如何在Java中获得无代理连接？

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在与 URLConnection 建立连接时，如何避免通过 ProxySelector ，或者更确切地说如何获取连接保证没有Java知道的任何代理？

How do I avoid going through the ProxySelector when making a connection with URLConnection or rather how to get a connection guaranteed free of whatever proxies Java knows about ?

我认为这是 Proxy.NO_PROXY 用于。引自Javadoc：

I thought this was what Proxy.NO_PROXY was for. Quoting from the Javadoc:

代表DIRECT连接的代理设置，基本上告诉协议处理程序不使用任何代理

A proxy setting that represents a DIRECT connection, basically telling the protocol handler not to use any proxying

然而，这样的连接仍将通过ProxySelector。我不明白吗？

Yet such a connection will still go through the ProxySelector. I don't get it ??

我做了一个小测试来证明我的观点：

I've made a small test to prove my point:

public static void main(String[] args) throws MalformedURLException, IOException { ProxySelector.setDefault(new MyProxySelector()); URL url = new URL("foobar/x1/x2"); URLConnection connection = url.openConnection(Proxy.NO_PROXY); connection.connect(); }

和一个虚拟的ProxySelector，除了记录正在发生的事情之外什么都不做：

and a dummy ProxySelector which does nothing but log what is going on:

public class MyProxySelector extends ProxySelector { @Override public List<Proxy> select(URI uri) { System.out.println("MyProxySelector called with URI = " + uri); return Collections.singletonList(Proxy.NO_PROXY); } @Override public void connectFailed(URI uri, SocketAddress sa, IOException ioe) {} }

打印：

"MyProxySelector called with URI = socket://foobar:80"

（注意如何协议已从 http 更改为套接字）

(Note how the protocol has changed from http to socket)

我当然可以这样创建我的ProxySelector，以便它总是返回 Proxy.NO_PROXY 如果URI方案是 socket 但我想有可能在网站上有一个SOCKS代理，然后它就不会是真的。

I can of course create my ProxySelector in such a way so that it always returns Proxy.NO_PROXY if the URI scheme is socket but I guess there would be occasions where there's a SOCKS proxy on the site and then it wouldn't be true.

让我重申一个问题：我需要一个方法确保特定的 URLConnection 不使用代理，无论可以设置什么系统属性或安装什么ProxySelector。

Let me restate the question: I need a way to make sure a specific URLConnection doesn't use a proxy, regardless of what System Properties may be set or what ProxySelector is installed.

推荐答案

这被跟踪为 JDK bug 8144008 。