初识JDBC(Statement)

本文通过配置文件的方式链接数据库

package com.tan;
import com.mysql.jdbc.Driver;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
//JDBC程序示例
public class JDBC_test {
    public static void main(String[] args) throws SQLException, ClassNotFoundException, IOException {
        //1.加载配置文件
        InputStream inputStream = JDBC_test.class.getClassLoader().getResourceAsStream("jdbc.properties");
        Properties properties=new Properties();
        properties.load(inputStream);
        //2.读取配置文件
        String url = properties.getProperty("url");
        String username = properties.getProperty("username");
        String password = properties.getProperty("password");
        String driverClassName = properties.getProperty("driverClassName");
        //3.加载驱动
        Class.forName(driverClassName);
        //4.连接数据库，创建数据库对象
        Connection connection= DriverManager.getConnection(url,username,password);
        //5.执行SQL的对象
        Statement statement=connection.createSatement();
        //6.用执行SQL的对象来执行SQL
        String sql = "SELECT * FROM orders";
        ResultSet resultSet=statement.executeQuery(sql);//executeQuery是执行查询语句，还可以执行增删改查语句
        //返回的结果是一个链表
       while (resultSet.next()){
           System.out.println("order_num"+resultSet.getObject("order_num"));
           System.out.println("order_date"+resultSet.getObject("order_date"));
           System.out.println("cust_id"+resultSet.getObject("cust_id"));
       }
       //7.释放链接
        resultSet.close();
        statement.close();
        connection.close();
    }
}