解耦

降低依赖-编译期不依赖，运行期才依赖

1. 编译器依赖

package com.example.jdbc;

import java.sql.*;

public class JdbcDemo {

    public static void main(String[] args) throws SQLException {
        //1. 注册驱动
        DriverManager.registerDriver(new org.h2.Driver());
        //2. 获取链接
        Connection conn= DriverManager.getConnection("jdbc:h2:file:~/.h2/h2","root","123456");
        //3. 获取操作数据库的预处理对象
        PreparedStatement pstm=conn.prepareStatement("select * from account");
        //4. 执行SQL,得到结果集
        ResultSet rs = pstm.executeQuery();
        //5. 遍历结果集
        while(rs.next()){
            System.out.println(rs.getString("name"));
        }
        rs.close();
        pstm.close();
        conn.close();
    }

}

2. 运行期依赖

package com.example.jdbc;

import java.sql.*;

public class JdbcDemo {

    public static void main(String[] args) throws SQLException, ClassNotFoundException {
        //1. 注册驱动
        Class.forName("org.h2.Driver");
        //2. 获取链接
        Connection conn= DriverManager.getConnection("jdbc:h2:file:~/.h2/h2","root","123456");
        //3. 获取操作数据库的预处理对象
        PreparedStatement pstm=conn.prepareStatement("select * from account");
        //4. 执行SQL,得到结果集
        ResultSet rs = pstm.executeQuery();
        //5. 遍历结果集
        while(rs.next()){
            System.out.println(rs.getString("name"));
        }
        rs.close();
        pstm.close();
        conn.close();
    }

}