URLConnection throws incorrect exception if address cannot be resolved

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Note: this issue was migrated automatically using bugzilla2github

Original bug ID: BZ#70661
From: @guillerodriguez
Reported version: 0.99

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Comment author: @guillerodriguez

According to the API specification, the URLConnection.connect() method should throw an IOException if an error occurs. However in GNU Classpath if the address can be resolved, an java.nio.channels.UnresolvedAddressException is thrown instead. UnresolvedAddressException is a subclass of IllegalArgumentException, not IOException, so this breaks the API contract.

Here is a sample test case:

import java.net.URL;
import java.net.URLConnection;

public class UnresolvedAddress
{
  public static void main(String args[]) throws Exception
  {
    URL url = new URL("http", "someinvalidsitename.com", 80, "index.html");
    URLConnection connection = url.openConnection();
    connection.setUseCaches(false);
    connection.connect();
  }
}

This results in the following:

Exception in thread "main" java.nio.channels.UnresolvedAddressException
   at gnu.java.nio.SocketChannelImpl.connect(SocketChannelImpl.java:160)
   at gnu.java.net.PlainSocketImpl.connect(PlainSocketImpl.java:281)
   at java.net.Socket.connect(Socket.java:463)
   at java.net.Socket.connect(Socket.java:414)
   at gnu.java.net.protocol.http.HTTPConnection.getSocket(HTTPConnection.java:721)
   at gnu.java.net.protocol.http.HTTPConnection.getOutputStream(HTTPConnection.java:802)
   at gnu.java.net.protocol.http.Request.dispatch(Request.java:292)
   at gnu.java.net.protocol.http.HTTPURLConnection.connect(HTTPURLConnection.java:219)
   at UnresolvedAddress.main(UnresolvedAddress.java:11)

Note that the JDK does the right thing here:

Exception in thread "main" java.net.UnknownHostException: someinvalidsitename.com
  at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:175)
  at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:385)
  at java.net.Socket.connect(Socket.java:546)
  at java.net.Socket.connect(Socket.java:495)
  at sun.net.NetworkClient.doConnect(NetworkClient.java:178)
  at sun.net.www.http.HttpClient.openServer(HttpClient.java:427)
  at sun.net.www.http.HttpClient.openServer(HttpClient.java:529)
  at sun.net.www.http.HttpClient.<init>(HttpClient.java:213)
  at sun.net.www.http.HttpClient.New(HttpClient.java:306)
  at sun.net.www.http.HttpClient.New(HttpClient.java:325)
  at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:955)
  at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:891)
  at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:809)
  at UnresolvedAddress.main(UnresolvedAddress.java:11)

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Comment author: @guillerodriguez

"if the address can be resolved.." should have been "if the address can't be resolved".