无法连接到MySql

Question

我正在尝试连接到MySQL服务器，但出现无法处理的错误。

java.sql.SQLNonTransientConnectionException:无法创建到数据库服务器的连接。尝试重新连接3次。放弃。com.mysql.cj.jdbc.exceptions.SQLError.createSQLException（SQLError.java:110）com.mysql.cj.jdbc.exceptions.SQLError.createSQLException（SQLError.java:97）com.mysql.cj.jdbc.exceptions.createSQLException（SQLError.java:89）com.mysql.cj.jdbc.exceptions.SQLError.createSQLException（SQLError.java:63）在com.mysql.cj.cj.jdbc.exceptions.SQLError.createSQLException（SQLError.java:73）在com.mysql.cj.jdbc.ConnectionImpl.connectWithRetries（ConnectionImpl.java:902）在com.mysql.cj.jdbc.jdbc.ConnectionImpl.createNewIO（ConnectionImpl.java:827）在com.mysql.cj.jdbc.jdbc.ConnectionImpl.ConnectionImpl.456）在com.mysql.cj.jdbc.jdbc.ConnectionImpl.getInstancecom.mysql.cj.jdbc.NonRegisteringDriver.connect（NonRegisteringDriver.java:207）的java.sql.DriverManager.getConnection（DriverManager.java:664）的java.sql.DriverManager.getConnection（DriverManager.java:247）的Main.Main（Main.java:21）原因：com.mysql.cj.exceptions.cjexceptions:sun.reflect.nativeconstructoraccessormpl.newInstance0（本机方法）sun.reflect.nativeconstructoraccessormpl.newInstance（nativeconstructoraccessormpl.java:62）sun.reflect.DelegatingConstructorAccessorImpl.newInstance上的用户“chevica”@“people”对数据库“peoples”的访问被拒绝（DelegatingConstructorAccessorImpl.java:45）在com.mysql.cj.exceptions.ExceptionFactory.createException（ExceptionFactory.java:61）在com.mysql.cj.exceptions.ExceptionFactory.createException（ExceptionFactory.java:105）在com.mysql.cj.exceptions.exceptions.ExceptionFactory.createException中com.mysql.cj.protocol.a.NativeProtocol.checkErrorMessage（NativeProtocol.java:810）com.mysql.cj.protocol.a.NativeProtocol.checkErrorMessage（NativeProtocol.java:810）com.mysql.cj.protocol.a.NativeProtocol.checkErrorMessage（NativeProtocol.java:735）com.mysql.cj.cj.protocol.a.NativeProtocol（NativeProtocol.java:703）在com.mysql.cj.protocol.a.NativeProtocol.checkErrorMessage（NativeProtocol.java:132）在com.mysql.cj.protocol.a.NativeAuthenticationProvider.proceedHandshakeWithPluggableAuthentication（NativeAuthenticationProvider.java:557）在com.mysql.cj.protocol.a.NativeAuthenticationProvider.connect（NativeAuthenticationProvider.java:220）在com.mysql.cj.protocol.a.NativeProtocol.connect（NativeProtocol.java:1443）在com.mysql.cj.NativeSession.connect（NativeSession.java:165）在com.mysql.cj.jdbc.ConnectionImpl.connectWithRetries（ConnectionImpl.java:846）…在main.main的线程“main”中还有7个异常（Main.java:39）

代码：

import java.sql.*;

public class Main {

    // JDBC URL, username and password of MySQL server
    private static final String url = "jdbc:mysql://localhost:3306/Peoples?autoReconnect=true&useSSL=false";
    private static final String user = "chechevica";
    private static final String password = "**ur_SQLparol**";

    // JDBC variables for opening and managing connection
    private static Connection connection;
    private static Statement statement;
    private static ResultSet resultSet;

    public static void main(String[] args) {
        String query = "SELECT id_user FROM users";

        try {
            // opening database connection to MySQL server
            Class.forName("com.mysql.cj.jdbc.Driver");
            connection = DriverManager.getConnection(url, user, password);

            // getting Statement object to execute query
            statement = connection.createStatement();

            // executing SELECT query
            resultSet = statement.executeQuery(query);

            while (resultSet.next()) {
                int count = resultSet.getInt(1);
                System.out.println("Total number of users in the table : " + count);
            }
        } catch (SQLException sqlEx) {
            sqlEx.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } finally {
            //close connection ,stmt and resultSet here
            try { connection.close(); } catch(SQLException se) { /*can't do anything */ }
            try { statement.close(); } catch(SQLException se) { /*can't do anything */ }
            try { resultSet.close(); } catch(SQLException se) { /*can't do anything */ }
        }
    }
}

Answer 1

根本原因是用户chechevica无法访问人民DB：

Caused by: com.mysql.cj.exceptions.CJException: Access denied for user 'chechevica'@'%' to database 'peoples' at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at 

您只需要向该用户授予访问权限来解决您的问题，这样就可以了：

GRANT ALL PRIVILEGES ON peoples.* TO 'chechevica'@'%';

有关在MySQL中授予权限的更多详细信息，请阅读本文