九、JavaBean

实体类
JavaBean有特定的写法：
①必须要有一个无参构造
②属性必须私有化
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；
ORM：对象关系映射
①表——>类
②字段——>属性
③行记录——>对象
Person.java：

package com.ping.pojo;
//实体类一般都是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+'\''+
              '}';
  }
}

创建对应的数据库中的表。

<%
  //People people = new People();
  //people.setAddress();
  //people.setId();
  //people.setAge();
  //people.setName();
%>
<jsp:useBean id="people" class="com.ping.pojo.People" scope="page" />
<jsp:setProperty name="people" property="address" value="南京"/>
<jsp:setProperty name="people" property="id" value="1"/>
<jsp:setProperty name="people" property="age" value="20"/>
<jsp:setProperty name="people" property="name" value="ping"/>
<%-- <%=people.getAddress()%> --%>
姓名：<jsp:getProperty name="people" property="name"/>
年龄：<jsp:getProperty name="people" property="age"/>
序号：<jsp:getProperty name="people" property="id"/>
地址：<jsp:getProperty name="people" property="address"/>