[Qt-qml] NetworkAccessManager

[Martin Jones]

On Wed, 28 Apr 2010 11:12:11 pm ext Jack Wootton wrote:
> To follow up on this.  I have been reading the documentation for
> QNetworkProxyFactory:
> http://doc.qt.nokia.com/4.7-snapshot/qnetworkproxyfactory.html
> 
> For the method
> 
> QList<QNetworkProxy> QNetworkProxyFactory::systemProxyForQuery ( const
> QNetworkProxyQuery & query = QNetworkProxyQuery() )   [static]
> 
> it is documented that: "On Windows, this function will use the WinHTTP DLL
> functions. Despite its name, Microsoft suggests using it for all
> applications that require network connections, not just HTTP. This will
> respect the proxy settings set on the registry with the proxycfg.exe tool.
> If those settings are not found, this function will attempt to obtain
> Internet Explorer's settings and use them."
> 
> I'm have set my proxy using proxycfg tool on Windows, however I still get
> no proxy results from QNetworkProxyFactory::systemProxyForQuery

QNetworkProxyFactory::systemProxyForQuery() requires a QNetworkProxyQuery to 
be passed to it.  This would also require using a QNetworkProxyFactory, rather 
than simply setting a proxy for the QNetworkAccessManager.  If you want to do 
this then you can see the qml runtime source for inspiration - 
tools/qml/qmlruntime.cpp (search for SystemProxyFactory).

To begin, I think you should get the code below working, though.  I suspect 
the reason it does not work is that you have not provided a valid host name:

     proxy.setHostName("my.proxy.com<http://my.proxy.com>");

changing it to this should make it work:

     proxy.setHostName("my.proxy.com");

assuming my.proxy.com is a valid proxy.

I've added a simple example to examples/declarative/proxyviewer, illustrating 
how to use a QDeclarativeNetworkAccessManagerFactory (should appear on 
gitorious within 24hrs).  The code is essentially the same as you have below, 
so with a correct proxy set this should work.

Martin.

> On Tue, Apr 27, 2010 at 2:35 PM, Jack Wootton
> <jackwootton at gmail.com<mailto:jackwootton at gmail.com>> wrote: Hello,
> 
> I have modifed the my implementation of
> QDeclarativeNetworkAccessManagerFactory (question follows code) :)
> 
> MyNetworkAccessManagerFactory.h
> ===========================
> class MyNetworkAccessManagerFactory : public
> QDeclarativeNetworkAccessManagerFactory {
> public:
>      MyNetworkAccessManagerFactory();
>      ~MyNetworkAccessManagerFactory();
> 
> public:
>     QNetworkAccessManager* create ( QObject * parent );
> };
> 
> 
> MyNetworkAccessManagerFactory.cpp
> =============================
> MyNetworkAccessManagerFactory::MyNetworkAccessManagerFactory()
> {
> }
> 
> MyNetworkAccessManagerFactory::~MyNetworkAccessManagerFactory()
> 
> {
> }
> 
> QNetworkAccessManager* MyNetworkAccessManagerFactory::create ( QObject*
> parent ) {
>      QNetworkProxy proxy;
>      proxy.setHostName("my.proxy.com<http://my.proxy.com>");
> 
>      proxy.setPort(3128);
> 
>      // Is this static method call acceptable for a re-entrant method?
>      // QNetworkProxy::setApplicationProxy(proxy);
> 
>      QNetworkAccessManager* nam = new QNetworkAccessManager(parent);
> 
> 
>      nam->setProxy(proxy);
>      return nam;
> }
> 
> 
> 
> I have a question about ensuring the method create(QObject* parent) is
> thread safe / re-entrant: I assumed the method call
> 'QNetworkProxy::setApplicationProxy(proxy);' is not ok since it is static
> and should not be called from a re-entrant function.  Is this the case? 
> If so, is it a problem that it is not called?
> 
> I made the changes, but I still don't see the webpage loaded in the QML
> document, but I'll deal with that after I know my code is correct first :)
> 
> 
> 
> On Tue, Apr 27, 2010 at 2:19 AM, Martin Jones
> <martin.jones at nokia.com<mailto:martin.jones at nokia.com>> wrote:
> 
> On Tue, 27 Apr 2010 01:18:56 am ext Jack Wootton wrote:
> > Hi,
> > 
> > I'm trying to set some proxy settings for a QML application - it's not
> > working as expected.  I'm unsure the API is being used correctly, can
> > someone check my code makes sense? There are 3 files: main.cpp,
> > MyNetworkAccessManagerFactory.h and MyNetworkAccessManagerFactory.cpp
> > 
> > I'm using qt 4.7 and followed the documentation
> > (http://doc.qt.nokia.com/4.7-snapshot/qdeclarativenetworkaccessmanagerfac
> > t ory.html) when writing the code.  The method
> > MyNetworkAccessManagerFactory::create(QObject* parent) does get called
> > when the QML document is loaded using the QDeclarativeView, so the
> > framework is definitely picking up the new proxy settings.
> > 
> > The questions I have are:
> > 
> > 1. Is the implementation of MyNetworkAccessManagerFactory::create
> > correct? I assumed because I was subclassing from a class with 'factory'
> > in its name, that it was ok to return the same pointer to
> > NetworkAccessManager.
> > 
> > 2. How do I know if the method that calls "create" takes ownership of the
> > returned pointer or not?  I assumed it didn't, hence cleaning up in
> > ~MyNetworkAccessManagerFactory();
> > 
> > 3. Is there anything obviously wrong with the way I'm using the
> > NetworkAccessManager?
> 
> The factory must create a  new NAM each time it is called.  This is because
> QML creates multiple threads and each must have its own NAM.  It is
> important that you set the parent of the NAM created to the parent passed
> in the create() method (which you already do).  The NAM will be destroyed
> when its parent is destroyed.  I will update the documentation to make
> this clear.
> 
> Also take special note of this line from the documentation:
> 
> "Note: the create() method may be called by multiple threads, so ensure the
> implementation of this method is reentrant."
> 
> --
> Martin
> 
> 
> 
> --
> Regards
> Jack
> 
> 
> 
> --
> Regards
> Jack

-- 
Martin