复制public class jdbcConnection {      private staticConnectionconnection = null;      private static PreparedStatement preparedStatement = null;      private static ResultSet resultSet = null;      publicstatic void main(String[] args) {          try {              // 加载数据库驱动              Class.forName("com.mysql.jdbc.Driver");              // 通过驱动管理类获取数据库连接              connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/huodd",长文 "root", "1234");              // 定义sql语句 ? 表示占位符              String sql = "select id,username from user where id = ?";              // 获取预处理对象 statement              PreparedStatement preparedStatement = (PreparedStatement) connection.prepareStatement(sql);              // 设置参数 第一个参数为 sql 语句中参数的序号(从1开始) 第二个参数为 设置的源码库参数值              preparedStatement.setInt(1, 1);              // 向数据库发出sql执行查询 查询出结果集              resultSet = preparedStatement.executeQuery();              // 遍历查询结果集              while (resultSet.next()) {                  int id = resultSet.getInt("id");                  String username = resultSet.getString("username");                  // 封装对象                  Useruser = new User();                  user.setId(id);                  user.setUsername(username);                  System.out.println(user);              }          } catch (Exception ex) {              ex.printStackTrace();          } finally {              try {                  // 释放资源                  if (resultSet != null) {                      resultSet.close();                  }                  if (preparedStatement != null) {                      preparedStatement.close();                  }                  if (connection != null) {                      connection.close();                  }              } catch (Exception ex) {                  ex.printStackTrace();              }          }      }  }  1.2.3.4.5.6.7.8.9.10.11.12.13.14.15.16.17.18.19.20.21.22.23.24.25.26.27.28.29.30.31.32.33.34.35.36.37.38.39.40.41.42.43.44.45.46.47.48.49.亿华云