Question

我在网上找到的解决方案都没有。我一直在打

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException：通讯链接失败

我正在尝试从另一台服务器连接MySQL数据库。我可以向您保证，当我尝试使用PgAdmin软件连接数据库时，网址，用户和密码信息是正确的。但是，当我尝试使用Java代码执行时（通过NetBean 8.1），它失败了。好的，以下是我的代码：

import oracle.jdbc.pool.OracleDataSource;
import java.sql.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class Client9{
      public static void main(String[] args) {
           System.out.println("MySQL Connect Example.");
           Connection conn = null;
           String url = "jdbc:mysql://MySQLUrl:3306/";
           String dbName = "MySQL_dbName";
           String driver = "com.mysql.jdbc.Driver";
           String userName = "user"; 
           String password = "password";
           try {
                Class.forName(driver).newInstance();
                conn = DriverManager.getConnection(url+dbName,userName,password);
                System.out.println("Connected to the database");
                conn.close();
                System.out.println("Disconnected from database");
           } catch (Exception e) {
                e.printStackTrace();
           }
      }

}

错误信息如下所示：

run:
MySQL Connect Example.
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(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1117)
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:673)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1084)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2465)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2498)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2283)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:822)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:404)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:317)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at netiqcustomprov.Client9.main(Client9.java:35)
Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:3052)
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:597)
... 16 more
BUILD SUCCESSFUL (total time: 1 minute 0 seconds)

到目前为止我尝试过的解决方案：我已将ojdb14.jar和mysql-connector-java-5.1.23-bin.jar导入到库中。我尝试了所有3种不同的方法getConnection()

getConnection(String url)
（我的字符串url =＆＃34; jdbc：mysql：// MySQLUrl：3306 / MySQL_dbName？user = user＆amp; password = password＆＃34;）
getConnection(String url, Properties info)
getConnection(String url, String user, String password)

我还尝试使用以下命令注册驱动程序：

Driver myDriver = new oracle.jdbc.driver.OracleDriver();
DriverManager.registerDriver( myDriver );

我找到的解决方案之一是评论＆＃34; skip-networking＆＃34; my.cnf文件中的规则。但是，我在服务器中找不到这样的文件。（服务器基于Linux OS运行）

非常感谢协助解决这个问题。提前致谢

更新：查看我的回答。我再一次为我的愚蠢错误道歉。

Answer 1

最后我知道错误是什么。这真是一个愚蠢的错误。这是一个postgres db而不是mysql。所以，我只是更改了网址和驱动程序。

String url = "jdbc:postgresql:://MySQLUrl:3306/";
String driver = "org.postgresql.Driver";

对不起我的错误，感谢那些试图帮助我的人。

点击＆＃34;通讯链接失败＆＃34;我尝试使用JDBC连接到MySQL时出错

1 个答案: