Timeout in DefaultHttpClient

问题:

I'm a little confused on how the timeouts in DefaultHttpClient work.

I'm using this code:

private DefaultHttpClient createHttpClient() {
        HttpParams my_httpParams = new BasicHttpParams();

        HttpConnectionParams.setConnectionTimeout(my_httpParams, 3000);
        HttpConnectionParams.setSoTimeout(my_httpParams, 15000);

        SchemeRegistry registry = new SchemeRegistry();
        registry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));
        ThreadSafeClientConnManager multiThreadedConnectionManager = new ThreadSafeClientConnManager(my_httpParams, registry);

        DefaultHttpClient httpclient = new DefaultHttpClient(multiThreadedConnectionManager, my_httpParams);

        return httpclient;
}

.

String url = "http://www.example.com";

DefaultHttpClient httpclient = createHttpClient();
HttpGet httpget = new HttpGet(url);

try {
    HttpResponse response = httpclient.execute(httpget);
    StatusLine statusLine = response.getStatusLine();
    mStatusCode = statusLine.getStatusCode();

    if (mStatusCode == 200){
        content = EntityUtils.toString(response.getEntity());
    }

} catch (ClientProtocolException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
} catch (IllegalStateException e){
    e.printStackTrace();
}

When 15 seconds have passed and not all data has been received, an exception will be thrown, right? But on which method? I thought it to be the .execute(httpget) method but that one only tells me it throws ClientProtocolException and IOException. Could anyone help me clearifying this?

回答1:

It does throw an exception on execute(). The parent of SocketTimeoutException is an IOException. A catch block handling IOException will be able to catch both.

Try executing this code.

HttpParams my_httpParams = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(my_httpParams, 3000);
HttpConnectionParams.setSoTimeout(my_httpParams, 1);
DefaultHttpClient defaultHttpClient = new DefaultHttpClient(my_httpParams);
HttpGet httpGet = new HttpGet("http://google.com");
defaultHttpClient.execute(httpGet);

It results in this exception.

java.net.SocketTimeoutException: Read timed out
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.read(Unknown Source)
    ...
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:805)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:784)

You can always choose to selectively process the exception by catching it and handling IOException later.

try
{
    // Your code
}
catch (SocketTimeoutException e)
{
    // handle timeouts
    e.printStackTrace();
}
catch (IOException e)
{
    // handle other IO exceptions
    e.printStackTrace();
}

回答2:

If you look at the Apache docs at http://hc.apache.org/httpcomponents-client-ga/tutorial/html/fundamentals.html#d5e249, it notes that connection timeout exceptions are IOException subclasses.

To be more specific, I believe they'll either ConnectTimeoutExceptions if the connection can't be set up within your configured connection timeout, or SocketTimeoutExceptions, if it's set up but no data is received for your configured SO timeout.