远程访问数据库-嵌套异常

Question

我想在我的java程序中连接到远程数据库ssh，所以我为此编写了一个java代码，我可以从我的代码ssh到数据库服务器但我无法访问数据库，这个是我的输出，其中包含错误： （这个链接是我之前的问题link，和这个问题有关）

hi
identity added
session created.
session connected.....
shell channel connected....
connecting to database ...
db Method...
try-catch
Connecting to database...
DB_URL : jdbc:mysql://localhost:3366/DBNAME
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception:

** BEGIN NESTED EXCEPTION **

com.mysql.jdbc.CommunicationsException
MESSAGE: Communications link failure due to underlying exception:

** BEGIN NESTED EXCEPTION **

java.io.EOFException
MESSAGE: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.

STACKTRACE:

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:1997)
        at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:573)
        at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1044)
        at com.mysql.jdbc.Connection.createNewIO(Connection.java:2748)
        at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
        at java.sql.DriverManager.getConnection(DriverManager.java:664)
        at java.sql.DriverManager.getConnection(DriverManager.java:247)
        at Main.connectToDB(Main.java:78)
        at Main.main(Main.java:49)


** END NESTED EXCEPTION **



Last packet sent to the server was 0 ms ago.

STACKTRACE:

com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception:

** BEGIN NESTED EXCEPTION **

java.io.EOFException
MESSAGE: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.

STACKTRACE:

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:1997)
        at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:573)
        at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1044)
        at com.mysql.jdbc.Connection.createNewIO(Connection.java:2748)
        at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
        at java.sql.DriverManager.getConnection(DriverManager.java:664)
        at java.sql.DriverManager.getConnection(DriverManager.java:247)
        at Main.connectToDB(Main.java:78)
        at Main.main(Main.java:49)


** END NESTED EXCEPTION **



Last packet sent to the server was 0 ms ago.
        at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:641)
        at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1044)
        at com.mysql.jdbc.Connection.createNewIO(Connection.java:2748)
        at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
        at java.sql.DriverManager.getConnection(DriverManager.java:664)
        at java.sql.DriverManager.getConnection(DriverManager.java:247)
        at Main.connectToDB(Main.java:78)
        at Main.main(Main.java:49)


** END NESTED EXCEPTION **



Last packet sent to the server was 1 ms ago.
        at com.mysql.jdbc.Connection.createNewIO(Connection.java:2820)
        at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
        at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
        at java.sql.DriverManager.getConnection(DriverManager.java:664)
        at java.sql.DriverManager.getConnection(DriverManager.java:247)
        at Main.connectToDB(Main.java:78)
        at Main.main(Main.java:49)
Goodbye!
done

我运行这段代码

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import com.jcraft.jsch.Channel;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;

public class Main {

    public static void main(String[] arg) {
        try {
                System.out.println("hi");
            JSch jsch = new JSch();

            String user = "***";
            String host = "**.**.***.***";
            int port = 22;
            String privateKey = "id_rs";

            jsch.addIdentity(privateKey);
            System.out.println("identity added ");

            Session session = jsch.getSession(user, host, port);
            System.out.println("session created.");

            java.util.Properties config = new java.util.Properties();
            config.put("StrictHostKeyChecking", "no");
            session.setConfig(config);

            session.connect();
           session.setPortForwardingL( 3366, host, 3306)  ;

            System.out.println("session connected.....");

            Channel channel = session.openChannel("sftp");
            channel.setInputStream(System.in);
            channel.setOutputStream(System.out);
            channel.connect();
            System.out.println("shell channel connected....");
            System.err.println("connecting to database ...");

           connectToDB();

          System.out.println("done");

        } catch (Exception e) {
            System.err.println(e);
        }
    }


        static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
        static String databaseName ="DBNAME";
       static  int lport = 3366;
        static final String DB_URL = "jdbc:mysql://localhost:"+lport+"/"+databaseName;

        static final String USER = "***";
        static final String PASS = "***";

  public static void connectToDB() {
                System.out.println("db Method...");
                Connection conn = null;
                Statement stmt = null;
                try{
                        System.out.println("try-catch");
                        Class.forName("com.mysql.jdbc.Driver");

                        System.out.println("Connecting to database...");
                        System.err.println("DB_URL : "+DB_URL);
                        System.err.println(USER+":"+PASS+";");
                        conn = DriverManager.getConnection(DB_URL,USER,PASS);

                        System.out.println("hey!");
                        stmt = conn.createStatement();
                        String sql;
                        sql="SELECT * from Customer_Classes ; ";
                        ResultSet rs = stmt.executeQuery(sql);

                       try (BufferedWriter bw = new BufferedWriter(new FileWriter("a.txt"))) {
                                while(rs.next()){
                                      String name = rs.getString("ID");
                                      bw.write(name);
                                      bw.newLine();

                                      System.out.println(" name: " + name);
                                }
                                bw.close();
                        } catch (IOException e) {
                                e.printStackTrace();
                        }

                        rs.close();
                        stmt.close();
                        conn.close();
                }catch(SQLException se){
                        se.printStackTrace();
                }catch(Exception e){
                        e.printStackTrace();
                }finally{
                        try{
                                if(stmt!=null)
                                        stmt.close();
                        }catch(SQLException se2){
                            System.err.println("unable to close statement");
                        }
   }
                        try{
                                if(conn!=null)
                                        conn.close();
                        }catch(SQLException se){
                               System.err.println("unable to close connection");
                               se.printStackTrace();
                        }
                }
                System.out.println("Goodbye!");
        }
}

我在远程服务器中定义了一个具有所有权限的用户

GRANT ALL PRIVILEGES ON *.* TO 'USERNAME'@'IP' IDENTIFIED BY 'PASSWORD';

并将我的 Ip 添加到 my.cnf 中的绑定地址（在 DBserver 中）

这个错误意味着什么？我该如何解决？

Answer 1

1. 当通过端口转发连接时，数据库不会看到你原来的IP地址，而是本地的（localhost）。所以你的资助应该是GRANT ALL PRIVILEGES ON *.* TO 'USERNAME'@'localhost' IDENTIFIED BY 'PASSWORD';
2. Mysql 的bind-address 参数是用来配置server IP，而不是client IP。您应该将该设置（除非您需要它）保留为默认设置，因为无论如何您都将从 localhost 进行连接。
3. 如果Channel channel = session.openChannel("sftp");做了它看起来的事情（即将你连接到 SFTP 子系统），sshd 可能不会让你连接到其他地方。你应该使用Channel channel = session.openChannel("shell");
4. 检查服务器日志。