<Swing Dev> jdk6 and jdk7: wrong class cast in sun.print.IPPPrintService (in Solaris classes)

[Phil Race]

Why did you send this to the Swing list? Its about printing which is 
handled by 2D.
Please re-send it there : 2d-dev at openjdk.java.net, as I don't want to 
cross-post this.

-phil.

On 11/15/2010 6:40 AM, Nico R. wrote:
> Hello!
>
> In sun.print.IPPPrintService.getIPPConnection(URL), there is a bug with
> class casting: see
>
>
> <URL:http://hg.openjdk.java.net/jdk6/jdk6/jdk/file/5672a2be515a/src/solaris/classes/sun/print/IPPPrintService.java>,
> lines 1556–1565 for JDK 6,
>
> and
>
>
> <URL:http://hg.openjdk.java.net/jdk7/swing/jdk/file/d449b91c56b6/src/solaris/classes/sun/print/IPPPrintService.java>,
> lines 1563–1572 for JDK 7.
>
> The buggy code is:
>
>      public static HttpURLConnection getIPPConnection(URL url) {
>          HttpURLConnection connection;
>          try {
>              connection = (HttpURLConnection)url.openConnection();
>          } catch (java.io.IOException ioe) {
>              return null;
>          }
>          if (!(connection instanceof HttpURLConnection)) {
>              return null;
>          }
>
> If the call to openConnection returns a FileURLConnection (as it does on
> my system), that cannot be cast to an HttpURLConnection. The instanceof
> check happens too late in the code.
>
> What to do: either
>    * catch a ClassCastException and return null from the catch block, or
>    * use a variable of type URLConnection to store the result from
> openConnection(), and cast it to HttpURLConnection /after/ the block
> with the instanceof check.
>
> The problem occurs, because there are URLs like "file:/dev/null" in the
> list or URLs to try. They are retrieved from
> sun.print.CUPSPrinter.getAllPrinters() via
> sun.print.UnixPrintServiceLookup.refreshServices().
>
> I assume this happens for printers that were auto-detected (e.g. via
> ZeroConf etc.) some time ago, but are not accessible at the moment), but
> I am not sure about that.
>
> Perhaps the CUPS system is improperly configured, but this should not
> cause Java applications to throw ClassCastExceptions.
>
> Regards