It won't let me connect to the database from my plugin: "Cannot invoke "java.sql.Connection.prepareStatement(String)" because "connection" is null"

Question

I'm having problems connecting to the database from my plugin, previously I had done it and it left me normal, but from this other project it doesn't let me and I get errors, now this one is appearing and I don't understand

ConnectionMySQL.java

public class ConnectionMySQL {
    
    private Connection connection;

    public ConnectionMySQL(String host, int puerto, String database, String usuario, String password) {
        try {
            if (connection != null && !connection.isClosed()) {
                Bukkit.getConsoleSender().sendMessage(ChatColor.translateAlternateColorCodes('&', "&4Error al conectar a la base de datos."));
                return;
            }
            Class.forName("com.mysql.jdbc.Driver");
            this.connection = DriverManager.getConnection("jdbc:mysql://"+host+":"+puerto+"/"+database,usuario,password);
            Bukkit.getConsoleSender().sendMessage(ChatColor.translateAlternateColorCodes('&', "&aConectado a la base de datos correctamente."));
            
        } catch(SQLException | ClassNotFoundException e) {
            throw new RuntimeException("Hubo una excepción al conectar a la base de datos: ", e);   
        }
    }

    public Connection getConnection() {
        return connection;
    }
}

Main.java (onEnable)

private ConnectionMySQL connection;

public void onEnable() {
    
    FileConfiguration config = getConfig();

    // PATHS CONFIGS


    String host = "mysql.host";
    String port = "mysql.port";
    String database = "mysql.database";
    String usuario = "mysql.username";
    String password = "mysql.password";
    this.connection = new ConnectionMySQL(config.getString(host),
    config.getInt(port),
    config.getString(database),
    config.getString(usuario),
    config.getString(password));  

    // REGISTRO DE COMANDOS Y CONSTRUCTOR JDA
    registerCommands();

    Main.instance = this;
    
    System.out.println("zDiscord plugin is online");
    saveDefaultConfig();
}

The full error is this: https://pastebin.com/Qq9r8XTv

**Caused by:** *com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure* — Robert Harvey, Jul 28 '22 at 20:56
**Caused by:** *java.net.ConnectException: Connection refused* — Robert Harvey, Jul 28 '22 at 20:57
That's what I'm trying to figure out, but could you tell me the most common things this happens for or something? — Abel Albor, Jul 28 '22 at 21:58
I would start by making sure the server is responding to requests (possibly by using some other utility such as MySQL Workbench), and then checking your connection string to make sure that it is absolutely correct in every detail. — Robert Harvey, Jul 28 '22 at 22:11
I was able to fix it, it happened that in the configuration file I put the port in quotes, thank you very much! — Abel Albor, Jul 30 '22 at 21:39

score -1 · Answer 1 · answered Jul 30 '22 at 04:16

-1

you can try as below:

 Connection connection = DriverManager.getConnection("jdbc:mysql://"+host+":"+puerto+"/"+database,usuario,password);

instead of this.connection=DriverManager.getConnection("jdbc:mysql://"+host+":"+puerto+"/"+database,usuario,password);

answered Jul 30 '22 at 04:16

ritu mansata

77
2
13

it was nothing in the code, I was entering the connection data wrong, add the port in quotes in the configuration file, anyway thank you very much – Abel Albor Jul 30 '22 at 21:40

It won't let me connect to the database from my plugin: "Cannot invoke "java.sql.Connection.prepareStatement(String)" because "connection" is null"

1 Answers1