在 URLConnection 中设置标头的正确方法是什么?

我的代码如下:

URLConnection cnx = address.openConnection();
cnx.setAllowUserInteraction(false);         
cnx.setDoOutput(true);
cnx.addRequestProperty("User-Agent", 
    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)");
InputStream is = cnx.getInputStream();

如果我在获得 InputStream 之前设置标头可以吗?我的标头会被发送，还是服务器会看到默认的 URLConnection 的用户代理(如果有)?

Is it ok if I set the headers before I get the InputStream? Will my header be sent, or will the server see the default URLConnection's user-agent ( if any ) ?

推荐答案

在获得 InputStream 之前必须设置标头 以产生任何影响 - 如果连接已经打开，将抛出 IllegalStateException.

The headers must be set prior to getting the InputStream to have any affect - an IllegalStateException will be thrown if the connection is already open.

具体到 User-Agent 标头，如果已设置则应发送.

As far as the User-Agent header specifically, it should be sent if it has been set.

请参阅 URLConnection JavaDoc.

See the URLConnection JavaDoc.