Java 連接 MySQL 數據庫實戰指南：環境配置與 CRUD 示例

快速配置清單

• JDK：安裝並配置 JAVA_HOME、PATH。
• MySQL：安裝服務，記住 root 密碼。
• 驅動包：下載 mysql-connector-java，放入項目 WEB-INF/lib 或 Maven 依賴：
  <dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.33</version></dependency>

數據庫初始化腳本

CREATE DATABASE IF NOT EXISTS demo_db CHARACTER SET utf8mb4;
USE demo_db;
CREATE TABLE IF NOT EXISTS users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL UNIQUE,
    email VARCHAR(100),
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
INSERT INTO users (username, email) VALUES ('alice', 'alice@example.com'), ('bob', 'bob@example.com');

通用 JDBC 工具類

public class JdbcUtil {
    private static final String URL = "jdbc:mysql://localhost:3306/demo_db?useUnicode=true&characterEncoding=utf8&useSSL=false&serverTimezone=Asia/Shanghai";
    private static final String USER = "root";
    private static final String PASS = "123456";

    static {
        try { Class.forName("com.mysql.cj.jdbc.Driver"); }
        catch (ClassNotFoundException e) { throw new ExceptionInInitializerError(e); }
    }

    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(URL, USER, PASS);
    }

    public static void close(Connection c, Statement s, ResultSet r) {
        try { if (r != null) r.close(); } catch (SQLException ignored) {}
        try { if (s != null) s.close(); } catch (SQLException ignored) {}
        try { if (c != null) c.close(); } catch (SQLException ignored) {}
    }
}

CRUD 操作示例

public class UserDao {
    public void insert(User u) {
        String sql = "INSERT INTO users(username, email) VALUES(?, ?)";
        try (Connection c = JdbcUtil.getConnection();
             PreparedStatement ps = c.prepareStatement(sql)) {
            ps.setString(1, u.getUsername());
            ps.setString(2, u.getEmail());
            ps.executeUpdate();
        } catch (SQLException e) { e.printStackTrace(); }
    }

    public List<User> selectAll() {
        List<User> list = new ArrayList<>();
        String sql = "SELECT * FROM users";
        try (Connection c = JdbcUtil.getConnection();
             PreparedStatement ps = c.prepareStatement(sql);
             ResultSet rs = ps.executeQuery()) {
            while (rs.next()) {
                User u = new User();
                u.setId(rs.getInt("id"));
                u.setUsername(rs.getString("username"));
                u.setEmail(rs.getString("email"));
                list.add(u);
            }
        } catch (SQLException e) { e.printStackTrace(); }
        return list;
    }
    // update、delete 同理使用 PreparedStatement 防注入
}

最佳實踐提醒

1. 優先使用 PreparedStatement 防止 SQL 注入並提升性能。
2. 資源關閉採用 try-with-resources（JDK 7+）自動管理。
3. 生產環境必須接入連接池，避免頻繁創建銷毀連接。
4. 異常處理建議拋出自定義業務異常，由上層統一處理。