connection对象

Connection功能

1. 获取执行SQL的对象

   • 普通执行SQL对象：Statement createStatement()
   • 预编译SQL的执行SQL对象，防止SQL注入：PreparedStatement prepareStatement(sql)
   • 执行存储过程的对象：CallableStatement prepareCall(sql)

2. 事务管理

   • 开启事务：setAutoCommit(boolean autoCommit)，true为自动提交，false为手动提交
   • 提交事务：commit()
   • 回滚事务：rollback()

   package com.sympa.lesson01;
   
   import javax.swing.plaf.nimbus.State;
   import java.sql.*;
   
   //我的第一个JDBC程序
   public class JdbcFirstDemo {
       public static void main(String[] args) throws ClassNotFoundException, SQLException {
           //1.加载驱动
           //Class.forName("com.mysql.cj.jdbc.Driver"); //固定写法，加载驱动
           //2.用户信息和url
           String url = "jdbc:mysql://127.0.0.1:3306/jdbcstudy?serverTimezone=UTC&userUnicode=true&characterEncoding=utf8&useSSL=false";
           String username = "root";
           String password = "";
           //3.连接成功，数据库对象 Connection 代表数据库
           Connection connection = DriverManager.getConnection(url, username, password);
           //4.执行SQL的对象
           Statement statement = connection.createStatement();
   
           String sql = "select * from users";
           String sql1 = "update users set password = 114514 where id = 1";
   
           ResultSet resultSet = null; //返回的结果集
           try {
               //开启事务
               connection.setAutoCommit(false);
               int resultSet1 = statement.executeUpdate(sql1);
               resultSet = statement.executeQuery(sql);
               while(resultSet.next()){
                   System.out.println("id=" + resultSet.getObject("id"));
                   System.out.println("name=" + resultSet.getObject("name"));
                   System.out.println("password=" + resultSet.getObject("password"));
                   System.out.println("email=" + resultSet.getObject("email"));
                   System.out.println("birthday=" + resultSet.getObject("birthday"));
               }
               //提交事务
               connection.commit();
           } catch (Exception e) {
               //回滚事务
               connection.rollback();
               e.printStackTrace();
           }
           //5.释放连接
           resultSet.close();
           statement.close();
           connection.close();
       }
   }