Question

con = DriverManager.getConnection出错

代码就是这样：package mysql;import java.sql.*;public class Mysql { public static void main(String[] args) { Connection con = null; Statement sql; ResultSet rs; try { Class.forName("com.mysql.cj.jdbc.Driver"); System.out.println("成功"); } catch(Exception e) {} String uri = "jdbc:mysql://localhost:3306/students"; String user = "root"; String password = ""; try { con = DriverManager.getConnection(uri, user, password); } catch(SQLException e) { System.out.println("失败"); } try { sql = con.createStatement(); rs = sql.executeQuery("SELECT * FROM message"); while(rs.next()) { String number = rs.getString(1); String name = rs.getString(2); Date date = rs.getDate(3); float height = rs.getFloat(4); System.out.printf("%s\t",number); System.out.printf("%s\t",name); System.out.printf("%s\t",date); System.out.printf("%.2f\n",height); } con.close(); } catch(SQLException e) { System.out.println(e); } }}运行后一直显示

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Answer 1

getConnection("jdbc:odbc:moon","","") 这是一个url的典型写法: 分别表示服务器地址，端口，数据库名 当然也可以把用户名和密码写在一起。 createStatement = 创建用于执行静态 SQL 语句并返回它所生成结果的对象。之后，就可以使用executeQuer()这个方法来执行SQL词句