Features Reference - MySQL SQL Editor

Overview

This reference documents all features available in the MySQL SQL Editor, including database connection management, query execution, result handling, and asynchronous operations.

Core Features

Database Connection Management

Source: Controller.java:149-186, Model.java:53-59

Connection Process

The application establishes connections using JDBC with the following parameters:Connection URL Format:

jdbc:mysql://{host}:3306/{database}?useSSL=false

Supported Servers:

localhost
127.0.0.1
Custom server addresses (via combo box)

Validation

Pre-Connection Checks (Controller.java:84-101):

Username is not empty
Password is not empty
Database is selected (for connection)

Error Messages:

“El usuario es requerido” - Username required
“La contraseña es requerida” - Password required
“Debe seleccionar una base de datos” - Database selection required

Async Execution

Connection operations use SwingWorker to prevent UI freezing:

SwingWorker<Boolean, Void> worker = new SwingWorker<>() {
    @Override
    protected Boolean doInBackground() throws Exception {
        modelo.conectar(
            loginView.getServidor(),
            loginView.getBaseDatosSeleccionada(),
            loginView.getUsuario(),
            loginView.getPassword()
        );
        return true;
    }
};

Post-Connection Actions

After successful connection:

Database name is set in editor view (SqlEditorView.java:291-299)
Table list is populated (Controller.java:172-173)
Login view is hidden
Editor view is displayed

Connection state is stored in Model.conexion (Model.java:14) and reused for all subsequent queries.

Database Discovery

Source: Controller.java:107-143, Model.java:26-42

Fetching Available Databases

The “Actualizar” button retrieves all accessible databases from the MySQL server.SQL Query:

SHOW DATABASES

System Database Filtering (Model.java:36-38):The following system databases are excluded from the list:

information_schema
mysql
performance_schema
sys

Filter Regex:

if (!nombreBD.matches("information_schema|mysql|performance_schema|sys")) {
    basesDatos.add(nombreBD);
}

Empty Database Handling

If no user databases are found:

Error message: “No se encontraron bases de datos”
Combo box remains empty
User must create a database via external tools

Success Feedback

On successful retrieval:

Combo box is populated with database names
Success dialog: “Bases de datos actualizadas correctamente”

This operation requires valid credentials but does NOT establish a persistent connection. It creates a temporary connection that is closed immediately after fetching the database list.

SQL Query Execution

Source: Controller.java:234-264, Model.java:101-154

Query Types

The application handles two types of SQL queries:

1. SELECT Queries

Detection: Model.java:106

if (trimmedQuery.startsWith("select"))

Process:

Execute query using Statement.executeQuery()
Extract metadata from ResultSetMetaData
Create DefaultTableModel with column names
Iterate through result set and add rows
Display results in tblResultados

Column Extraction (Model.java:108-113):

ResultSetMetaData meta = rs.getMetaData();
int columnas = meta.getColumnCount();

for (int i = 1; i <= columnas; i++) {
    modelo.addColumn(meta.getColumnName(i));
}

2. Modification Queries

Types: INSERT, UPDATE, DELETE, CREATE, ALTER, DROP, TRUNCATEProcess:

Execute using Statement.executeUpdate()
Get affected row count
Extract table name from query (Model.java:163-191)
If table found, display updated table contents
Otherwise, display affected row count

Table Name Extraction (Model.java:163-191):Supports the following patterns:

CREATE TABLE {table_name}
INSERT INTO {table_name}
UPDATE {table_name}
DELETE FROM {table_name}
TRUNCATE TABLE {table_name}

Example:

// Query: "INSERT INTO users VALUES (1, 'John')"
// Result: Displays updated 'users' table contents

// Query: "DROP TABLE old_data"
// Result: Displays "Filas afectadas: 0"

Pre-Execution Validation

Check: Query is not empty (Controller.java:235-239)

if(editorView.getConsulta().trim().isEmpty()) {
    JOptionPane.showMessageDialog(editorView,
        "Ingrese una consulta SQL",
        "Advertencia", JOptionPane.WARNING_MESSAGE);
    return;
}

Async Execution

All queries execute in background threads using SwingWorker<DefaultTableModel, Void>:

SwingWorker<DefaultTableModel, Void> worker = new SwingWorker<>() {
    @Override
    protected DefaultTableModel doInBackground() throws Exception {
        return modelo.ejecutarConsulta(editorView.getConsulta());
    }
    
    @Override
    protected void done() {
        // Update UI with results
    }
};

The query trimming and lowercase conversion happens in the Model layer, not the Controller, ensuring consistent processing.

Result Display

Source: SqlEditorView.java:263-268, Controller.java:250-253

Table Model Update

Results are displayed using Swing’s DefaultTableModel:

editorView.setResultados(modelo);

Column Width Adjustment

Default Width: 150 pixels per column (SqlEditorView.java:265-267)

for (int i = 0; i < tblResultados.getColumnModel().getColumnCount(); i++) {
    tblResultados.getColumnModel().getColumn(i).setPreferredWidth(150);
}

Row Data Handling

Null Values: Displayed as “null” (handled by ResultSet.getObject())Data Types: All column types are preserved from the database:

Integers → Integer objects
Strings → String objects
Dates → Date/Timestamp objects
Decimals → BigDecimal objects

System Messages

Success Message:

editorView.setMensajeSistema("Consulta ejecutada correctamente");

Error Message:

editorView.setMensajeSistema("Error: " + ex.getMessage());

Modification Result:

Filas afectadas: {count}

The results table (tblResultados) uses setFillsViewportHeight(true) to expand to fill available space, providing a better viewing experience for small result sets.

Table Browsing

Source: Controller.java:192-212, Model.java:78-90

Table List Population

Method: Model.obtenerTablasDeBaseDatos()Process:

Get database metadata using Connection.getMetaData()
Get current catalog using Connection.getCatalog()
Query metadata for tables of type “TABLE”
Extract table names from result set

JDBC Metadata Query (Model.java:81-87):

DatabaseMetaData metaData = conexion.getMetaData();
String catalogoActual = conexion.getCatalog();
try (ResultSet rs = metaData.getTables(catalogoActual, null, "%", new String[]{"TABLE"})) {
    while (rs.next()) {
        tablas.add(rs.getString("TABLE_NAME"));
    }
}

Exclusions: Views, system tables, and temporary tables are not included

Refresh Functionality

The “Refrescar tablas” button re-fetches the table list (Controller.java:192-212):

editorView.getBtnRefrescarTablas().addActionListener(e -> refrescarTablas());

Use Cases:

After creating new tables
After dropping tables
When schema changes are made externally

Double-Click Quick Query

Source: SqlEditorView.java:146-156When a table is double-clicked, a SELECT query is auto-generated:

String consulta = "SELECT * FROM " + tablaSeleccionada + " LIMIT 100";
txtConsulta.setText(consulta);

Query Template:

SELECT * FROM {table_name} LIMIT 100

The LIMIT 100 clause prevents accidentally loading huge tables. Users can modify or remove this limit before executing.

Empty Table List Handling

If no tables exist:

Tooltip: “No se encontraron tablas”
List appears empty
No error dialog is shown

Asynchronous Operations

Source: Controller.java (all async methods)

SwingWorker Implementation

All long-running operations use SwingWorker to prevent UI freezing:

1. Database List Loading

Worker Type: SwingWorker<List<String>, Void>Source: Controller.java:112-142

SwingWorker<List<String>, Void> worker = new SwingWorker<>() {
    @Override
    protected List<String> doInBackground() throws Exception {
        return modelo.obtenerTodasLasBasesDatos(
            loginView.getServidor(),
            loginView.getUsuario(),
            loginView.getPassword()
        );
    }
    
    @Override
    protected void done() {
        loginView.bloquearInterfaz(false);
        try {
            List<String> bases = get();
            loginView.setBasesDatos(bases);
        } catch (Exception ex) {
            loginView.mostrarError("Error: " + ex.getMessage());
        }
    }
};

2. Database Connection

Worker Type: SwingWorker<Boolean, Void>Source: Controller.java:152-186

3. Query Execution

Worker Type: SwingWorker<DefaultTableModel, Void>Source: Controller.java:242-264

4. Table Refresh

Worker Type: SwingWorker<List<String>, Void>Source: Controller.java:193-212

UI Locking Pattern

All async operations follow this pattern:

// Before execution
loginView.bloquearInterfaz(true);

// Start worker
worker.execute();

// In done() method
loginView.bloquearInterfaz(false);

Benefits:

Prevents concurrent operations
Provides visual feedback (grayed-out controls)
Prevents invalid input during processing

Error Handling in Workers

All done() methods use try-catch to handle exceptions:

@Override
protected void done() {
    try {
        Result result = get(); // May throw ExecutionException
        // Process result
    } catch (Exception ex) {
        // Display error to user
    }
}

Never perform UI updates in doInBackground(). Always update UI components in the done() method on the Event Dispatch Thread.

Error Handling

Source: Controller.java (error handling blocks), Model.java (SQLException throws)

Exception Types

SQLException

Thrown By:

Model.obtenerTodasLasBasesDatos() - Invalid credentials, network errors
Model.conectar() - Connection failures, invalid database
Model.ejecutarConsulta() - Syntax errors, constraint violations
Model.desconectar() - Connection closing errors

Handling:

catch (Exception ex) {
    loginView.mostrarError("Error: " + ex.getMessage());
}

Error Display Methods

Method: View.mostrarError(String mensaje)Display: Red label below input fields (View.java:223-225)Common Messages:

“El usuario es requerido”
“La contraseña es requerida”
“Debe seleccionar una base de datos”
“Error: ”
“Error de conexión: ”
“No se encontraron bases de datos”

Editor View Errors

Method 1: SqlEditorView.setMensajeSistema(String mensaje)Display: Gray label above results tableMethod 2: JOptionPane.showMessageDialog()Display: Modal error dialogCommon Messages:

“Ingrese una consulta SQL” (Warning)
“Error en la consulta: ” (Error)
“Error al obtener tablas: ” (Error)
“Error al desconectar: ” (Error)

Query Validation Errors

Empty Query:

if(editorView.getConsulta().trim().isEmpty()) {
    JOptionPane.showMessageDialog(editorView,
        "Ingrese una consulta SQL",
        "Advertencia", JOptionPane.WARNING_MESSAGE);
    return;
}

Syntax Errors:

Caught from SQLException during execution
Displayed in both system message and error dialog
Result table is not modified

The application does not perform client-side SQL validation. All syntax and semantic errors are caught at execution time when MySQL processes the query.

Database Disconnection

Source: Controller.java:217-228, Model.java:66-70

Disconnect Process

Triggered by the “Cambiar BD” button with confirmation dialog:

int confirm = JOptionPane.showConfirmDialog(editorView,
    "¿Desea desconectarse y cambiar de base de datos?",
    "Confirmar",
    JOptionPane.YES_NO_OPTION);

if (confirm == JOptionPane.YES_OPTION) {
    desconectar();
}

Cleanup Steps

Close JDBC connection (Model.java:66-70):

if (conexion != null && !conexion.isClosed()) {
    conexion.close();
}

Reset editor view database status:

editorView.setBaseDeDatos(null);

Hide editor view, show login view:

editorView.setVisible(false);
loginView.setVisible(true);

State After Disconnection

Connection object is null
Editor view displays “Estado: No conectado”
Table list is not cleared (but is stale)
Query text is preserved
Results table is preserved

Previous credentials remain in the login form, allowing quick reconnection with the same or different settings.

UI State Management

Source: View.java:239-252

Interface Locking

Method: bloquearInterfaz(boolean bloquear)Purpose: Disable user input during async operationsAffected Components:

Server selector (cmbServidores)
Username field (txtUsuario)
Password field (txtPassword)
Database selector (cbBasesDatos)
Refresh button (btnActualizarBases)
Connect button (btnConectar)

Visual Changes:When locked (bloquear = true):

All components disabled
Background color changes to #F0F0F0 (light gray)

When unlocked (bloquear = false):

All components enabled
Background color restored to white

Usage Pattern:

loginView.bloquearInterfaz(true);  // Lock before async operation
worker.execute();                   // Start background task
// ... in worker.done() ...
loginView.bloquearInterfaz(false); // Unlock after completion

State Clearing

Method: View.limpiarEstado()Source: View.java:230-232Clears the error message label before new operations:

loginView.limpiarEstado();
validarCamposLogin(true);

Editor Clearing

Method: SqlEditorView.limpiar()Source: SqlEditorView.java:281-285Resets all editor components:

txtConsulta.setText("");
tblResultados.setModel(new DefaultTableModel());
lblMensajeSistema.setText(" ");

The “Limpiar” button only clears the editor content, not the connection state or table list.

Feature Matrix

Feature	Login View	Editor View	Async	Source
Database Discovery	✓		✓	`Controller.java:107-143`
Database Connection	✓		✓	`Controller.java:149-186`
SQL Execution		✓	✓	`Controller.java:234-264`
Table Browsing		✓	✓	`Controller.java:192-212`
Result Display		✓		`SqlEditorView.java:263-268`
Error Handling	✓	✓		Throughout
UI Locking	✓			`View.java:239-252`
Disconnection		✓		`Controller.java:217-228`
Quick Query		✓		`SqlEditorView.java:146-156`

Connection String Reference

Format

jdbc:mysql://{host}:3306/{database}?useSSL=false

Parameters

{host} - Server address (localhost, 127.0.0.1, or custom)
3306 - Default MySQL port (hardcoded)
{database} - Target database name (or empty for database discovery)
useSSL=false - Disables SSL for local development

Examples

Database Discovery:

jdbc:mysql://localhost:3306/?useSSL=false

Database Connection:

jdbc:mysql://localhost:3306/my_app_db?useSSL=false

The application does not support custom ports. All connections use port 3306.

Getting Started

User Guide

Architecture

Development

Reference

​Overview

​Core Features

​Connection Process

​Validation

​Async Execution

​Post-Connection Actions

​Fetching Available Databases

​Empty Database Handling

​Success Feedback

​Query Types

​1. SELECT Queries

​2. Modification Queries

​Pre-Execution Validation

​Async Execution

​Table Model Update

​Column Width Adjustment

​Row Data Handling

​System Messages

​Table List Population

​Refresh Functionality

​Double-Click Quick Query

​Empty Table List Handling

​SwingWorker Implementation

​1. Database List Loading

​2. Database Connection

​3. Query Execution

​4. Table Refresh

​UI Locking Pattern

​Error Handling in Workers

​Exception Types

​SQLException

​Error Display Methods

​Login View Errors

​Editor View Errors

​Query Validation Errors

​Disconnect Process

​Cleanup Steps

​State After Disconnection

​Interface Locking

​State Clearing

​Editor Clearing

​Feature Matrix

​Connection String Reference

​Format

​Parameters

​Examples

Build docs developers (and LLMs) love

Overview

Core Features

Connection Process

Validation

Async Execution

Post-Connection Actions

Fetching Available Databases

Empty Database Handling

Success Feedback

Query Types

1. SELECT Queries

2. Modification Queries

Pre-Execution Validation

Async Execution

Table Model Update

Column Width Adjustment

Row Data Handling

System Messages

Table List Population

Refresh Functionality

Double-Click Quick Query

Empty Table List Handling

SwingWorker Implementation

1. Database List Loading

2. Database Connection

3. Query Execution

4. Table Refresh

UI Locking Pattern

Error Handling in Workers

Exception Types

SQLException

Error Display Methods

Login View Errors

Editor View Errors

Query Validation Errors

Disconnect Process

Cleanup Steps

State After Disconnection

Interface Locking

State Clearing

Editor Clearing

Feature Matrix

Connection String Reference

Format

Parameters

Examples