JAVA简单链接Oracle数据库,实现注册和登陆的功能

//User 用户的基本信息，也是USERINFO表中的3个列
package 登陆判断;

public class User {

		private String name;
		private String loginname;
		private String loginpsw;
		public String getName() {
			return name;
		}
		public void setName(String name) {
			this.name = name;
		}
		public String getLoginname() {
			return loginname;
		}
		public void setLoginname(String loginname) {
			this.loginname = loginname;
		}
		public String getLoginpsw() {
			return loginpsw;
		}
		public void setLoginpsw(String loginpsw) {
			this.loginpsw = loginpsw;
		}
}
//用于注册和登陆的小小代码块
package 登陆判断;

import java.util.Scanner;

public class In {

		public static User getUser(){
			User u = new User();
			Scanner sc = new Scanner(System.in);
			System.out.println("请输入登陆名");
			u.setLoginname(sc.nextLine());
			System.out.println("请输入密码");
			u.setLoginpsw(sc.nextLine());
			return  u;
		}
		public static User registerUser(){
			User u = new User();
			Scanner sc = new Scanner(System.in);
			System.out.println("请注册用户名名");
			u.setName(sc.nextLine());
			System.out.println("请注册登陆名");
			u.setLoginname(sc.nextLine());
			System.out.println("请注册密码");
			u.setLoginpsw(sc.nextLine());
			return  u;
		}
}


//登陆时的检查，判断登陆名和密码是否正确，正确则返回 用户名
package 登陆判断;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class Check {

		public static void checkUser(User u)
		{
			try {
				Class.forName("oracle.jdbc.driver.OracleDriver");
			} catch (ClassNotFoundException e) {
				e.printStackTrace();
			}
			String url = "jdbc:oracle:thin:@localhost:1521:orcl";
			String user = "scott";
			String password = "tiger";
			Connection conn = null;
			ResultSet rs = null;
			PreparedStatement pst = null;
			
			String sql = "Select name from USERINFO where loginname = ? and loginpsw = ? ";
			try {
				conn = DriverManager.getConnection(url, user, password);
				pst = conn.prepareStatement(sql);
				pst.setString(1, u.getLoginname());
				pst.setString(2,u.getLoginpsw());
				rs = pst.executeQuery(); 
				while(rs.next()){
					u.setName(rs.getString(1));
				}				
			} catch (SQLException e) {
				e.printStackTrace();
			}finally{
				try {
					rs.close();
					pst.close();
					conn.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
			if(u.getName() == null || u.getName().isEmpty()){
				System.out.println("登陆失败");
			}else{
				System.out.println("欢迎"+u.getName()+"登陆");
			}
			
		}
}


//注册界面，要判断 登陆名是否有重复，有重复则注册失败。有点小疑问，已用注释标出来
package 登陆判断;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class Register {

		public static void registUser(User u){
			
			try {
				Class.forName("oracle.jdbc.driver.OracleDriver");
			} catch (ClassNotFoundException e) {
				e.printStackTrace();
			}
			String url = "jdbc:oracle:thin:@localhost:1521:orcl";
			String user = "scott";
			String password = "tiger";
			Connection conn = null;
			String sql = "Insert Into USERINFO values(?,?,?)";
			PreparedStatement pst = null;
			
			//判断登陆名是否已经存在
			Statement s = null;
			ResultSet rs = null;
			String sql_ck = "Select LOGINNAME FROM USERINFO";
			try {
				conn = DriverManager.getConnection(url, user, password);
				pst = conn.prepareStatement(sql);
				pst.setString(1, u.getName());
				pst.setString(2, u.getLoginname());
				pst.setString(3, u.getLoginpsw());
				//判断登陆名是否已经存在
				s = conn.createStatement();
				rs = s.executeQuery(sql_ck);
				while(rs.next()){//为什么用 rs.getString(2)会提示 无效的索引呢
					if( rs.getString("LOGINNAME").equals(u.getLoginname()) ){
						System.out.println("登陆名已经存在，注册失败");
						break;
					}else{
						pst.executeUpdate();
						System.out.println("注册成功");
						break;
					}
				}	
			} catch (SQLException e) {
				e.printStackTrace();
			}finally{
				try {
					rs.close();
					pst.close();
					s.close();
					conn.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
			
			
		}
}


//main界面//
//数据库中表的结构式这样
//name(用户名，用于显示),
//loginname(登录名,即登陆时输入的ID)
//loginpsw(登陆时输入的密码)
package 登陆判断;

import java.util.Scanner;

public class Test {

	public static void main(String[] args) {

		int chos = 0;
		Scanner sc = new Scanner(System.in);
		System.out.println("\t\t登陆请按1\t\t注册请按2");
		chos = sc.nextInt();
		switch(chos){
		case 1: Check.checkUser(In.getUser());break;
		case 2: Register.registUser(In.registerUser());break;
		default: System.out.println("请输入正确的选择");break;
		}
	}

}