How to prevent this Java code from hanging

Question

I have a list of proxies to test if they are HTTP or Socks proxies, but the Java code below hangs when it calls the connection.getContent() or connection.getInputStream(). I observed that this issue occur when the proxy server fail to respond and the code blocks waiting for response from server, How can I prevent this code from hanging/blocking forever when the server fail to respond, so that the next proxy can be checked.

import java.io.*;
import java.net.*;
import java.util.*;

public class ProxyTest {

    public static void main(String[] args) throws IOException {

        InetSocketAddress proxyAddress = new InetSocketAddress("myproxyaddress", 1234);

        Proxy.Type proxyType = detectProxyType(proxyAddress);
    }

    public static Proxy.Type detectProxyType(InetSocketAddress proxyAddress) throws IOException {

    URL url = new URL("http://www.google.com/");

    List<Proxy.Type> proxyTypesToTry = Arrays.asList(Proxy.Type.SOCKS, Proxy.Type.HTTP);

    for(Proxy.Type proxyType : proxyTypesToTry) {

        Proxy proxy = new Proxy(proxyType, proxyAddress);

        URLConnection connection = null;

        try {

            connection = url.openConnection(proxy);

            connection.setConnectTimeout(10000);
            connection.setReadTimeout(10000);

            connection.getContent();
            //connection.getInputStream();

            return(proxyType);
        }

        catch (SocketException e) {

    e.printStackTrace();
        }
    }

    return(null);
}
}

score 1 · Answer 1 · answered Jul 20 '12 at 19:56

1

To do things in parallel, use threads.

for(Foo f : foos){
    Thread t = new Thread(new Runnable(){
        @Override
        public void run(){
            // blocking call
        }        
    });
    t.start();
}

Better yet, make use of one of the data structures in the java.util.concurrent package.

answered Jul 20 '12 at 19:56

user1329572

6,176
5
29
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I tried this but the thread t will never stop/finish it will hang when connection.getContent() is called. – John Jul 20 '12 at 20:03
+1 for threads suggestion. This is the way to make nonblockign (atleast on the main thread) requests. @john You could always call Thread.interupt() at some interval and have that thread check whether it should stop itself. – hsanders Jul 20 '12 at 20:21

score 0 · Answer 2 · edited May 23 '17 at 12:08

0

I believe there is no and simple straight solution for this. The answer depends on JDK version, implementation and runtime environment. For more details please see Java URLConnection Timeout.

edited May 23 '17 at 12:08

Community

1
1

answered Jul 20 '12 at 20:03

Dmitry B.

9,107
3
43
64

How to prevent this Java code from hanging

2 Answers2