连接数据库主要分为六个步骤:
- 加载驱动
- 建立连接
- 准备SQL语句
- 执行SQL语句
- 处理结果
- 断开连接
我举一个查询的例子:
public static Connection lianJie() throws ClassNotFoundException, SQLException {
//1.加载驱动
Class.forName("com.mysql.cj.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/mysql?serverTimezone=GMT%2B8";
String user = "root";
String password = "123456";
//2.建立连接
Connection connections = DriverManager.getConnection(url, user, password);
//返回连接对象
return connections;
}
//调用它的方法如下:
public static void query(String query) throws SQLException, ClassNotFoundException {
//获取connection对象
Connection connection = DButil.lianJie();
//3.准备SQL语句
PreparedStatement pStatement = connection.prepareStatement(query);
//4.执行SQL语句
ResultSet resultSet = pStatement.executeQuery();
//检索此 ResultSet对象的列的数量,类型和属性。
ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
//返回此 ResultSet对象中的列数。
int column = resultSetMetaData.getColumnCount();
System.out.println("序号" + "\t" + "姓名" + "\t" + "年龄" + "\t" + "课程");
//5.处理结果遍历要查询的数据
while (resultSet.next()) {
//遍历行数
for (int i = 1; i <= column; i++) {
System.out.print(resultSet.getObject(i) + "\t");
}
System.out.println();
}
//6.关闭连接
resultSet.close();
pStatement.close();
connection.close();
}
}