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This guide walks you through the process of connecting to a MySQL database using the SQL Editor’s login interface.

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Connection Form

The login view (View.java) provides a comprehensive form for establishing database connections with the following fields:

Server

Select the MySQL server address. Defaults include localhost and 127.0.0.1.

User

Enter your MySQL username for authentication.

Password

Provide the password associated with your MySQL user account.

Database

Choose the target database from the dropdown list.

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Step-by-Step Connection Process

1

Enter Server Credentials

Fill in the Server, User, and Password fields in the login form. The server field allows you to select from predefined options or enter a custom address.
// The View class retrieves these values:
public String getUsuario() { return txtUsuario.getText().trim(); }
public String getPassword() { return new String(txtPassword.getPassword()).trim(); }
public String getServidor() { return (String) cmbServidores.getSelectedItem(); }
2

Fetch Available Databases

Click the Actualizar (Refresh) button to retrieve all available databases from the server. This calls Model.obtenerTodasLasBasesDatos().
// Controller.java - Line 115
return modelo.obtenerTodasLasBasesDatos(
    loginView.getServidor(),
    loginView.getUsuario(),
    loginView.getPassword()
);
The application automatically filters out system databases (information_schema, mysql, performance_schema, sys) from the list.
3

Select a Database

Once the databases load successfully, choose your target database from the dropdown menu. The dropdown is populated with the fetched database names:
// View.java - Line 213
public void setBasesDatos(List<String> bases) {
    cbBasesDatos.removeAllItems();
    bases.forEach(cbBasesDatos::addItem);
}
4

Connect

Click the Conectar (Connect) button to establish the connection. The application validates your inputs and attempts to connect:
// Controller.java - Line 155
modelo.conectar(
    loginView.getServidor(),
    loginView.getBaseDatosSeleccionada(),
    loginView.getUsuario(),
    loginView.getPassword()
);
Upon successful connection, the SQL Editor window opens, and the available tables are loaded automatically.

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Validation and Error Handling

The application performs comprehensive validation before attempting to connect:

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Field Validation

The validarCamposLogin() method in Controller.java checks: 
// Controller.java - Line 85
if(loginView.getUsuario().isEmpty()) {
    loginView.mostrarError("El usuario es requerido");
    return false;
}
Ensures the username field is not empty.
// Controller.java - Line 90
if(loginView.getPassword().isEmpty()) {
    loginView.mostrarError("La contraseña es requerida");
    return false;
}
Ensures the password field is not empty.
// Controller.java - Line 95
if(!soloCredenciales && loginView.getBaseDatosSeleccionada() == null) {
    loginView.mostrarError("Debe seleccionar una base de datos");
    return false;
}
Ensures a database is selected before connecting.

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Error Messages

If the connection fails, error messages are displayed in the status label:
// Controller.java - Line 180
loginView.mostrarError("Error de conexión: " + ex.getMessage());
Common errors include:
  • Invalid credentials
  • Server not reachable
  • Database access denied
  • Network connectivity issues

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Connection URL Format

The application constructs MySQL JDBC connection URLs in the following format: 
// Model.java - Line 54
"jdbc:mysql://" + host + ":3306/" + database + "?useSSL=false"
The default port 3306 is used for all MySQL connections. SSL is disabled by default with the useSSL=false parameter.

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Background Processing

All connection operations are performed asynchronously using SwingWorker to prevent UI freezing: 
// Controller.java - Line 112
SwingWorker<List<String>, Void> worker = new SwingWorker<>() {
    @Override
    protected List<String> doInBackground() throws Exception {
        return modelo.obtenerTodasLasBasesDatos(
            loginView.getServidor(),
            loginView.getUsuario(),
            loginView.getPassword()
        );
    }
};
During connection operations, the interface is temporarily disabled to prevent multiple simultaneous connection attempts:
// View.java - Line 239
public void bloquearInterfaz(boolean bloquear) {
    cmbServidores.setEnabled(!bloquear);
    txtUsuario.setEnabled(!bloquear);
    txtPassword.setEnabled(!bloquear);
    // ... additional components
}

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Success Confirmation

When databases are successfully fetched, you’ll see a confirmation dialog: 
// Controller.java - Line 132
JOptionPane.showMessageDialog(loginView,
    "Bases de datos actualizadas correctamente",
    "Éxito", JOptionPane.INFORMATION_MESSAGE);
After a successful connection, the login window closes and the SQL Editor interface appears with:
  • The connected database name displayed
  • A list of available tables
  • The SQL query editor ready for use

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Next Steps

Writing Queries

Learn how to write and execute SQL queries

Managing Connections

Switch databases and manage your active connection

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