Java简化代码（封装）

代码（封装）"/>

Java简化代码（封装）

以前写的新闻发布系统代码重复且亢长，使用JavaBean封装后可以把java和jsp分离，使整个界面看上去更精简，也更方便。

  一.What？什么是 JavaBean？

1.JavaBean 是一种组件技术。

   javabean 技术有助于将JSP页面中的处理业务的逻辑代码与展示页面效果的显示代码分离

2.JavaBean 规则。

   1）有无参的构造函数

   2）成员属性私有化

   3）封装的属性如果需要被外所操作，必须编写public类型的setter、getter方法

3.JavaBean 分类。

   1）封装数据

   2）封装业务逻辑

二.Why? 为什么要用到 JavaBean? 

1. 使用 javabean 的好处就是：封装，重用 , 可读！

2.JavaBean 优点 。

   1）减少代码冗余，相同功能的代码不必重复编写。

   2）功能区分明确，相同功能写在一个类中。相似功能放在同一个包中

   3）提高代码的可维护性

三.部分封装代码展示 

 JavaBean封装java代码：

 其实就是把jsp页面的java代码封装到JavaResources的src里面；

 在JavaResources-src里建立三个包，分别是Dao包、entity包、util包

注：分别放数据库访问类、实体类、DBHelper类。

1. DBHelper类

package com.news.untils;
/*** 数据库帮助类* @author zjjt**/import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;public class DBHelper {// 加载驱动static {try {Class.forName("oracle.jdbc.driver.OracleDriver");} catch (Exception e) {e.printStackTrace();}}// 建立连接public static Connection getConn() {Connection conn = null;try {conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl", "scott", "123");} catch (Exception e) {e.printStackTrace();}return conn;}// 关闭连接public static void myClose(Connection conn, PreparedStatement ps, ResultSet rs) {try {if (conn != null && !conn.isClosed()) {conn.close();}if (ps != null) {ps.close();}if (rs != null) {rs.close();}} catch (Exception e) {e.printStackTrace();}}}

 2.用户实体类（entity）

package com.news.entity;/*** 用户实体类* * @author zjjt**/public class Users {private int userid;private String username;private String password;private String sex;private String hobby;private String address;private int urole;private String udate;public Users() {// TODO Auto-generated constructor stub}public Users(String username, String password) {super();this.username = username;this.password = password;}public Users(String username, String password, String sex, String hobby, String address, int urole, String udate) {super();this.username = username;this.password = password;this.sex = sex;this.hobby = hobby;this.address = address;this.urole = urole;this.udate = udate;}public Users(int userid, String username, String password, String sex, String hobby, String address, int urole,String udate) {super();this.userid = userid;this.username = username;this.password = password;this.sex = sex;this.hobby = hobby;this.address = address;this.urole = urole;this.udate = udate;}public int getUserid() {return userid;}public void setUserid(int userid) {this.userid = userid;}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 getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public String getHobby() {return hobby;}public void setHobby(String hobby) {this.hobby = hobby;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}public int getUrole() {return urole;}public void setUrole(int urole) {this.urole = urole;}public String getUdate() {return udate;}public void setUdate(String udate) {this.udate = udate;}@Overridepublic String toString() {return "Users [userid=" + userid + ", username=" + username + ", password=" + password + ", sex=" + sex+ ", hobby=" + hobby + ", address=" + address + ", urole=" + urole + ", udate=" + udate + "]";}}

 3.Dao 类

package com.news.dao;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import com.news.dao.IUsersDao;
import com.news.entity.Users;
import com.news.untils.DBHelper;/*** 用户模块的DAO接口* * @author Administrator**/
public class UsersDaoImpl implements IUsersDao {@Overridepublic Users adminUsersLogin(Users users) {// 1.定义所需的对象及变量Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;String sql = "select * from tb_news_users where username = ? and password = ?";Users u = null;// 2.赋值try {// 获取数据库连接conn = DBHelper.getConn();// 将定义的sql语句传入方法返回执行对象ps = conn.prepareStatement(sql);// 给占位符赋值ps.setString(1, users.getUsername());ps.setString(2, users.getPassword());// 返回结果集对象rs = ps.executeQuery();// 判断if (rs.next()) {u = new Users(rs.getInt("userid"), rs.getString("username"), rs.getString("password"),rs.getString("sex"), rs.getString("hobby"), rs.getString("address"), rs.getInt("urole"),rs.getString("udate"));}} catch (Exception e) {e.printStackTrace();} finally {DBHelper.myClose(conn, ps, rs);}// 返回return u;}public static void main(String[] args) {Users adminUsersLogin = new UsersDaoImpl().adminUsersLogin(new Users("admin", "123"));System.out.println(adminUsersLogin);}@Overridepublic int addUsersLogin(Users users) {// TODO Auto-generated method stubreturn 0;}@Overridepublic int setUsersPassword(Users users, String newPassword) {// TODO Auto-generated method stubreturn 0;}}

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