JDBC 原始完整程序回顾

Dear 丶 2022-12-22 06:12 132阅读 0赞

public static void main(String[] args) { 
            Connection connection = null;
            PreparedStatement preparedStatement = null;
            ResultSet resultSet = null;
            try { 
                //加载数据库驱动
    
                Class.forName("com.mysql.jdbc.Driver");
                //通过驱动管理类获取数据库链接
                connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8", "root", "root");
                //定义sql语句 ?表示占位符
                String sql = "select * from user where username = ?";
                //获取预处理
                statement preparedStatement = connection.prepareStatement(sql);
                //设置参数，第一个参数为sql语句中参数的序号（从1开始），第二个参数为设置的参数值
                preparedStatement.setString(1, "王五");
                //向数据库发出sql执行查询，查询出结果集
                resultSet = preparedStatement.executeQuery();
                //遍历查询结果集
                while (resultSet.next()) { 
                    System.out.println(resultSet.getString("id") + " " + resultSet.getString("username"));
                }
            } catch (Exception e) { 
                e.printStackTrace();
            } finally { 
                //释放资源
                if (resultSet != null) { 
                    try { 
                        resultSet.close();
                    } catch (SQLException e) { 
                        e.printStackTrace();
                    }
                }
                if (preparedStatement != null) { 
                    try { 
                        preparedStatement.close();
                    } catch (SQLException e) { 
                        e.printStackTrace();
                    }
                }
                if (connection != null) { 
                    try { 
                        connection.close();
                    } catch (SQLException e) { 
                        e.printStackTrace();
                    }
                }
            }
        }