如何通过java程序访问另一个系统的mysql数据库? [英] How to access the another system mysql database through java program?

问题描述

如何通过java程序访问另一个系统的mysql数据库?我正在使用下面的程序，但出现通信错误?连接另一个系统的mysql数据库需要做哪些更改?

How to access the another system mysql database through java program?Am using the following program but i have get the communication error?what are the changes are need to connect the another system mysql database?

  Public void dbconnection() {

            String name = "";
            String port = "3306";
            String user = "system";
            String pass = "system";
            String dbname = "cascade_demo";
            String host="192.168.1.61";

            try {

                Class.forName("com.mysql.jdbc.Driver");

                  String url = "jdbc:mysql://"+host+":"+  port + "/" + dbname;
                System.out.println("URL:" + url);
                Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                Connection con = DriverManager.getConnection(url, user, pass);
                String qry2 = "select * from item_master";
                Statement st = con.createStatement();
                ResultSet rs = st.executeQuery(qry2);
                while (rs.next()) {

                    name = rs.getString(1);
                    System.out.println("Name:" + name);

                }


                rs.close();
                st.close();
                con.close();


            } catch (Exception e) {
                System.out.println("Exception:" + e);
            }
        }

推荐答案

您不是在创建驱动程序类的实例:

You're not creating an instance of the driver class:

Class.forName("com.mysql.jdbc.Driver").newInstance();

[更新:毕竟没有必要，忽略这一点]

[update: not necessary after all, ignore that]

而且您还引用了sun.jdbc.odbc.JdbcOdbcDriver"，这有必要吗?如果是这样，你不应该也实例化它吗?[更新:可能不是]

And you're also referencing "sun.jdbc.odbc.JdbcOdbcDriver", is that necessary? If so, shouldn't you instantiate it also? [update: probably not]

如果它适用于 localhost，而不是指定的 IP，则需要配置 mysql 以侦听所有端口.

If it works with localhost, and not with the IP specified, you need to configure mysql to listen on all ports.

jcomeau@intrepid:/tmp$ cat dbconnection.java; javac dbconnection.java; sudo java -cp .:/usr/share/maven-repo/mysql/mysql-connector-java/5.1.16/mysql-connector-java-5.1.16.jar  dbconnection
import java.sql.*;
public class dbconnection {
 public static void main(String args[]) {
  String name = "";
  String port = "3306";
  String user = "root";
  String pass = "";
  String dbname = "imagetagging";
  String host="127.0.0.1";
  try {
   Class.forName("com.mysql.jdbc.Driver").newInstance();
   String url = "jdbc:mysql://"+host+":"+  port + "/" + dbname;
   System.out.println("URL:" + url);
   //Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
   Connection con = DriverManager.getConnection(url, user, pass);
   String qry2 = "select * from taggers";
   Statement st = con.createStatement();
   ResultSet rs = st.executeQuery(qry2);
   while (rs.next()) {
    name = rs.getString(1);
    System.out.println("Name:" + name);
   }
   rs.close();
   st.close();
   con.close();
  } catch (Exception e) {
   System.out.println("Exception:" + e);
  }
 }
}
URL:jdbc:mysql://127.0.0.1:3306/imagetagging
Name:1
Name:2
Name:3
Name:4
Name:5
Name:6
Name:7
Name:8
Name:9
Name:10
Name:11
Name:12
Name:13
Name:14
Name:15
Name:16
Name:17
Name:18
Name:19
Name:20
Name:21

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