Re: Cannot call RegisterDataSource on a own datasource

On 4 fév, 14:52, Axel Hecht <[email protected]> wrote:
> mcben wrote:
> > On 4 fév, 09:27, Axel Hecht <[email protected]> wrote:
> >> mcben wrote:
> >>> Hi folks,
> >>> Here is quite a long post about a problem with a own datasource
> >>> implementation based on a xml-datasource.
> >>> I'm looking for any clues or links that could help me to achieve my
> >>> first goal : a custom datasource that i could fill from a CSV file.
> >>> Thanks in advance for reading me :)
> >>> I'm creating a javascript component that fetches a CSV file with
> >>> XMLHttpRequest, parses it, then adds lines as RDF resources in a RDF
> >>> datasource.
> >>> Its contractid is like "@mozilla.org/rdf/datasource;1?name=mydatasource"
> >>> so as to get it in the chrome with the "rdf:mydatasource" keyword.
> >>> I started this work by using an in-memory-datasource as the __proto__
> >>> properties of my javascript prototype.
> >>> I could fetch my file and appends data in the datasource : the result
> >>> was shown in a rdf tree.
> >>> The first problem with this design was that i was not able to overwrite
> >>> some nsIRDFDataSource methods (not a real problem in fact), nor extends
> >>> the in-memory-datasource component with other interfaces : the QI method
> >>> of my component was never called, so i got a NS_ERROR_NO_INTERFACE
> >>> error, when i QI another interface (eg: nsIDOMListener to adds
> >>> XMLHttpRequest callback in my chrome).
> >>> Then i took a look a the rdf:localstore C++ implementation
> >>> (nsLocalStore.cpp) and i'm quite happy with its design : it works like a
> >>> wrapper around a xml-datasource. It "justs" load data from
> >>> localstore.rdf in the profile directory or creates it if it does not exist.
> >>> Then with that, I could even read and store a cached version of my CSV
> >>> file on disk.
> >>> So, I've made the same design in my javascript component, all
> >>> nsIRDFDataSource related methods are forwarded to a "mInner"
> >>> xml-datasource property.
> >>> But when i try to call RegisterDataSource to register my datasource in
> >>> the constructor of my component, it throws a NS_ERROR_FAILURE :
> >>> Here is the code :
> >>> this._loadLocalData();
> >>> RDF.RegisterDataSource(this, false);
> >>> this._loadRemoteData();
> >>> If i log "this" the console service returns me that is an Object.
> >>> That's the problem ?
> >>> In fact I get from the chrome : [xpconnect wrapped (nsISupports,
> >>> nsIRDFDataSource, nsIRDFRemoteDataSource)] after the registration, even
> >>> if the registration fails.
> >>> But, the nsIRDFRemoteDatasource Init method is called at every calls
> >>> from chrome.
> >>> Maybe the real problem comes from the xml-datasource initialization.
> >>> The following code is called by the constructor of my component :
> >>> this.mInner = Components
> >>>        .classes["@mozilla.org/rdf/datasource;1?name=xml-datasource"]
> >>>        .createInstance(Components.interfaces.nsIRDFDataSource);
> >>> var remote = this.mInner
> >>>        .QueryInterface(Components.interfaces.nsIRDFRemoteDataSource);
> >>> remote.Init(filespec);
> >>> The "Init" call throws an exception with the following code
> >>> "0x804b000a". Its related with nsISocketTransport and means
> >>> STATUS_WAITING_FOR. Ok, why not.
> >>> Then remote.loaded returns false, and calling remote.Refresh(false)
> >>> throws a NS_ERROR_FAILURE
> >>> What is wrong with that ?
> >>> So i catch this Init exception and get my remote datasource with the RDF
> >>> Service like this :
> >>> remote = RDF.GetDataSource(filespec)
> >>>           .QueryInterface(Components.interfaces.nsIRDFRemoteDataSource)
> >>> this.mInner = remote
> >>>           .QueryInterface(Components.interfaces.nsIRDFDataSource);
> >>> In that case no problem with remote ds, but the RegisterDataSource go on
> >>> failing.
> >>> And later, in the chrome, when i call a method or property that is
> >>> forwarded to the inner, i got back a undefined result.
> >>> And i cant look any result in my xul tree.
> >>> I can post the full source code of the component if needed.
> >> I suspect that it has something to do with your move from an in-memory
> >> datasource as inner to an rdf/xml as inner. I didn't get why you made
> >> that move, was that intentional?
>
> > Hi Axel,
> > Thank you for your answer.
>
> > To begin, you can grab my component source code here, with the "second
> > design" implementation (with inner):
> >http://pastebin.mozilla.org/319272
>
> > And the xul tree that should show my results look quite simple :
> > <tree id="itemtypes-tree" flex="1"
> >         datasources="rdf:bi-itemtypes" ref="bi:itemtypes-list">
> >   <treecols>
> >     <treecol id="col-name" primary="true" label="Name" flex="1"/>
> >   </treecols>
> >   <template>
> >     <treechildren>
> >       <treeitem uri="rdf:*">
> >         <treerow>
> >           <treecell label="rdf:*" />
> >         </treerow>
> >       </treeitem>
> >     </treechildren>
> >   </template>
> > </tree>
>
> > Hum. yes, the move was partially intentional :
>
> >  * My first try with an in-memory datasource was with the instance set
> > as __proto__ property in the prototype of my component. That is to
> > say, that it was not with the "inner" design.
> > The main problem with this design was that i could not extends my
> > component by implementing other public interface : the QI function of
> > my component was never called, nor any method that i though they
> > overrode existing methods of the in-mem. The only thing that i could
> > improve in this design was the init phase of my component (by filling
> > in-mem with XMLHttpRequest) nothing else.
>
> > Is it normal that with the following code, the QueryInterface method
> > is never called, that's why i cant implement any other interfaces ? (i
> > think that the __proto__ QI is called instead).
>
> > function myComponentImplementation() {
> > }
> > myComponentImplementation.prototype {
> >     __proto__ : Components.classes["@mozilla.org/rdf/datasource;1?
> > name=in-memory-datasource"]
> >                          .createInstance(Components.interfaces.nsIRDFDataSource),
>
> >     QueryInterface : function(iid) {
> >         if (!iid.equals(C_i.nsIDOMEventListener) &&
> >             !iid.equals(C_i.nsIRDFDataSource) &&
> >             !iid.equals(C_i.nsIRDFRemoteDataSource) &&
> >             !iid.equals(C_i.nsISupports))
> >             throw Components.results.NS_ERROR_NO_INTERFACE;
> >         ConsoleService.logStringMessage("QI called:" + iid);
> >         return this;
> >     }
> > }
>
> >  * With the "inner" design, i immediatly use a xml-datasource, just
> > like the nsLocalStore implementation. With that, i could load a cached
> > version of the rdf file from disk, and then update it with
> > XMLHttpRequest only if it really needed.
>
> > Since, you are thinking that the problem can come from the xml-
> > datasource, i took the same component, and just replaced the xml-
> > datasource inner, with an in-memory-datasource.
> > Indeed, it seems there is no major failure with initialization, i can
> > register the datasource, but the content that i downloaded with
> > XMLHttpRequest and that i put in the ds is not reflected in my chrome
> > xul tree, nor i can query my datasource for any target that sould
> > exists.
>
> > More precisely, about any errors, i had to create the container (the
> > one to wich I append downloaded resources) with this.mInner (the in-
> > mem ds) and not my component. Is it normal ?
> > Look:
> > this._container = RDFContainer.MakeSeq(this.mInner,
> > RDF.GetResource(this._struct.ref));
> > Even though my component should implement nsIRDFDataSource, that's why
> > i thought i could do that :
> > this._container = RDFContainer.MakeSeq(this,
> > RDF.GetResource(this._struct.ref));
>
> > But it seems that append does not work anyway.
>
> > * Finally, why I made the move to xml-datasource ?
> > (I thought) I could parse a local rdf file at init, and flushes the
> > modified results at destruction. I even could observe the download
> > progress from chrome (eg: with a progressbar), etc.
>
> > So any clue ?
> > What do you think is the best implementation ?
>
> > The first design could be perfect if i could override and extends
> > methods and interfaces of the __proto__ instance.
>
> > Thank you for reading me.
>
> I suspect that something in your implementation is broken. There ishttp://developer.mozilla.org/en/docs/Aggregating_the_In-Memory_Dataso...,
> but that hasn't been maintained in years, same goes for its sibling
> documents.

Yes, i know this document, and tried some months ago to agregate a xml-
datasource (for another project) and gave up when i saw that xml-
datasource cant be aggregated ;-)

Maybe i should give another try with the in-mem datasource.

But can you confirm me that i could try that with a javascript
implementation ?


> Sorry, no better idea, maybe if you post parts of your code there's
> better chances.

Héhé. The whole component is too long / time consuming for you to take
a look ?
I understand.

So first question, that i previously asked. WIth a component
implementation below, is it normal that I cant override public methods
of the __proto__. In fact, I can only add private method, that cant be
accessed by the chrome ?

function myComponentImplementation() {
}

myComponentImplementation.prototype {
    __proto__ : Components.classes["@mozilla.org/rdf/datasource;1?
name=in-memory-datasource"]
                         .createInstance(Components.interfaces.nsIRDFDataSource),

    QueryInterface : function(iid) {
        if (!iid.equals(C_i.nsIDOMEventListener) &&
            !iid.equals(C_i.nsIRDFDataSource) &&
            !iid.equals(C_i.nsIRDFRemoteDataSource) &&
            !iid.equals(C_i.nsISupports))
            throw Components.results.NS_ERROR_NO_INTERFACE;
        ConsoleService.logStringMessage("QI called:" + iid);
        return this;
    }

}