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。

Test.java

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

import javax.xml.transform.Result;


public class Test {
	public static void main(String[] args) throws SQLException, ClassNotFoundException {
	Connection con = null;
	Statement st = null;
	ResultSet rs = null;
	Scanner reader = new Scanner(System.in);
	System.out.println("输入用户名");
    String username=reader.next();
    System.out.println("输入密码");
    String password=reader.next(); 
	Class.forName("com.mysql.jdbc.Driver");       //加载驱动程序
	con=DriverManager.getConnection( "jdbc:mysql://localhost:3306/test","root","0000");   //创建数据库连接对象
	st=con.createStatement();
	rs = st.executeQuery("  select*from t_login where username= '"+username+"'  and password='"+password+"'");  //创建执行Sql语句
	if(rs.next()){
		System.out.println("登录成功");
	}
	else{
		System.out.println("登录失败");
	}
	if(rs!=null){
		rs.close();
	}
	st.close();
    con.close();
	}


}

运行结果

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。

1.DB.java

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

public class DB {
    private Connection con;
    private PreparedStatement pre;
    ResultSet rs;
    private static DB db;
    public static DB getInstance() {				//无参构造方法
        if(db ==null) {
            db = new DB();
        }
        return db;
        
    }

    DB(){
        try {
            con = DriverManager.getConnection(
            		"jdbc:mysql://localhost:3306/test","root","0000");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }   
    static {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    public ResultSet executeSelect(String sql,Object[] args) {   //查询数据方法
        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 executeUpdate(String sql,Object[] args) {		//修改数据
        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) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        
    }

}

2.Test.java

import java.sql.SQLException;
import java.util.Scanner;
public class Test {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("请输入用户名");
        String username = in.next();
        System.out.println("请输入用户名");
        String password = in.next();
        Object []a = {username, password};
        String sql = "select * from  t_login where username=? and password=?";
        DB db = DB.getInstance();   					//创建DB对象
        db.executeSelect(sql, a);
        try {
            if(db.rs.next()){
                System.out.println("登陆成功!");
                Object []b = new Object[0];
                sql = "select * from t_user ";
                db.executeSelect(sql, b);		
                while(db.rs.next()){					//显示t_user表内容;
                	String name = db.rs.getString(2);
                	String sex = db.rs.getString(3);
                	String birthday = db.rs.getString(4);
                    System.out.println("姓名:"+name+" 性别:"+sex+" 生日 :"+birthday+"");
                }
                System.out.println("请输入新记录:");
                String newname = in.next();
                String newsex = in.next();
                String newbirthday = in.next();
                Object []c = {newname, newsex , newbirthday};
                sql = "insert into t_user (name,sex,birthday) values(?,?,?)";
                int count = db.executeUpdate(sql, c); //添加记录;
                if(count == 0){
                    System.out.println("失败!");
                }else{
                    System.out.println("成功");
                }
            }else{
                System.out.println("失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

}

运行结果