【Javaweb】大中午的不来一首JDBC六部曲？（上）

<!--mysql的驱动-->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.17</version>
</dependency>

package com.hxl.test;
import java.sql.*;
public class TestJdbc {
    public static void main(String[] args) throws ClassNotFoundException, SQLException {
        //配置信息
        String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8";
        String username = "root";
        String password = "123456";
        //1.加载驱动
        Class.forName("com.mysql.jdbc.Driver");
        //2.连接数据库
        //DriverManager代表驱动管理
        //connection获得的这个代表数据库，数据库的所有操作，他都可以做
        Connection connection = DriverManager.getConnection(url, username, password);
        //3.向数据库发送SQL的对象Statement：CRUD
        //PreparedStatement这个是安全的，需要把SQL放进去，预编译
        Statement statement = connection.createStatement();
        //4.编写sql
        String sql = "select * from users;";
        //5.执行查询SQL，返回一个ResultSet :结果集
        //增删改都是用executeUpdate即可
        ResultSet rs = statement.executeQuery(sql);
        while(rs.next()){
            //这里如果知道类型就可以使用getInt/getString等类型，不知道的话直接可以用getObject
            System.out.println("id=" + rs.getObject("id"));
            System.out.println("name=" + rs.getObject("name"));
            System.out.println("password=" + rs.getObject("password"));
            System.out.println("email=" + rs.getObject("email"));
            System.out.println("birthday=" + rs.getObject("birthday"));
        }
        //6.关闭连接，释放资源（一定要做）先开的后关
        rs.close();
        statement.close();
        connection.close();
    }
}

package com.hxl.test;
import java.sql.*;
//使用预编译的，PreparedStatement
public class TestJdbc2 {
    public static void main(String[] args) throws Exception {
        //配置信息
        String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8";
        String username = "root";
        String password = "123456";
        //1.加载驱动
        Class.forName("com.mysql.jdbc.Driver");
        //2.连接数据库
        Connection connection = DriverManager.getConnection(url, username, password);
        //3.编写sql
        String sql = "insert into users(id, name, password, email, birthday) value(?,?,?,?,?)";
        //4.预编译
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        preparedStatement.setInt(1,2);//给第一个占位符？的值赋值为2
        preparedStatement.setString(2,"老二");//给第二个占位符？的值赋值为老二
        preparedStatement.setString(3,"123456");//给第三个占位符？的值赋值为123456
        preparedStatement.setString(4,"2@qqcom");//给第四个占位符？的值赋值为2@qqcom
        //外面的date是sql.date里面的是util
        preparedStatement.setDate(5,new Date(new java.util.Date().getTime()));//给第五个占位符？的值赋值为
        //5.执行sql
        int i = preparedStatement.executeUpdate();
        if(i>0){
            System.out.println("插入成功");
        }
        //6.关闭连接，释放资源（一定要做）先开的后关
        preparedStatement.close();
        connection.close();
    }
}