Java-JDBC操作

一、不使用注入方法

public void login(String username, String password) throws ClassNotFoundException, SQLException {
        // 1.註冊驅動
        Class.forName("com.mysql.jdbc.Driver");
        // 2.獲取連接
        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/數據庫名", "root", "root");
        // 3.創建執行sql語句的對象
        Statement stmt = conn.createStatement();
        // 4.書寫一個sql語句
        String sql = "select * from tbl_user where " + "uname='" + username + "' and upassword='" + password + "'";
        // 5.執行sql語句
        ResultSet rs = stmt.executeQuery(sql);
        // 6.對結果集進行處理
        if (rs.next()) {
            System.out.println("恭喜您，" + username + ",登錄成功!");
            System.out.println(sql);
        } else {
            System.out.println("賬號或密碼錯誤!");
        }
        //7.關閉
        if (rs != null)
            rs.close();
        if (stmt != null)
            stmt.close();
        if (conn != null)
            conn.close();
    }

二、使用注入方法

public void login1(String username, String password) throws ClassNotFoundException, SQLException {
        // 1.註冊驅動
        Class.forName("com.mysql.jdbc.Driver");
        // 2.獲取連接
        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/數據庫名", "root", "root");
        // 3.編寫sql語句
        String sql = "select * from tbl_user where uname=? and upassword=?";
        // 4.創建預處理對象
        PreparedStatement pstmt = conn.prepareStatement(sql);
        // 5.設置參數(給佔位符)
        pstmt.setString(1, username);
        pstmt.setString(2, password);
        // 6.執行查詢操作
        ResultSet rs = pstmt.executeQuery();
        // 7.對結果集進行處理
        if (rs.next()) {
            System.out.println("恭喜您，" + username + ",登錄成功!");
            System.out.println(sql);
        } else {
            System.out.println("賬號或密碼錯誤!");
        }
        //8.關閉
        if (rs != null)
            rs.close();
        if (pstmt != null)
            pstmt.close();
        if (conn != null)
            conn.close();
    }