如何在Ubuntu中将MySQL与日食氧气连接

Question

我正在尝试使用以下Java代码使用Eclipse与mysql服务器创建JDBC连接

package dcv;

import java.sql.*;
public class testdb {

    public static void main(String[] args) {

          Connection con= null;
          try {
              Class.forName("com.mysql.jdbc.Driver");
                con = DriverManager.getConnection("jdbc:mysql://localhost:3306/sys", "root", "12345");
            } catch (Exception ex) {
            // TODO Auto-generated catch block
            System.out.println("Exception: "+ex);
    ex.printStackTrace();
        }
    }

}

但是，在运行类文件之后，在出现根名称，密码和架构没有错误的类文件之后，出现以下错误，并且我正在使用mysql-connector-java-5.1.30.jar文件。

Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database 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:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.Util.getInstance(Util.java:384)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:973)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:918)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2588)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2321)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:832)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
    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:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:417)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:344)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)
    at dcv.testdb.main(testdb.java:11)
Caused by: java.lang.NullPointerException
    at com.mysql.jdbc.ConnectionImpl.getServerCharacterEncoding(ConnectionImpl.java:3307)
    at com.mysql.jdbc.MysqlIO.sendConnectionAttributes(MysqlIO.java:1985)
    at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1911)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1288)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2506)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2539)
    ... 13 more

如何在Ubuntu OS中解决此问题？

Answer 1

尝试ping您的数据库服务器，看看是否能够连接。 否则解决网络问题，然后连接。

以下是用于创建数据库连接的代码

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


 DBConnection() throws SQLException, ClassNotFoundException {

            url = "jdbc:mysql://localhost/(your DB name)";

            user = "your user";

            password = "your password";

            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(url, user, password);
        }