入门JavaWeb之 JavaBean 实体类

news2024/11/27 0:47:47

JavaBean 有特定写法：

1.必须有一个无参构造

2.属性必须私有

3.必须有对应的 get/set 方法

一般用来和数据库的字段做映射

ORM：对象关系映射

表->类

字段->属性

行记录->对象

连接数据库

没有的话去 Settings -> Plugins 搜索 DataBase 下载

属性私有

按 alt + insert

Constructor 构造器：

Getter and Setter：

toString()：

MySQL 建表：

IDEA 显示表：

实体类和数据库中的表结构一一对应

代码如下：

package com.demo.entity;

//实体类和数据库中的表结构一一对应
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 + '\'' +
                '}';
    }
    
}

新建一个 javabean.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<body>

<%
    //People people = new People();
    //people.setId();
    //people.setName();
    //people.setAge();
    //people.setAddress();
%>

<jsp:useBean id="people" class="com.demo.entity.People" scope="page"/> <%-- page表示当前作用域 --%>

<jsp:setProperty name="people" property="id" value="1"/>
<jsp:setProperty name="people" property="name" value="hh"/>
<jsp:setProperty name="people" property="age" value="12"/>
<jsp:setProperty name="people" property="address" value="天河"/>

id：<jsp:getProperty name="people" property="id"/>
姓名：<jsp:getProperty name="people" property="name"/>
年龄：<jsp:getProperty name="people" property="age"/>
地址：<jsp:getProperty name="people" property="address"/>

</body>
</html>

执行，页面效果如下：