记录一下QSqlDatabase数据库的单例类

用于存界面一个数据库表，目前只有一个数据库存了一个IP地址

QSqlDatabase类的sqlite数据库在Qt的项目工程里反复使用，使用单例加禁止拷贝构造，加互斥锁保证线程安全

头文件

#ifndef SQLITEDB_H
#define SQLITEDB_H

#include <QObject>
#include <QSqlDatabase>
#include <QSqlQuery>
#include <QSqlError>
#include <QDir>
#include <QApplication>
#include <QDebug>
#include <QMutex>
#include <QMutexLocker>



/* "OvenIPTable" (Id INTEGER PRIMARY KEY AUTOINCREMENT,OvenIP TEXT NOT NULL); // Id一直为1*/


class sqliteDB : public QObject
{
    Q_OBJECT
public:
    static sqliteDB* getInstance();
    QSqlDatabase& getDatabase();
    bool initDB();

    bool createSettingConfigTable();  //创建设置配置表
    QString getOvenIPAddress();       //获取设置配置
    bool updateOvenIPAddress(QString IPAddress);//更新设置配置表

signals:
    void sig_logInfo(QString info);

private :
    sqliteDB();
    ~sqliteDB();

    sqliteDB(const sqliteDB&) = delete; //禁止拷贝构造
    sqliteDB& operator=(const sqliteDB&) = delete; //禁止赋值操作

    static sqliteDB* instance;
    QMutex mutex;
    QSqlDatabase db;

    QString m_sDBName;
    QString m_sDBPath;
};

#endif // SQLITEDB_H

实现

#include "sqliteDB.h"

// 静态成员初始化
sqliteDB* sqliteDB::instance = nullptr;

sqliteDB::sqliteDB()
    : QObject(), db(QSqlDatabase::addDatabase("QSQLITE", "OvenIPTable"))
{
    m_sDBName = "entryStation.db";
    m_sDBPath = QDir::currentPath()+"/res/db";
    if(initDB())
    {
        qDebug() << "OvenIPTable数据库连接成功";
    }
}

sqliteDB::~sqliteDB()
{

}

sqliteDB* sqliteDB::getInstance()
{
    if(!instance)
    {
        instance = new sqliteDB();
    }
    return instance;
}

QSqlDatabase& sqliteDB::getDatabase()
{
    if(!db.isOpen())
    {
        if(!initDB())
        {
            qWarning()<<"Database not initialized or cannot be opened ";
        }
    }
    return db;
}

bool sqliteDB::initDB()
{
    QDir db_dir;
    if(!db_dir.exists(m_sDBPath))
    {
        bool success = db_dir.mkpath(m_sDBPath);
        if(success)
        {
            qDebug()<<"创建路径成功!";
        }else
        {
            qWarning()<<"创建路径失败！";
            return false;
        }
    }
    QString dir = m_sDBPath+"/"+m_sDBName;

    qDebug() << dir;

    //db = QSqlDatabase::addDatabase("QSQLITE");
    db.setDatabaseName(dir);
    if(!db.open())
    {
        qWarning()<<"数据库打开失败";
        return false;
    }
        qDebug() << "__________XXXXX";
    // 创建表（如果尚未存在）
    if ( !createSettingConfigTable()) {
        return false;
    }

    return true;
}

//创建设置配置表，只需要主机的IP
bool sqliteDB::createSettingConfigTable()
{
    QMutexLocker locker(&mutex);
    if(!db.isOpen())
    {
        return false;
    }
    bool createRet = false;
    if(db.tables().contains("OvenIPTable"))
    {
        createRet = true;
    }
    else
    {
        QSqlQuery query(db);
        QString str_createSql = QString("create table if not exists OvenIPTable ( \
                                        Id INTEGER PRIMARY KEY AUTOINCREMENT,\
                                        OvenIP TEXT NOT NULL)");
            createRet = query.exec(str_createSql);
        if(!createRet)
        {
            qWarning()<<"创建IP配置表失败!"<<query.lastError().text();
        }
        else
        {
            //第一次创建，默认存储主机连接的IP
            QString str_insertSql = QString("insert into OvenIPTable values(1,'192.168.155.200')");
            if(!query.exec(str_insertSql))
            {
                qWarning()<<"Insert default setting Error="<<query.lastError().text();
            }
        }
    }
    return createRet;
}

//获取设置配置
QString sqliteDB::getOvenIPAddress()
{
    QMutexLocker locker(&mutex);

    QString IPAddress;//返回的主机IP地址
    if(!db.isOpen())
    {
        return "";
    }
    QSqlQuery query(db);
    QString str_selectSql = QString("select OvenIP from OvenIPTable where Id = 1;");
    if(query.exec(str_selectSql))
    {
        while (query.next())
        {
            IPAddress = query.value(0).toString()  ;
        }

    }
    return IPAddress;
}

//更新表主机IP
bool sqliteDB::updateOvenIPAddress(QString IPAddress)
{
    QMutexLocker locker(&mutex);
    if(!db.isOpen())
    {
        return false;
    }

    QSqlQuery query(db);
    QString str_selectSql = QString("REPLACE INTO OvenIPTable(Id,OvenIP) VALUES(1,'%1');").arg(IPAddress);
    if(!query.exec(str_selectSql))
    {
        qWarning()<<"update ip_config error"<<query.lastError().text();
        emit sig_logInfo("保存IP设置失败！");
        return false;
    }
    return true;
}