I'm writing a extension which has to make a HTTP request to a web
service. While I figured out how to make async requests, I'm stuck
with making snychronous calls.Let me first outline what I'm currently
doing and then ask my questions.
Here are the steps for establishing a httpConnection involved as I
see it :
* Convert String to an URI
* Convert URI to a channel
* QI the channel into a HTTPChannel using the nsIHttpChannel
* Creat an inputStream through the nsIStringInputStream interface
* Set the uplad stream of the http channel to be this new input stream
* Create a stream listener for the channel
- Implement the onStartRequest, onDataAvailable , onStopRequest ,
onChannelRedirect ,getInterface , onProgress , onStatus , onRedirect
and QueryInterface
- Specify a callback function for this listener
* open channel using the 'asyncOpen' function call.
While the above steps work fine for making asynchronous http
requests , I'm stuck with figuring out how to make synchronous
requests. I gather it isn't as simple as replacing the asncOpen
function call with a 'open' function call.
I'm providing my code below , if it helps. Thanks for your help. I'm a
noob at JS programming so please don't cuss me if my code sucks :D
(would appreciate knowing why it sucks though).
/*
What I want to do is, when the initialise function is called, I want
the result of the http request to be stored in the returnString
variable rather than be sent to the CallBack function
*/
function initialise()
{
var aData = 'sampleData';
var aMethod = "Post" ;
var aContextType = "application/x-www-form-urlencoded" ;
var hc = new HttpConnection('http://localhost:8080/cgi-bin/
hello.cgi');
var returnString = hc.sendData(aData,aMethod,aContextType);
}
function HttpConnection(aUrlString)
{
this.url = aUrlString ;
var uri = _stringToUri(aUrlString) ;
this.channel = _uriToChannel(uri) ;
}
HttpConnection.prototype.getUrlString = function()
{
return this.url ;
}
HttpConnection.prototype.sendData = function(aData,aMethod,
aContextType)
{
var httpChannel = _makeHttpChannel(this.channel);
var inputStream = Components.classes["@mozilla.org/io/string-input-
stream;1"]
.createInstance(Components.interfaces.nsIStringInputStream);
inputStream.setData(aData,-1);
httpChannel.requestMethod = aMethod;
httpChannel.setUploadStream(inputStream,aContextType, -1);
httpChannel.requestMethod = aMethod;
var listener = new StreamListener(callBack);
httpChannel.asyncOpen(listener, null);
}
function _stringToUri(aUrlString)
{
var ioService = Components.classes["@mozilla.org/network/io-service;
1"]
.getService(Components.interfaces.nsIIOService);
var uri = ioService.newURI(aUrlString, null, null);
return uri ;
}
function _uriToChannel(aUri)
{
var ioService = Components.classes["@mozilla.org/network/io-service;
1"]
.getService(Components.interfaces.nsIIOService);
var channel = ioService.newChannelFromURI(aUri);
return channel ;
}
function _makeHttpChannel(aChannel)
{
var uploadChannel =
aChannel.QueryInterface(Components.interfaces.nsIUploadChannel);
var httpChannel =
uploadChannel.QueryInterface(Components.interfaces.nsIHttpChannel);
return httpChannel ;
}
function StreamListener(aCallbackFunc) {
this.mCallbackFunc = aCallbackFunc;
}
StreamListener.prototype = {
mData: "",
onStartRequest: function (aRequest, aContext) {
this.mData = "";
},
onDataAvailable: function (aRequest, aContext, aStream,
aSourceOffset, aLength) {
var scriptableInputStream = Components.classes["@mozilla.org/
scriptableinputstream;
1"].createInstance(Components.interfaces.nsIScriptableInputStream);
scriptableInputStream.init(aStream);
this.mData += scriptableInputStream.read(aLength);
},
onStopRequest: function (aRequest, aContext, aStatus) {
if (Components.isSuccessCode(aStatus)) {
this.mCallbackFunc(this.mData);
} else {
this.mCallbackFunc(null);
}
httpChannel = null;
},
onChannelRedirect: function (aOldChannel, aNewChannel, aFlags) {
httpChannel = aNewChannel;
},
// nsIInterfaceRequestor
getInterface: function (aIID) {
try {
return this.QueryInterface(aIID);
} catch (e) {
throw Components.results.NS_NOINTERFACE;
}
},
onProgress : function (aRequest, aContext, aProgress, aProgressMax)
{ },
onStatus : function (aRequest, aContext, aStatus, aStatusArg) { },
onRedirect : function (aOldChannel, aNewChannel) { },
QueryInterface : function(aIID) {
if (aIID.equals(Components.interfaces.nsISupports) ||
aIID.equals(Components.interfaces.nsIInterfaceRequestor) ||
aIID.equals(Components.interfaces.nsIChannelEventSink) ||
aIID.equals(Components.interfaces.nsIProgressEventSink) ||
aIID.equals(Components.interfaces.nsIHttpEventSink) ||
aIID.equals(Components.interfaces.nsIStreamListener))
return this;
throw Components.results.NS_NOINTERFACE;
}
};
function callBack(x)
{
alert(x);
}
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