第15周作业

题目1：

编写一个应用程序，输入用户名和密码，访问test数据库中t_login表（字段包括id、username、password），验证登录是否成功。

代码：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Scanner;


public class test {
    public static void main(String[] args) {
        Scanner s=new Scanner(System.in);
        String username= s.next();
        String password= s.next();
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con =DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","0000");
            Statement st=con.createStatement();
            ResultSet rs = st.executeQuery("select * from t_login where username = '"+username+"' and password = '"+password+"'");
            if(rs.next()){
                System.out.print("登录成功\n");
            }else{
                System.out.print("登录失败\n");
            }
            if(rs!=null){
                rs.close();
            }
            st.close();
            con.close();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }

    }

}

结果

题目2：

在上一题基础上，当登录成功后，将t_user表（id、name、sex、birthday）的信息进行显示（要求使用DB.java完成登录和获取t_user表中数据的操作），最后再对t_user表进行一条记录的添加操作。

代码：

import java.sql.*;
import java.util.Scanner;
public class Test {
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        DB db=DB.getInstance();
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入用户名 密码：");
        String username=sc.next();
        String password=sc.next();
        ResultSet rs =null;
        rs = db.excuteSelect("select * from t_login where username = ? and password = ?", new Object[]{username,password});
        try {
            if(rs.next()){
                System.out.println("登录成功");
                System.out.println("查询结果为：");
                rs = db.excuteSelect("select * from t_user", new Object[]{});
                char sex = ' ';
                while(rs.next()){
                    if(rs.getInt(3)==0){
                        sex = '男';
                    }else if(rs.getInt(3)==1){
                        sex = '女';
                    }
                    System.out.println("id: "+rs.getInt(1)+"   name: "+rs.getString(2)+"   sex: "+sex+"   birthday: "+rs.getString(4));                 
                }
                System.out.println("请输入 姓名 性别 生日");
                String name;
                String birthday;
                name=sc.next();
                sex=sc.next().charAt(0);
                birthday=sc.next();
                int isex = 0;
                if(sex=='男'){
                    isex=0;
                }else if(sex=='女'){
                    isex=1;
                }
                if(db.executeModify("insert into t_user (name,sex,birthday)values(?,?,?)", new Object[]{name,isex,birthday})>0){
                    System.out.println("添加成功");
                }
            }else{
                System.out.println("登录失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        db.close();
        sc.close();
    }
}

import java.sql.*;
public class DB {
    private Connection con;
    private PreparedStatement pre;
    private ResultSet rs;
    private static DB db;
    static{
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    private DB(){
        try {
            con=DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","0000");
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public static DB getInstance(){
        if(db==null){
            db=new DB();
        }
        return db;
    }
    public ResultSet excuteSelect (String sql ,Object[] args){
        try {
            pre=con.prepareStatement(sql);
            if(args.length!=0){
                for (int i = 0; i < args.length; i++) {
                    pre.setObject(i+1, args[i]);
                }
            }
            rs=pre.executeQuery();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return rs;
    }
    public int executeModify(String sql,Object[] args){
        int n=0;
        try {
            pre=con.prepareStatement(sql);
            if(args.length!=0){
                for (int i = 0; i < args.length; i++) {
                    pre.setObject(i+1, args[i]);
                }
            }
            n=pre.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return n;    
    }
    public void close(){
        try {
            if(rs!=null){
                rs.close();
            }
            pre.close();
            con. close();
        } catch (SQLException e) {
            e.printStackTrace();    
        }
    }
}

运行结果