Hi!
I'm trying to develop a Firefox (v2.0.0.6) extension, which should check
(and perhaps modify) the contents of a site having been retrieved,
before it is shown by firefox.
Up to now, I have registered an observer to the http-on-examine-response
event. The observer receives an HttpChannel as subject. I would like to
call subject.asyncOpen but I get an error that the method is unknown.
Error: Component returned failure code: 0x804b000f [nsIChannel.open] =
<unknown>
So, I copy the URI of the channel and have the IOservice create a new
channel. Before that, I have to remove the observer to prevent an
infinite loop since the creating a new channel will emit a new event.
Now I can call asyncOpen with a streamListener and read data from the
input stream. After modifying data, I could write them to disk and open
the file:// url in a new tab, but it would be better if the browser
showed the modified site automatically.
My main question is: How can I modify the data, so the modified web site
is displayed in the browser?
Another question is why I cannot use subject.asyncOpen. Instead I have
to open a new channel to the URI's address, and then call asyncOpen().
Best Regards and thanks in advance,
Steffen
P.S.: Up to now my implementation looks like this:
function Observer() {}
Observer.prototype = {
observe: function(subject,topic,data){
subject.QueryInterface(Components.interfaces.nsIChannel);
observerService.removeObserver(this,"http-on-examine-response");
dump(subject.URI.spec);
var ioService =
Components.classes["@mozilla.org/network/io-service;1"].getService(Components.interfaces.nsIIOService);
var scriptableStream =
Components.classes["@mozilla.org/scriptableinputstream;1"].getService(Components.interfaces.nsIScriptableInputStream);
var channel = ioService.newChannel(subject.URI.spec,null,null);
channel.asyncOpen(streamListener, null);
// observerService.addObserver(this, "http-on-examine-response", false);
dump("opened channel"+"\n");
},
QueryInterface: function(iid) {
if (!iid.equals(Components.interfaces.nsIObserver))
throw Components.results.NS_ERROR_NO_INTERFACE;
dump("object of type nsIObserver");
return this;
}
}
var streamListener = {
data: "",
onDataAvailable: function( /*nsIRequest*/ request , /*nsISupports*/
context, /*nsIInputStream*/ inputStream , /*PRUint32*/ offset ,
/*PRUint32*/ count) {
var scriptableInputStream =
Components.classes["@mozilla.org/scriptableinputstream;1"].createInstance(Components.interfaces.nsIScriptableInputStream);
scriptableInputStream.init(inputStream);
this.data += scriptableInputStream.read(count);
dump("OnDataAvailable:"+ this.data);
this.data = this.data.replace("Erweiterte","Buh");
this.data = this.data.replace("Auf","Buh2");
dump("OnDataAvailable:"+ this.data);
},
onStartRequest: function(request, context){ dump("stepped into
onStartRequest" + "\n");},
onStopRequest: function(request, context, status)
{
if (Components.isSuccessCode(status))
{
dump("success\n");
}
var wm =
Components.classes["@mozilla.org/appshell/window-mediator;1"].getService(Components.interfaces.nsIWindowMediator);
var browserWindow = wm.getMostRecentWindow("navigator:browser");
// browserWindow.QueryInterface(Components.interfaces.nsIDOMJSWindow);
var browser = browserWindow.getBrowser();
browser.addTab("file:///E:/temp/test2.htm", null, null, null, null,
null);
//browser.removeCurrentTab();
},
QueryInterface: function(iid) {
if (!iid.equals(Components.interfaces.nsIStreamListener))
throw Components.results.NS_ERROR_NO_INTERFACE;
dump("object of type nsIStreamListener");
return this;
}
};
// initialization
function NSGetModule() {
observerService.addObserver(new Observer(),
http-on-examine-response", false);
dump("register observer\n");
dump("loaded grid services browser add-on\n");
return browserModule;
}
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