Qt实战：使用QSqlDatabase连接MySQL，并实现增删改查
文章目录
- 一、创建数据表
- 二、连接MySQL数据库
- 三、封装成一个完整的轻量级 ORM 风格类
- 四、实现派生具体模型类
- 五、支持多线程连接池 + ORM + 事务封装
一、创建数据表
数据库名：
我们先创建一个数据库，名字叫 game_db：
CREATE DATABASE IF NOT EXISTS game_db DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;
USE game_db;
创建玩家表：players
CREATE TABLE players (player_id INT AUTO_INCREMENT PRIMARY KEY,username VARCHAR(32) NOT NULL UNIQUE,password_hash VARCHAR(64) NOT NULL,nickname VARCHAR(32),level INT DEFAULT 1,experience INT DEFAULT 0,gold INT DEFAULT 0,created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
插入 20 条玩家信息 SQL 语句：
INSERT INTO players (username, password_hash, nickname, level, experience, gold) VALUES
('user001', MD5('password1'), 'Knight001', 5, 1200, 500),
('user002', MD5('password2'), 'Mage002', 3, 800, 300),
('user003', MD5('password3'), 'Archer003', 7, 1800, 750),
('user004', MD5('password4'), 'Rogue004', 2, 400, 100),
('user005', MD5('password5'), 'Cleric005', 10, 3200, 1200),
('user006', MD5('password6'), 'Paladin006', 4, 950, 400),
('user007', MD5('password7'), 'Hunter007', 6, 1400, 600),
('user008', MD5('password8'), 'Druid008', 8, 2200, 900),
('user009', MD5('password9'), 'Monk009', 9, 2500, 1000),
('user010', MD5('password10'), 'Barbarian010', 1, 100, 50),
('user011', MD5('password11'), 'Warrior011', 5, 1300, 550),
('user012', MD5('password12'), 'Sorcerer012', 3, 700, 300),
('user013', MD5('password13'), 'Assassin013', 6, 1600, 650),
('user014', MD5('password14'), 'Priest014', 7, 1900, 800),
('user015', MD5('password15'), 'Ranger015', 2, 500, 200),
('user016', MD5('password16'), 'Berserker016', 4, 1100, 450),
('user017', MD5('password17'), 'Necromancer017', 8, 2300, 950),
('user018', MD5('password18'), 'Templar018', 9, 2700, 1100),
('user019', MD5('password19'), 'Shaman019', 10, 3000, 1250),
('user020', MD5('password20'), 'Witch020', 1, 200, 100);
表中结果如下所示：
二、连接MySQL数据库
database_manager.h
#ifndef DATABASEMANAGER_H
#define DATABASEMANAGER_H#include <QObject>
#include <QMutex>
#include <QSqlDatabase>
#include <QSqlError>enum DatabaseType {MySQL = 0,SQLite,PostgreSQL,// 可扩展更多类型
};typedef struct stConnectParams {DatabaseType dbType;QString strHostName;QString strDbName;QString strUserName;QString strPassword;QString strConnectionName;int port;
} ConnectParams;class DatabaseManager : public QObject
{Q_OBJECT
public:static DatabaseManager& instance();void initConnectionParams(const ConnectParams& connectParams);void initializeConnection();private:explicit DatabaseManager(QObject *parent = nullptr);~DatabaseManager();DatabaseManager(const DatabaseManager&) = delete;DatabaseManager& operator =(const DatabaseManager&) = delete;DatabaseManager(const DatabaseManager&&) = delete;DatabaseManager& operator =(const DatabaseManager&&) = delete;signals:private:ConnectParams m_connectParams;
};
database_manager.cpp
#include "database_manager.h"#include <QDebug>DatabaseManager::DatabaseManager(QObject *parent) : QObject(parent)
{}DatabaseManager::~DatabaseManager()
{}DatabaseManager& DatabaseManager::instance()
{static DatabaseManager instance;return instance;
}void DatabaseManager::initConnectionParams(const ConnectParams& connectParams)
{m_connectParams.dbType = connectParams.dbType;m_connectParams.strHostName = connectParams.strHostName;m_connectParams.strDbName = connectParams.strDbName;m_connectParams.strUserName = connectParams.strUserName;m_connectParams.strPassword = connectParams.strPassword;m_connectParams.strConnectionName = connectParams.strConnectionName;m_connectParams.port = connectParams.port;
}void DatabaseManager::initializeConnection()
{if (QSqlDatabase::contains(m_connectParams.strConnectionName)) {qDebug() << "db:" << m_connectParams.strConnectionName << "already connected";return;}QString strDriver;switch (m_connectParams.dbType) {case DatabaseType::SQLite:strDriver = "QSQLITE";break;case DatabaseType::MySQL:strDriver = "QMYSQL";break;case DatabaseType::PostgreSQL:strDriver = "QPSQL";break;}if (strDriver.isEmpty()) {qDebug() << "can't find driver";return;}QSqlDatabase db = QSqlDatabase::addDatabase(strDriver, m_connectParams.strConnectionName);if (m_connectParams.dbType == DatabaseType::SQLite) {db.setDatabaseName(m_connectParams.strDbName); // SQLite只需数据库文件路径} else {db.setConnectOptions("MYSQL_OPT_CONNECT_TIMEOUT=5;""MYSQL_OPT_READ_TIMEOUT=5;""MYSQL_OPT_WRITE_TIMEOUT=5;");db.setHostName(m_connectParams.strHostName);db.setPort(m_connectParams.port);db.setDatabaseName(m_connectParams.strDbName);db.setUserName(m_connectParams.strUserName);db.setPassword(m_connectParams.strPassword);}if (!db.open()) {qDebug() << "Database connection failed:" << db.lastError().text();} else {qDebug() << "Database connected successfully!";}
}三、封装成一个完整的轻量级 ORM 风格类
什么是ORM 模型类的？
ORM（Object-Relational Mapping）模型类的作用，是将数据库中的表与 C++（或其他语言）中的类进行映射和封装，让你能像操作普通对象那样操作数据库数据，避免直接拼接 SQL 字符串，提高代码的可读性、可维护性、安全性和抽象性。
ORM 模型类的作用总结如下：
3.1 表结构 → 类结构
ORM 会把数据库表（如 users）映射成一个类（如 User），表字段对应类成员或字段名：
// 数据库表字段
// id | name | age// ORM类字段
QVariantMap row;
row["id"] = 1;
row["name"] = "Alice";
row["age"] = 30;
3.2 简化 SQL 操作
让你写这样的代码：
userModel.insert({{"name", "Tom"}, {"age", 25}});
而不需要写繁琐的 SQL：
INSERT INTO users (name, age) VALUES ('Tom', 25);
目标功能：
- 封装成类 OrmModel 或基类 OrmBase
- 支持设置数据库连接、表名
- 支持 select / insert / update / delete 等基础操作
- 使用 QVariantMap 传入/返回数据
- ORM风格：调用 model.select(…) 而不是手写 SQL 字符串
类定义：OrmBase
#ifndef DBORMBASE_H
#define DBORMBASE_H#include <QObject>
#include <QSqlDatabase>
#include <QVariantMap>
#include <QVariantList>class DbOrmBase : public QObject
{Q_OBJECT
public:explicit DbOrmBase(const QString &tableName, const QString &connectionName);~DbOrmBase();// CRUDQVariantList select(const QString &strWhereClause = "", const QStringList &columns = {});bool insert(const QVariantMap &values);bool update(const QVariantMap &values, const QString &strWhereClause);bool remove(const QString &strWhereClause);private:bool isConnected() const;private:QString m_tableName;QString m_connectionName;QSqlDatabase m_db; // 保存数据库实例
};#endif // DBORMBASE_H
类实现：OrmBase.cpp
#include "OrmBase.h"
#include <QSqlQuery>
#include <QSqlError>
#include <QSqlRecord>
#include <QDebug>OrmBase::OrmBase(const QString &tableName, const QString &connectionName): m_tableName(tableName), m_connectionName(connectionName)
{}QVariantList OrmBase::select(const QString &whereClause, const QStringList &columns)
{QVariantList results;QSqlDatabase db = QSqlDatabase::database(m_connectionName);if (!db.isOpen()) {qDebug() << "Database not open";return results;}QString columnStr = columns.isEmpty() ? "*" : columns.join(", ");QString sql = QString("SELECT %1 FROM %2").arg(columnStr, m_tableName);if (!whereClause.trimmed().isEmpty()) {sql += " WHERE " + whereClause;}QSqlQuery query(db);if (!query.exec(sql)) {qDebug() << "Select failed:" << query.lastError().text();return results;}while (query.next()) {QVariantMap row;QSqlRecord rec = query.record();for (int i = 0; i < rec.count(); ++i) {row[rec.fieldName(i)] = query.value(i);}results << row;}return results;
}bool OrmBase::insert(const QVariantMap &values)
{QSqlDatabase db = QSqlDatabase::database(m_connectionName);if (!db.isOpen()) return false;QStringList columns, placeholders;QVariantList bindValues;for (auto it = values.begin(); it != values.end(); ++it) {columns << it.key();placeholders << "?";bindValues << it.value();}QString sql = QString("INSERT INTO %1 (%2) VALUES (%3)").arg(m_tableName).arg(columns.join(", ")).arg(placeholders.join(", "));QSqlQuery query(db);query.prepare(sql);for (const QVariant &val : bindValues) {query.addBindValue(val);}if (!query.exec()) {qDebug() << "Insert failed:" << query.lastError().text();return false;}return true;
}bool OrmBase::update(const QVariantMap &values, const QString &whereClause)
{QSqlDatabase db = QSqlDatabase::database(m_connectionName);if (!db.isOpen()) return false;QStringList sets;QVariantList bindValues;for (auto it = values.begin(); it != values.end(); ++it) {sets << QString("%1 = ?").arg(it.key());bindValues << it.value();}QString sql = QString("UPDATE %1 SET %2").arg(m_tableName, sets.join(", "));if (!whereClause.trimmed().isEmpty()) {sql += " WHERE " + whereClause;}QSqlQuery query(db);query.prepare(sql);for (const QVariant &val : bindValues) {query.addBindValue(val);}if (!query.exec()) {qDebug() << "Update failed:" << query.lastError().text();return false;}return true;
}bool OrmBase::remove(const QString &whereClause)
{QSqlDatabase db = QSqlDatabase::database(m_connectionName);if (!db.isOpen()) return false;QString sql = QString("DELETE FROM %1").arg(m_tableName);if (!whereClause.trimmed().isEmpty()) {sql += " WHERE " + whereClause;}QSqlQuery query(db);if (!query.exec(sql)) {qDebug() << "Delete failed:" << query.lastError().text();return false;}return true;
}
使用示例：
#include <QCoreApplication>
#include <QDebug>
#include <QDateTime>#include "database_manager.h"
#include "db_ormbase.h"int main(int argc, char *argv[])
{QCoreApplication a(argc, argv);ConnectParams connectParams;connectParams.dbType = DatabaseType::MySQL;connectParams.strHostName = "localhost";connectParams.strDbName = "game_db";connectParams.strUserName = "root";connectParams.strPassword = "root";connectParams.strConnectionName = "user_game";connectParams.port = 3306;DatabaseManager::instance().initConnectionParams(connectParams);DatabaseManager::instance().initializeConnection();DbOrmBase userModel("players", "user_game");QVariantList playerList = userModel.select("experience > 1000");for (const QVariant &playerVar : playerList) {QVariantMap playerMap = playerVar.toMap();int playerId = playerMap.value("player_id").toInt();QString username = playerMap.value("username").toString();QString nickname = playerMap.value("nickname").toString();int level = playerMap.value("level").toInt();int experience = playerMap.value("experience").toInt();int gold = playerMap.value("gold").toInt();QString passwordHash = playerMap.value("password_hash").toString();QDateTime createdAt = playerMap.value("created_at").toDateTime();// 可以进行打印、显示、或保存到类对象中qDebug() << "ID:" << playerId<< "用户名:" << username<< "昵称:" << nickname<< "等级:" << level<< "经验:" << experience<< "金币:" << gold<< "密码Hash:" << passwordHash<< "创建时间:" << createdAt.toString(Qt::ISODate);}return a.exec();
}
输出结果：
四、实现派生具体模型类
为什么要派生？
虽然 OrmBase 已支持通用 CRUD，但派生后的 UserModel 能实现：
- 指定固定表名（如 players）
- 添加和 players 表相关的专属函数（如 getAdultUsers()、findByName()）
- 让调用更具语义：UserModel user; user.insert(…)
创建 UserModel 类
UserModel.h
#ifndef USERMODEL_H
#define USERMODEL_H#include "OrmBase.h"class UserModel : public OrmBase
{
public:explicit UserModel(const QString &connectionName = "default");// 自定义业务函数QVariantList getAdultUsers();QVariantMap findById(int id);QVariantList findByName(const QString &name);
};#endif // USERMODEL_H
UserModel.cpp
#include "UserModel.h"UserModel::UserModel(const QString &connectionName): OrmBase("players", connectionName) // 固定表名为 users
{}// 查询年龄 >= 18 的用户
QVariantList UserModel::getAdultUsers()
{return select("experience >= 1000", {"player_id", "username", "experience"});
}// 查询某个 ID 的用户（返回一行）
QVariantMap UserModel::findById(int id)
{auto results = select(QString("player_id = %1").arg(id));return results.isEmpty() ? QVariantMap() : results.first().toMap();
}// 查询某个名字的所有用户
QVariantList UserModel::findByName(const QString &name)
{QString clause = QString("username = '%1'").arg(name.replace("'", "''")); // 简单防注入return select(clause);
}
五、支持多线程连接池 + ORM + 事务封装
将构建以下组件：
+-------------------------+
| DBConnectionPool | 线程安全连接池类（单例）
+-------------------------+
| OrmBase | ORM 基类（封装表操作 + 自动获取线程连接）
+-------------------------+
| OrmManager | 管理多个模型，支持事务封装
+-------------------------+
| XxxModel : OrmBase | 表模型（如 UserModel）
+-------------------------+
5.1 线程安全数据库连接池：DBConnectionPool
DBConnectionPool.h
#ifndef DBCONNECTIONPOOL_H
#define DBCONNECTIONPOOL_H#include <QSqlDatabase>
#include <QMutex>
#include <QMap>
#include <QThreadStorage>class DBConnectionPool
{
public:static DBConnectionPool &instance();void init(const QString &driver,const QString &host,int port,const QString &dbName,const QString &user,const QString &password,int maxConn = 10);QSqlDatabase getConnection();void closeAll();private:DBConnectionPool() = default;Q_DISABLE_COPY(DBConnectionPool)QString m_driver, m_host, m_dbName, m_user, m_password;int m_port = 3306;int m_maxConn = 10;QMutex m_mutex;int m_connIndex = 0;QThreadStorage<QString> m_threadConnName;
};#endif // DBCONNECTIONPOOL_H
DBConnectionPool.cpp
#include "DBConnectionPool.h"
#include <QSqlDatabase>
#include <QSqlError>
#include <QDebug>DBConnectionPool &DBConnectionPool::instance()
{static DBConnectionPool pool;return pool;
}void DBConnectionPool::init(const QString &driver,const QString &host,int port,const QString &dbName,const QString &user,const QString &password,int maxConn)
{m_driver = driver;m_host = host;m_port = port;m_dbName = dbName;m_user = user;m_password = password;m_maxConn = maxConn;
}QSqlDatabase DBConnectionPool::getConnection()
{if (!m_threadConnName.hasLocalData()) {QMutexLocker locker(&m_mutex);QString connName = QString("conn_%1").arg(++m_connIndex);m_threadConnName.setLocalData(connName);QSqlDatabase db = QSqlDatabase::addDatabase(m_driver, connName);db.setHostName(m_host);db.setPort(m_port);db.setDatabaseName(m_dbName);db.setUserName(m_user);db.setPassword(m_password);db.setConnectOptions("MYSQL_OPT_CONNECT_TIMEOUT=5;""MYSQL_OPT_RECONNECT=1");if (!db.open()) {qCritical() << "Failed to open DB:" << db.lastError().text();}}return QSqlDatabase::database(m_threadConnName.localData());
}void DBConnectionPool::closeAll()
{QMutexLocker locker(&m_mutex);for (int i = 1; i <= m_connIndex; ++i) {QString name = QString("conn_%1").arg(i);if (QSqlDatabase::contains(name)) {QSqlDatabase::removeDatabase(name);}}m_connIndex = 0;
}
5.2 ORM 基类 OrmBase（使用连接池）
class OrmBase
{
public:OrmBase(const QString &tableName);virtual ~OrmBase() = default;bool insert(const QVariantMap &values);QVariantList select(const QString &whereClause = "", const QStringList &columns = {});bool update(const QVariantMap &values, const QString &whereClause);bool remove(const QString &whereClause);QSqlDatabase db() const;protected:QString m_tableName;
};
关键点：OrmBase 中不再保存 QSqlDatabase 实例，而是每次从线程池中获取：
QSqlDatabase OrmBase::db() const
{return DBConnectionPool::instance().getConnection();
}
5.3 事务封装类 OrmManager
用于封装如下逻辑：
- beginTransaction()
- commit()
- rollback()
class OrmManager
{
public:static bool beginTransaction();static bool commit();static bool rollback();
};实现：
bool OrmManager::beginTransaction()
{QSqlDatabase db = DBConnectionPool::instance().getConnection();return db.transaction();
}bool OrmManager::commit()
{QSqlDatabase db = DBConnectionPool::instance().getConnection();return db.commit();
}bool OrmManager::rollback()
{QSqlDatabase db = DBConnectionPool::instance().getConnection();return db.rollback();
}
5.4 使用示例：线程内事务 + 多表操作
DBConnectionPool::instance().init("QMYSQL", "127.0.0.1", 3306, "testdb", "root", "123456");UserModel user;
OrderModel order;OrmManager::beginTransaction();
bool ok1 = user.insert({{"name", "Tom"}});
bool ok2 = order.insert({{"user_id", 1}, {"amount", 200.0}});
if (ok1 && ok2)OrmManager::commit();
elseOrmManager::rollback();
5.5 线程使用示例（多线程安全）
QtConcurrent::run([](){UserModel u;u.insert({{"name", "ThreadUser"}});
});