JDBC 信息管理系统小实例

package com;

import java.util.Scanner;

public class SimpleSystem
{
SqlHelper helper = new SqlHelper();
Scanner scanner = new Scanner(System.in);

public static void main(String[] args)
{
new SimpleSystem().go();
}

public void go()
{
try{
helper.sqlSetup();
int rowNum = verify();
doThing(rowNum);
exit();
}catch(Exception ex){ex.getMessage();}
}

public int verify() throws Exception
{
System.out.println("Welcome to this system");
int rowNum = 0;
while(rowNum == 0)
{
System.out.println("Please type in username");
String username = scanner.nextLine();
System.out.println("Please type in password");
String password = scanner.nextLine();
rowNum = helper.login(username, password);

}
return rowNum;
}

public void doThing(int rowNum) throws Exception
{
if(rowNum == 1)
{
SuperUser sUser = new SuperUser();
sUser.introduction();

while(true)
{
System.out.println("Press 'N' to exit or type in your option: ");
String option = scanner.nextLine().toUpperCase();
switch(option)
{
case "A":
sUser.add(helper);
break;
case "D":
sUser.delete(helper);
break;
case "E":
sUser.edit(helper);
break;
case "S":
sUser.select(helper);
break;
case"N":
return;
default:
System.out.println("Correct your option!");
break;
}
}
}else
{
CommonUser cUser = new CommonUser();
cUser.introduction();

while(true)
{
System.out.println("Press 'N' to exit or type in your option: ");
String option = scanner.nextLine().toUpperCase();
switch(option)
{

case "S":
cUser.select(helper);
break;
case"N":
return;
default:
System.out.println("Correct your option!");
break;
}
}
}

}

public void exit()
{
scanner.close();
System.out.println("System exited!");
}
}

package com;

import java.sql.*;

public class SqlHelper
{
private Connection con;
private String driver = "com.mysql.jdbc.Driver";
private String url = "jdbc:mysql://127.0.0.1:3306/?autoReconnect=true&useSSL=false";
private String user = "root";
private String passwd = "lly";
private Statement stmt = null;

public void sqlSetup()
{
try
{
Class.forName(driver).newInstance();
con = DriverManager.getConnection(url,user,passwd);
System.out.println("Server is connected.");

stmt= con.createStatement();
stmt.executeQuery("USE prac");
System.out.println("Database accessed.");
}catch(Exception e)
{
System.out.println("MYSQL ERROR: " + e.getMessage());
}
}

public int login(String username, String password) throws SQLException
{
int rowNum = 0;
ResultSet rs = select(username);
if(rs.next())
{
if(password.equals(rs.getString(3)))
{
System.out.println("Successfully login!");
rowNum = rs.getInt(1);
}
else
System.out.println("Wrong password! Try again.");
}else
System.out.println("User do not exist!");
return rowNum;
}

public ResultSet select(String name) throws SQLException
{
return stmt.executeQuery("SELECT * FROM user WHERE name = '"+name+"'");
}

public int insert(String name, String pwd) throws SQLException
{
return	stmt.executeUpdate("INSERT INTO user(name, password) VALUES('"+name+"', '"+pwd+"')");
}

public int delete(String name) throws SQLException
{
return stmt.executeUpdate("DELETE FROM user WHERE name = '"+name+"'");
}

public int edit(String oldName, String newName, String pwd) throws SQLException
{
return stmt.executeUpdate("UPDATE user SET name = '"+newName+"', password = '"+pwd+"' WHERE name = '"+oldName+"'");
}

}

package com;

import java.util.Scanner;

public abstract class User
{
Scanner scanner = new Scanner(System.in);
public abstract void introduction();
}

package com;

import java.sql.ResultSet;
import java.sql.SQLException;

class SuperUser extends User
{
public void introduction()
{
System.out.println("You're the administrator of this System.");
System.out.println("Your rights are as follow:");
System.out.println("A -Add an user.");
System.out.println("D -Delete an user");
System.out.println("E -Edit an user infomation");
System.out.println("S -Search users");
System.out.println("N -Exit");
}

public void add(SqlHelper helper) throws SQLException
{
boolean run = true;
while(run)
{
System.out.println("Please type in new username: ");
String username = scanner.nextLine();
ResultSet sRs = helper.select(username);
if(!sRs.next())
{
while(true)
{
System.out.println("Please type in 8-digits password");
String password = scanner.nextLine();
if(password.length() == 8)
{
int iRs = helper.insert(username, password);
if(iRs == 1)
{
System.out.println("New user has been added!");
run = false;
break;
}
}else
System.out.println("Password is not 8 digit! Try again.");
}
}else
System.out.println("User exist! Try again.");
}

}

public void delete(SqlHelper helper)throws SQLException
{
System.out.println("Please type in username: ");

String username = scanner.nextLine();
if(!username.equals("admin"))
{
int flag = helper.delete(username);
if(flag == 1)
System.out.println("User has been deleted!");
else
System.out.println("User do not exist!");
}else
System.out.println("Administrator accout can not be deleted!");

}

public void edit(SqlHelper helper)throws SQLException
{
System.out.println("Please type in the username you want to edit: ");

String oldName = scanner.nextLine();
ResultSet rs = helper.select(oldName);
if(rs.next())
{
System.out.println("Type in new username: ");
String newName = scanner.nextLine();
while(true)
{
System.out.println("Type in new password: ");
String newPwd = scanner.nextLine();
if(newPwd.length() == 8)
{
int flag = helper.edit(oldName, newName, newPwd);
if(flag == 1){
System.out.println("User has been edit!");
break;
}
}else
System.out.println("Password is not 8 digit! Try again.");
}
}else
System.out.println("User do not exist! Try again.");

}

public void select(SqlHelper helper) throws SQLException
{
System.out.println("Please type in the username you want to search: ");

String username = scanner.nextLine();
ResultSet rs = helper.select(username);
if(rs.next())
{
System.out.println("User info is as follow: ");
System.out.println("User_id: "+rs.getInt(1)+" Username: "+rs.getString(2)+"Password: "+rs.getString(3));
}else
System.out.println("User do not exist!");

}
}

package com;

import java.sql.ResultSet;
import java.sql.SQLException;

class CommonUser extends User
{
public void introduction()
{
System.out.println("You're the common user of this System.");
System.out.println("Your rights are as follow:");
System.out.println("S -Search users");
System.out.println("N -Exit");
}

public void select(SqlHelper helper) throws SQLException
{
System.out.println("Please type in the username you want to search: ");
String username = scanner.nextLine();
ResultSet rs = helper.select(username);
if(rs.next())
{
System.out.println("User info is as follow: ");
System.out.println("User_id: "+rs.getInt(1)+" Username: "+rs.getString(2)+"Password: "+rs.getString(3));
}else
System.out.println("User do not exist!");
}
}