求用java实现简单的登录和注册功能，主要是为了了解怎样对数据库进行增删改查。和各种请求处理，

Question

如题所述

Answer 1

//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;
}
}

}