nsITraceableChannel 确实是这里的路。 Jan Odvarko (softwareishard.com) 和我自己 (ashita.org) 的博客文章展示了如何做到这一点。您可能还想查看http://www.ashita.org/implementing-an-xpcom-firefox-interface-and-creating-observers/，但实际上并不需要在 XPCOM 组件中执行此操作。
步骤基本上是：
- 创建实现 nsITraceableChannel 的对象原型；并创建观察者来监听 http-on-modify-request 和 http-on-examine-response
- 注册观察者
- 监听这两种请求类型的观察者将我们的 nsITraceableChannel 对象添加到监听器链中，并确保我们的 nsITC 知道谁是链中的下一个
- nsITC 对象提供三个回调，每个回调都会在适当的阶段被调用：onStartRequest、onDataAvailable 和 onStopRequest
- 在上述每个回调中，我们的 nsITC 对象必须将数据传递给链中的下一项
以下是我编写的特定于站点的插件的实际代码，据我所知，它的行为与您的非常相似。
function TracingListener() {
//this.receivedData = [];
}
TracingListener.prototype =
{
originalListener: null,
receivedData: null, // array for incoming data.
onDataAvailable: function(request, context, inputStream, offset, count)
{
var binaryInputStream = CCIN("@mozilla.org/binaryinputstream;1", "nsIBinaryInputStream");
var storageStream = CCIN("@mozilla.org/storagestream;1", "nsIStorageStream");
binaryInputStream.setInputStream(inputStream);
storageStream.init(8192, count, null);
var binaryOutputStream = CCIN("@mozilla.org/binaryoutputstream;1",
"nsIBinaryOutputStream");
binaryOutputStream.setOutputStream(storageStream.getOutputStream(0));
// Copy received data as they come.
var data = binaryInputStream.readBytes(count);
//var data = inputStream.readBytes(count);
this.receivedData.push(data);
binaryOutputStream.writeBytes(data, count);
this.originalListener.onDataAvailable(request, context,storageStream.newInputStream(0), offset, count);
},
onStartRequest: function(request, context) {
this.receivedData = [];
this.originalListener.onStartRequest(request, context);
},
onStopRequest: function(request, context, statusCode)
{
try
{
request.QueryInterface(Ci.nsIHttpChannel);
if (request.originalURI && piratequesting.baseURL == request.originalURI.prePath && request.originalURI.path.indexOf("/index.php?ajax=") == 0)
{
var data = null;
if (request.requestMethod.toLowerCase() == "post")
{
var postText = this.readPostTextFromRequest(request, context);
if (postText)
data = ((String)(postText)).parseQuery();
}
var date = Date.parse(request.getResponseHeader("Date"));
var responseSource = this.receivedData.join('');
//fix leading spaces bug
responseSource = responseSource.replace(/^\s+(\S[\s\S]+)/, "$1");
piratequesting.ProcessRawResponse(request.originalURI.spec, responseSource, date, data);
}
}
catch (e)
{
dumpError(e);
}
this.originalListener.onStopRequest(request, context, statusCode);
},
QueryInterface: function (aIID) {
if (aIID.equals(Ci.nsIStreamListener) ||
aIID.equals(Ci.nsISupports)) {
return this;
}
throw Components.results.NS_NOINTERFACE;
},
readPostTextFromRequest : function(request, context) {
try
{
var is = request.QueryInterface(Ci.nsIUploadChannel).uploadStream;
if (is)
{
var ss = is.QueryInterface(Ci.nsISeekableStream);
var prevOffset;
if (ss)
{
prevOffset = ss.tell();
ss.seek(Ci.nsISeekableStream.NS_SEEK_SET, 0);
}
// Read data from the stream..
var charset = "UTF-8";
var text = this.readFromStream(is, charset, true);
// Seek locks the file so, seek to the beginning only if necko hasn't read it yet,
// since necko doesn't seek to 0 before reading (at lest not till 459384 is fixed).
if (ss && prevOffset == 0)
ss.seek(Ci.nsISeekableStream.NS_SEEK_SET, 0);
return text;
}
else {
dump("Failed to Query Interface for upload stream.\n");
}
}
catch(exc)
{
dumpError(exc);
}
return null;
},
readFromStream : function(stream, charset, noClose) {
var sis = CCSV("@mozilla.org/binaryinputstream;1", "nsIBinaryInputStream");
sis.setInputStream(stream);
var segments = [];
for (var count = stream.available(); count; count = stream.available())
segments.push(sis.readBytes(count));
if (!noClose)
sis.close();
var text = segments.join("");
return text;
}
}
hRO = {
observe: function(request, aTopic, aData){
try {
if (typeof Cc == "undefined") {
var Cc = Components.classes;
}
if (typeof Ci == "undefined") {
var Ci = Components.interfaces;
}
if (aTopic == "http-on-examine-response") {
request.QueryInterface(Ci.nsIHttpChannel);
if (request.originalURI && piratequesting.baseURL == request.originalURI.prePath && request.originalURI.path.indexOf("/index.php?ajax=") == 0) {
var newListener = new TracingListener();
request.QueryInterface(Ci.nsITraceableChannel);
newListener.originalListener = request.setNewListener(newListener);
}
}
} catch (e) {
dump("\nhRO error: \n\tMessage: " + e.message + "\n\tFile: " + e.fileName + " line: " + e.lineNumber + "\n");
}
},
QueryInterface: function(aIID){
if (typeof Cc == "undefined") {
var Cc = Components.classes;
}
if (typeof Ci == "undefined") {
var Ci = Components.interfaces;
}
if (aIID.equals(Ci.nsIObserver) ||
aIID.equals(Ci.nsISupports)) {
return this;
}
throw Components.results.NS_NOINTERFACE;
},
};
var observerService = Cc["@mozilla.org/observer-service;1"]
.getService(Ci.nsIObserverService);
observerService.addObserver(hRO,
"http-on-examine-response", false);
在上面的代码中，originalListener 是我们之前在链中插入的监听器。在创建跟踪侦听器时保留该信息并在所有三个回调中传递数据是至关重要的。否则什么都不会起作用（页面甚至不会加载。Firefox 本身是链中的最后一个）。
注意：上面的代码中调用了一些函数，它们是 piratequesting 插件的一部分，例如：parseQuery() 和 dumpError()