nsITraceableChannel

使用这个接口的典型方式如下：

• 注册“http-on-examine-response”通知来跟综全部 HTTP 响应；
• 跳过重定义 (responseStatus = 3xx on nsIHttpChannel)，否则你可能最终有两个监听视（listeners）注册通道（channel）;
• QI the channel passed as the "subject" to your observer to nsITraceableChannel, and replace the default nsIStreamListener (that passes the data to the original requester - e.g. to XMLHttpRequest or to the browser tab that made the request) with your own implementation (see "Implementing nsIStreamListener" below).

之后，你的 nsIStreamListener 实现将会获取到响应数据（response data），并且能够传递数据到原始的 nsIStreamListener（可能会修改它）。

See nsITraceableChannel, Intercept HTTP Traffic for a more detailed description with code samples.

See Modify URL before loading page in firefox for an overview of how to modify a request before it is made.

Method overview

Methods

setNewListener()

用一个新的来替换该通道的当前监听器，返回先前分配给该通道的监听器。

nsIStreamListener setNewListener(
  in nsIStreamListener aListener
);

参数

aListener

An nsIStreamListener to be notified of events on the HTTP channel.

返回值

该通道的前一个监听器。Each listener call through to the previous listener for every call, in order to establish a call chain to allow all interested parties a chance to act on each event.

实现 nsIStreamListener

一个 nsIStreamListener 接口传递给 setNewListener() 需要实现下列的方法，这是通过调用（这些方法）来通知它在 HTTP stream 上发生的事件：

• onStartRequest：一个 HTTP 请求开始。
• onDataAvailable：数据到达 HTTP 通道（HTTP channel）。
• onStopRequest：HTTP 请求结束。

Channels may restrict when you may replace the listener. In particular, listeners typically should not be replaced after onStartRequest has been called.