DatabaseConnection.java

package database;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

/**
 * DatabaseConnection.java - Manages MySQL database connections
 * 
 * Handles:
 * - Connection establishment
 * - Driver loading
 * - Connection pooling ready (can be extended with HikariCP)
 * - Error handling
 * 
 * Best Practice: Centralized connection management prevents code duplication
 */
public class DatabaseConnection {
    
    // Database connection parameters
    private static final String DB_URL = "jdbc:mysql://localhost:3306/library_management";
    private static final String DB_USER = "root";
    private static final String DB_PASSWORD = "root";  // Change to your MySQL password
    private static final String DB_DRIVER = "com.mysql.cj.jdbc.Driver";
    
    // Connection timeout
    private static final int CONNECTION_TIMEOUT = 30; // seconds
    
    /**
     * Static block to load MySQL driver at class loading time
     * Throws exception if driver is not found
     */
    static {
        try {
            Class.forName(DB_DRIVER);
            System.out.println("✓ MySQL Driver loaded successfully");
        } catch (ClassNotFoundException e) {
            System.err.println("✗ MySQL Driver not found: " + e.getMessage());
            System.err.println("Add mysql-connector-java JAR to classpath");
        }
    }
    
    /**
     * Gets a new database connection
     * 
     * @return Connection object to MySQL database
     * @throws SQLException if connection fails
     */
    public static Connection getConnection() throws SQLException {
        try {
            Connection conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
            return conn;
        } catch (SQLException e) {
            System.err.println("✗ Database connection failed: " + e.getMessage());
            throw new SQLException("Unable to connect to database", e);
        }
    }
    
    /**
     * Tests the database connection
     * Useful for debugging connection issues
     * 
     * @return true if connection successful, false otherwise
     */
    public static boolean testConnection() {
        try (Connection conn = getConnection()) {
            if (conn.isValid(5)) { // 5 second timeout
                System.out.println("✓ Database connection test passed");
                return true;
            }
        } catch (SQLException e) {
            System.err.println("✗ Connection test failed: " + e.getMessage());
        }
        return false;
    }
    
    /**
     * Closes a database connection safely
     * Handles null connection gracefully
     * 
     * @param conn Connection to close
     */
    public static void closeConnection(Connection conn) {
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                System.err.println("Error closing connection: " + e.getMessage());
            }
        }
    }
}