qt实现sqlite3连接池

在 Qt 中实现 SQLite3 连接池需要以下步骤：

1. 创建一个 SQLite3 连接类，其中包含打开 SQLite3 数据库的函数和关闭数据库的函数。

// sqliteconnection.h
#ifndef SQLITECONNECTION_H
#define SQLITECONNECTION_H

#include <QString>
#include <QSqlDatabase>
#include <QSqlError>

class SQLiteConnection
{
public:
    static bool open(QString path);
    static void close();
    static QSqlDatabase getConnection();

private:
    static QSqlDatabase db;
};

#endif // SQLITECONNECTION_H

// sqliteconnection.cpp
#include "sqliteconnection.h"

QSqlDatabase SQLiteConnection::db;

bool SQLiteConnection::open(QString path)
{
    db = QSqlDatabase::addDatabase("QSQLITE");
    db.setDatabaseName(path);

    if (!db.open()) {
        qDebug() << "Error: connection with database failed";
        qDebug() << db.lastError().text();
        return false;
    }

    qDebug() << "Database: connection ok";
    return true;
}

void SQLiteConnection::close()
{
    db.close();
}

QSqlDatabase SQLiteConnection::getConnection()
{
    return db;
}

2. 创建一个 SQLite3 连接池类，其中包含获取连接和释放连接的函数。

// sqlitepool.h
#ifndef SQLITEPOOL_H
#define SQLITEPOOL_H

#include <QObject>
#include <QSqlDatabase>
#include <QMutex>
#include <QQueue>

class SQLitePool : public QObject
{
    Q_OBJECT
public:
    static SQLitePool& getInstance();
    QSqlDatabase getConnection();
    void releaseConnection(QSqlDatabase conn);

private:
    SQLitePool(QObject* parent = nullptr);
    ~SQLitePool();
    SQLitePool(const SQLitePool&) = delete;
    SQLitePool& operator=(const SQLitePool&) = delete;

    QMutex mutex;
    QQueue<QSqlDatabase> pool;
};

#endif // SQLITEPOOL_H

// sqlitepool.cpp
#include "sqlitepool.h"
#include "sqliteconnection.h"

SQLitePool::SQLitePool(QObject* parent)
    : QObject(parent)
{
}

SQLitePool::~SQLitePool()
{
    QMutexLocker locker(&mutex);
    while (!pool.isEmpty()) {
        QSqlDatabase conn = pool.dequeue();
        conn.close();
    }
    QSqlDatabase::removeDatabase("qt_sql_default_connection");
}

SQLitePool& SQLitePool::getInstance()
{
    static SQLitePool instance;
    return instance;
}

QSqlDatabase SQLitePool::getConnection()
{
    QMutexLocker locker(&mutex);
    if (pool.isEmpty()) {
        return SQLiteConnection::getConnection();
    }

    return pool.dequeue();
}

void SQLitePool::releaseConnection(QSqlDatabase conn)
{
    QMutexLocker locker(&mutex);
    if (conn.isOpen()) {
        pool.enqueue(conn);
    }
}

3. 在应用程序中使用连接池。

// main.cpp
#include <QCoreApplication>
#include <QDebug>
#include <QSqlQuery>
#include "sqlitepool.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    SQLitePool& pool = SQLitePool::getInstance();
    if (!SQLiteConnection::open("test.db")) {
        return -1;
    }

    QSqlDatabase conn1 = pool.getConnection();
    QSqlQuery query1(conn1);
    query1.exec("CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT)");

    QSqlDatabase conn2 = pool.getConnection();
    QSqlQuery query2(conn2);
    query2.exec("INSERT INTO users (name) VALUES ('Alice')");

    QSqlDatabase conn3 = pool.getConnection();
    QSqlQuery query3(conn3);
    query3.exec("SELECT * FROM users");

    while (query3.next()) {
        qDebug() << query3.value(0).toInt() << query3.value(1).toString();
    }

    pool.releaseConnection(conn2);

    QSqlDatabase conn4 = pool.getConnection();
    QSqlQuery query4(conn4);
    query4.exec("INSERT INTO users (name) VALUES ('Bob')");

    pool.releaseConnection(conn4);
    pool.releaseConnection(conn1);
    pool.releaseConnection(conn3);

    SQLiteConnection::close();

    return a.exec();
}

以上就是实现 SQLite3 连接池的基本步骤，你可以根据自己的需求进行修改和扩展。