当HttpURLConnection.connect超时后怎么判断是超时导致的IOException??

Question

如题：
               private HttpURLConnection conn=null;
               ... ...
               try{
URL u = new URL(requestURL);
conn = (HttpURLConnection)u.openConnection();
conn.setDoOutput(true);
conn.setDoInput(true);
conn.setUseCaches(false);
conn.setRequestProperty("Charset","UTF-8");
conn.setRequestProperty("Content-type","text/xml");
conn.setRequestMethod("POST");
conn.setConnectTimeout(CONNECT_TIMEOUT);
conn.setReadTimeout(READ_TIMEOUT);
conn.connect();
... ...
}catch(MalformedURLException e){

return false;
}catch(IOException e){
//此处怎么判断是调用connect方法超时后抛出的IO异常？？
return false;
}catch(ZSException e){

return false;
}catch(Exception e){

return false;
}
finally{
if(conn!=null) conn.disconnect();
}

Answer 1

IOException 内通常都是IO引起的，不需要判断。

Answer 2

SocketTimeoutException - 如果在建立连接之前超时期满 
捕捉这个

Answer 3

观察了下面这个 stack trace 就该知道了吧。
[code=Java]
java.net.SocketTimeoutException: connect timed out
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:352)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:214)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:201)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:377)
at java.net.Socket.connect(Socket.java:530)
at sun.net.NetworkClient.doConnect(NetworkClient.java:170)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:406)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:541)
at sun.net.www.http.HttpClient.<init>(HttpClient.java:245)
at sun.net.www.http.HttpClient.New(HttpClient.java:318)
at sun.net.www.http.HttpClient.New(HttpClient.java:335)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:832)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:773)
at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:698)
at Socket.main(Socket.java:34)</code>