address + '\'' +
'}';
}
}
JavaBean.jsp
<%@ page import="com.edwin.pojo.People" %><%--
Created by IntelliJ IDEA.
User: 元
Date: 2020.6.9
Time: 下午 7:27
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>JavaBean</title>
</head>
<body>
<%
// People people = new People();
// people.setId(1);
// people.setName("Edwin Duan");
// people.setAge(177);
// people.setAddress("海口");
%>
<%--ID：<%=people.getId()%>--%>
<%--姓名：<%=people.getName())%>--%>
<%--年齡：<%=people.getAge()%>--%>
<%--地址：<%=people.getAddress()%>--%>
<%--上下等價。--%>
<%--新建一個對象--%>
<jsp:useBean id="people" class="com.edwin.pojo.People" scope="page"/>
<%--賦值--%>
<jsp:setProperty name="people" property="id" value="1"/>
<jsp:setProperty name="people" property="name" value="Edwin 段"/>
<jsp:setProperty name="people" property="age" value="17"/>
<jsp:setProperty name="people" property="address" value="海口"/>
<%--取值--%>
ID：<jsp:getProperty name="people" property="id"/>
姓名：<jsp:getProperty name="people" property="name"/>
年齡：<jsp:getProperty name="people" property="age"/>
地址：<jsp:getProperty name="people" property="address"/>
</body>
</html>
輸出效果：
《成功的花》——冰心
成功的花，
人們只驚羨她現時的明豔！
然而當初她的芽兒，
浸透了奮鬥的淚泉，
灑遍了犧牲的血雨！
參考文獻
《【狂神說Java】JavaWeb入門到實戰》
2020.06.16