jdbc链接数据库做简单案例

Posted 2020-10-30 你可别玩了

连接数据库方法

public class DButil {
    private DButil(){}
    static Connection conn;
    static{
        try{
            Class.forName("com.mysql.jdbc.Driver");
            String url="jdbc:mysql://localhost:3306/store";
            String username="root";
            String password="123456";
            conn=DriverManager.getConnection(url,username,password);
            }catch(Exception ex){
                throw new RuntimeException(ex+"数据库连接失败");
            }
    }
    public static Connection getConn(){
        return conn;
    }
    public static void close(Statement sta,Connection conn){
        if(sta!=null){
            try{
                sta.close();
            }catch(SQLException ex){}
        }
        if(conn!=null){
            try{
                conn.close();
            }catch(SQLException ex){}
        }
        
    }
    public static void close(ResultSet rs,Statement sta){
        if(rs!=null){
            try{
                rs.close();
            }catch(SQLException ex){}
        }
        if(sta!=null){
            try{
                sta.close();
            }catch(SQLException ex){}
        }
        
        
    }
}

通过此代码连接数据库，也就是DButil类

然后进行对数据库增删改查的操作，首先先写好sql语句，然后用PreparedStatement pst = conn.prepareStatement(sql);准备好执行sql语句，通过pst.set()方法  给sql里面的问号传值，最后用pst.executeUpdate()来完成增删改的操作，其返回的是int。

查询的话是pst.executeQuery()，返回的是ResultSe结果集;具体代码如下（商店管理系统）、

public class StoreApp {

    public static void main(String[] args) throws SQLException {
        ArrayList<Store> list = new ArrayList<Store>();
        while(true){
            Connection conn = DButil.getConn();
            switch(show()){
            case 1:
                selectMethod(list,conn);
                break;
            case 2:
                addMethod(conn);
                break;
            case 3:
                modifyMethod(conn);
                break;
            case 4:
                deleteMethod(conn);
                break;
            case 5:
                conn.close();
                return;
            }
        }

    }
    public static int show(){
        System.out.println("------------商城管理系统------------");
        System.out.println("1.查询商品信息");
        System.out.println("2.新增商品信息");
        System.out.println("3.修改商品信息");
        System.out.println("4.删除商品信息");
        System.out.println("5.退出");
        System.out.println("请输入您的选择");
        Scanner sc = new Scanner(System.in);
        return sc.nextInt();
    }
    public static void selectMethod(ArrayList<Store> list,Connection conn) throws SQLException{
        String sql = "select * from store";
        PreparedStatement pst = conn.prepareStatement(sql);
        ResultSet rs = pst.executeQuery();
        while(rs.next()){
            Store s= new Store();
            s.setSid(rs.getInt("sid"));
            s.setBrands(rs.getString("brands"));
            s.setSize(rs.getInt("size"));
            s.setPrice(rs.getDouble("price"));
            s.setCounts(rs.getInt("counts"));
            list.add(s);
            
        }
        for(int i =0;i<list.size();i++){
            System.out.println("商品编号为"+list.get(i).getSid()+"商品名称为"+list.get(i).getBrands()+"商品大小为"+list.get(i).getSize());
        }
        DButil.close(rs, pst);
        
    }
    public static void addMethod(Connection conn) throws SQLException{
        String sql = "INSERT INTO store(brands,size,price,counts) VALUE (?,?,?,?)";
        PreparedStatement pst = conn.prepareStatement(sql);
        Scanner sc =new Scanner(System.in);
        System.out.println("请输入商品名称");
        String brands = sc.next();
        System.out.println("请输入商品尺寸");
        int size = sc.nextInt();
        System.out.println("请输入商品价格");
        double price = sc.nextDouble();
        System.out.println("请输入商品数量");
        int counts = sc.nextInt();
        pst.setString(1,brands);
        pst.setInt(2, size);
        pst.setDouble(3, price);
        pst.setInt(4, counts);
        int a = pst.executeUpdate();
        if(a!=0){
            System.out.println("添加成功");
        }
        pst.close();
    }
    public static void     modifyMethod(Connection conn) throws SQLException{
        String sql = "UPDATE store SET PRICE = ? WHERE sid = ?";
        PreparedStatement pst = conn.prepareStatement(sql);
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入您要修改的产品的id");
        int sid = sc.nextInt();
        System.out.println("请输入修改后的价格");
        Double price = sc.nextDouble();
        pst.setDouble(1, price);
        pst.setInt(2, sid);
        int a = pst.executeUpdate();
        if(a!=0){
            System.out.println("修改成功");
        }
        pst.close();
    }
    public static void deleteMethod(Connection conn) throws SQLException{
        String sql = "delete from store where sid = ?";
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入您要删除产品的id");
        int sid = sc.nextInt();
        PreparedStatement pst = conn.prepareStatement(sql);
        pst.setInt(1, sid);
        int a = pst.executeUpdate();
        if(a!=0){
            System.out.println("删除成功");
        }
        pst.close();
    }
}