javaBean分析

package com.ldf.domain;
/**
 * 实体bean
 */
import java.io.serializable;
import java.util.date;

public class user implements serializable{
	
	private int id;
	private string username; 
	private string password;
	private string email;
	private date birthday;
	
	public user() {
		super();
	}
	
	public user(int id, string username, string password, string email,
			date birthday) {
		super();
		this.id = id;
		this.username = username;
		this.password = password;
		this.email = email;
		this.birthday = birthday;
	}
	@override
	public string tostring() {
		return "user [id=" + id + ", username=" + username + ", password="
				+ password + ", email=" + email + ", birthday=" + birthday
				+ "]";
	}
	public int getid() {
		return id;
	}
	public void setid(int id) {
		this.id = id;
	}
	public string getusername() {
		return username;
	}
	public void setusername(string username) {
		this.username = username;
	}
	public string getpassword() {
		return password;
	}
	public void setpassword(string password) {
		this.password = password;
	}
	public string getemail() {
		return email;
	}
	public void setemail(string email) {
		this.email = email;
	}
	public date getbirthday() {
		return birthday;
	}
	public void setbirthday(date birthday) {
		this.birthday = birthday;
	}
}

1.实现serializable接口是为了服务器重启或者内存溢出之后,能够实现session的钝化和激活两种状态,钝化表示session数据能够进行存盘操作,激活表示服务器从盘中读取session数据.

public class user implements serializable{

2.字段的定义统一小写且约定必须符合四者的统一,javabean中的字段定义,前端页面的标签name值,后台request.getparameter的形参,以及数据库中字段的定义要保持一致.

	private int id;
	private string username; 
	private string password;
	private string email;
	private date birthday;

3.在不写任何构造器的情况下,系统会默认给出无参构造器,但如果给出了有参构造器,那么必须显式的给出无参构造器.构造器的作用在于初始化参数.

	public user() {
		super();
	}
	
	public user(int id, string username, string password, string email,
			date birthday) {
		super();
		this.id = id;
		this.username = username;
		this.password = password;
		this.email = email;
		this.birthday = birthday;
	}

4.重写tostring方法,单纯调用对象时,系统会自动调用tostring方法,如果没有重写tostring方法,那么会调用object超级父类的tostring方法,执行结果是该对象的地址值.重写该tostring方法后,系统也会自动调用tostring方法,但是是调用重写后的tostring方法.输出的是自定义的信息.

	@override
	public string tostring() {
		return "user [id=" + id + ", username=" + username + ", password="
				+ password + ", email=" + email + ", birthday=" + birthday
				+ "]";
	}

5.getter/setter方法的作用在于调用封装后的字段,在框架中是具有调用属性的作用.