在检查响应时在http之前返回响应

Question

我正在开发一个Firefox插件，它需要拦截HTTP请求过程，并为某些URL返回虚假响应。这是我正在使用的代码：

function TracingListener() {
    this.originalListener = null;
}
TracingListener.prototype = {
    onDataAvailable: function(request, context, inputStream, offset, count) {
        LOG("onDataAvailable");
        this.originalListener.onDataAvailable(request, context, inputStream, offset, count);
    },
    onStartRequest: function(request, context) {
        LOG("onStartRequest");
        this.originalListener.onStartRequest(request, context);
    },

    onStopRequest: function(request, context, statusCode) {
        LOG("onStopRequest");
        this.originalListener.onStopRequest(request, context, statusCode);
        var stream = Cc["@mozilla.org/io/string-input-stream;1"].createInstance(Ci.nsIStringInputStream);
        stream.setData("Test", -1);
        this.originalListener.onStopRequest(request, context, Components.results.NS_OK);
    },
    QueryInterface: function (aIID) {
        if (aIID.equals(Ci.nsIStreamListener) ||
        aIID.equals(Ci.nsISupports)) {
            return this;
        }
        throw Components.results.NS_NOINTERFACE;
    }
};
var observer = {
    observe: function(subject, topic, data) {
        LOG(topic);
        var httpChannel = subject.QueryInterface(Ci.nsIHttpChannel);
        var url = httpChannel.URI.spec;
        LOG("Test:" + url);
        if (!pattern.test(url)) return;
        if (topic == 'http-on-modify-request') {
            var newListener = new TracingListener();
            newListener.originalListener = httpChannel.setNewListener(newListener);
            } else if (topic == "http-on-examine-response" || topic == "http-on-examine-cached-response" || topic == "http-on-examine-merged-response") {
            var newListener = new TracingListener();
            newListener.originalListener = httpChannel.setNewListener(newListener);
        }
    }
};

var observerService = Cc["@mozilla.org/observer-service;1"].getService(Ci.nsIObserverService);
observerService.addObserver(observer, "http-on-modify-request", false);
observerService.addObserver(observer, "http-on-opening-request", false);

当有URL响应时，它工作得很好：我可以将响应更改为"Test"。

但是，对于一些无法访问或速度非常慢的URL，永远不会调用onStopRequest。

在发送任何真正的请求之前，我需要返回一个请求，即"打开请求时的http"或"修改请求时的http"。但在这一点上，Firefox拒绝接受任何响应，因为他认为（这是真的）该响应不应该可用。

我该怎么做？

Answer 1

在http-on-modify-request上，您应该能够调用redirectTo或修改nsIChannel.URI以将请求发送到类似data:text/plain,Test的数据URI。