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在 ubuntu 服务器中连接 java 和 mysql

tag-icon • tag-icon networking server java mysql
在 ubuntu 服务器中连接 java 和 mysql

我正在尝试将 Java 应用程序与在与我的应用程序安装在同一台计算机上的 Virtual Box 上安装的 Ubuntu 服务器 14.04 上运行的 MySql 连接起来。我在 ubuntu 中安装了 mysql-server、mysql-client 和 libmysql-java，并且在 ubuntu 服务器内运行 sql 查询似乎运行正常。我的 java 应用程序是：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class UploadData {
 // The JDBC Connector Class.
  private static final String dbClassName = "com.mysql.jdbc.Driver";

  private static final String CONNECTION =
                          "jdbc:mysql://127.0.0.1/demodb";

  public static void main(String[] args) throws
                             ClassNotFoundException,SQLException
  {
    System.out.println(dbClassName);
    // Class.forName(xxx) loads the jdbc classes and
    // creates a drivermanager class factory
    Class.forName(dbClassName);

    // Properties for user and password. Here the user and password are both 'paulr'
    Properties p = new Properties();
    p.put("user","*******");
    p.put("password","******");

    // Now try to connect
    Connection c = DriverManager.getConnection(CONNECTION,p);

    System.out.println("It works !");
    c.close();
    }
}

我收到的错误是：

Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

 The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:389)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1038)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:338)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2237)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2270)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2069)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:794)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:389)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:399)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:325)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at server.UploadData.main(UploadData.java:32)

 Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:213)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:297)
... 15 more

任何建议都会很有帮助，

谢谢

答案1

当没有正在运行或正在监听的mysql服务时，会出现异常：

  • 启动 MySQL 服务器

  • 检查端口号，你在代码中使用了标准端口 3306

    private static final String dbClassName = "jdbc:mysql://127.0.0.1:<your_port_number>/demodb";

  • 使用虚拟机的 IP 地址

    private static final String dbClassName = "jdbc:mysql://<host_name_or_ip_address_of_the_database_server>:<your_port_number>/demodb";

  • 检查两台机器上的防火墙

  • Ping MySQL 服务器的主机以检查连接

  • 办理bind-address入住/etc/mysql/my.cnf

由于您在评论中提出了另一个问题

线程“main”中的异常 java.sql.SQLException：null，来自服务器的消息：“主机‘192.168.1.7’不允许连接到此 MySQL 服务器

这就是答案。

  • 检查 MySQL 表中的列mysql.user条目Host

    SELECT * FROM mysql.user;

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