class ArxTemplate : public AcRxArxApp
{
    inline static bool isInitialized = false;
public:
    ArxTemplate() : AcRxArxApp()
    {
    }

    virtual AcRx::AppRetCode On_kInitAppMsg(void* pkt)
    {
        AcRx::AppRetCode retCode = AcRxArxApp::On_kInitAppMsg(pkt);
        //init app context 
        return (retCode);
    }

    virtual AcRx::AppRetCode On_kUnloadAppMsg(void* pkt)
    {
        AcRx::AppRetCode retCode = AcRxArxApp::On_kUnloadAppMsg(pkt);
        return (retCode);
    }

    virtual AcRx::AppRetCode On_kLoadDwgMsg(void* pkt) override
    {
        AcRx::AppRetCode retCode = AcRxDbxApp::On_kLoadDwgMsg(pkt);
        initOnce();
        return retCode;
    }

    virtual void RegisterServerComponents()
    {
    }

    bool initOnce()
    {
        if (!isInitialized)
        {
            isInitialized = true;
            //init document context
        }
        return isInitialized;
    }
...
};